Refine Writing Desk collection and ink refill behavior

README.md

@@ -25,15 +25,34 @@ It occupies two adjacent blocks, with one shared inventory; loaded paper and
 the selected page appear on its Legacy-inspired model.
 Desks placed before 0.3.6.1 keep their old one-block footprint until broken
 and placed again; leave an adjacent space when replacing one.
-Its four collection tabs, paper input, ink vial input, empty glass-bottle return,
+Its 88 collection tabs, paper input, ink vial input, empty glass-bottle return,
 16-unit ink meter, and inventory persist
 through world saves; breaking it drops stored contents. The desk screen is a
-functional foundation styled after Legacy's left tabs, central writing surface,
+functional foundation using Legacy's original desk and scrollbar textures.
-and right inventory. Put vanilla paper in the
+Four tabs are visible at once; the controls above and below them move by four
+(1–4, 5–8, through 85–88). Each viewer can browse a different group. Existing
+four-tab desks retain their collections and supplies when upgraded.
+With a notebook selected, pick up a Page from your inventory and click an empty
+position on the left surface to store one page there. Clear search/filter/sort
+and turn off `ALL` to place pages at specific positions; occupied positions are
+never overwritten. A notebook tab exposes all 27 notebook positions (scroll to
+reach the rest); a loose-page tab exposes only its one occupied position.
+Empty tabs have no page storage until a notebook or page is put in the tab slot.
+Click a page on the desk surface to select it for copying. Drag a page from one
+notebook position to an empty position to move it, or onto another page to swap
+their positions. This also works between notebooks shown in the `ALL` view.
+Drag a page out of the panel to turn it back into an item. Drop it over a player
+inventory slot or desk tab to place it there; a tab with a notebook adds it to
+the first open position. Dropping elsewhere leaves the page on the cursor for
+normal inventory placement. The source notebook or tab loses the page only after
+a valid drop.
+Put vanilla paper in the
 upper-left slot and Ink Vials in the upper-right; a copy appears in the
 lower-left result slot when the selected page is valid. Taking it consumes one
-paper and, by default, one ink. An empty meter consumes a vial to refill and
+paper and, by default, one ink. An available vial refills an empty ink meter
-returns a vanilla glass bottle to the lower-right slot. The `AZ` control sorts
+when inserted or when copying uses its last ink, and returns a vanilla glass
+bottle to the lower-right slot. Removing a bottle also retries a blocked refill.
+Refilling waits if that slot is full or contains another item. The `AZ` control sorts
 visible pages by name; `ALL` shows pages held across every desk tab. Search and
 category filtering narrow the view without granting new pages, and cross-tab
 copy selection is checked by the server.

docs/ASSET_PROVENANCE.md

@@ -11,7 +11,8 @@ project's GNU LGPL v3 license. Rivencraft itself uses the same license.
 | `assets/rivencraft/textures/item/writing_desk.png` | `assets/mystcraft/textures/items/writingdesk.png` | `9bc8ddc061845df0cd5ea47f4fdef773cff786ae` | Namespace/path rename only |
 | `assets/rivencraft/textures/block/writing_desk.png` | `assets/mystcraft/textures/entity/desk.png` | `9bc8ddc061845df0cd5ea47f4fdef773cff786ae` | Namespace/path rename only |
 | `assets/rivencraft/textures/block/writing_desk_wood.png` and `writing_desk_inlay.png` | `assets/mystcraft/textures/entity/desk.png` | `9bc8ddc061845df0cd5ea47f4fdef773cff786ae` | Cropped opaque wood and red inlay regions for the two-block model |
-| `assets/rivencraft/textures/gui/writing_desk_legacy.png` | `assets/mystcraft/gui/writingdesk.png` | `9bc8ddc061845df0cd5ea47f4fdef773cff786ae` | Namespace/path rename only; solid GUI backing sampled from Legacy atlas |
+| `assets/rivencraft/textures/gui/writing_desk_legacy.png` | `assets/mystcraft/gui/writingdesk.png` | `9bc8ddc061845df0cd5ea47f4fdef773cff786ae` | Namespace/path rename only; full desk panel, tabs, and cycling controls at original atlas coordinates |
+| `assets/rivencraft/textures/gui/scrollbar.png` | `assets/mystcraft/gui/scrollbar.png` | `9bc8ddc061845df0cd5ea47f4fdef773cff786ae` | Namespace/path rename only; tiled track and normal/pressed thumb |
 | `assets/rivencraft/textures/item/linking_book_unwritten.png` | `assets/mystcraft/textures/items/unlinked.png` | `9bc8ddc061845df0cd5ea47f4fdef773cff786ae` | Namespace/path rename only |
 | `assets/rivencraft/textures/item/page_link_panel.png` | `page_background.png` and `PageBuilder.BasicPageSprite` | `9bc8ddc061845df0cd5ea47f4fdef773cff786ae` | Reproduces the legacy 160 px scale, black panel at `(25,30)`–`(135,75)`, and 128 px resample |
 | `assets/rivencraft/textures/item/page_symbol*.png` and `page_unresolved.png` | `page_background.png`, `textures/symbolcomponents.png`, `WordData`, `ModSymbols`, and `PageBuilder.PageSprite` | `9bc8ddc061845df0cd5ea47f4fdef773cff786ae` | Static 1.21.1 renditions of the legacy runtime-composed four-word symbol pages; `normal_time` uses the legacy Full Length poem |

gradle.properties

@@ -35,7 +35,7 @@ mod_name=Rivencraft
 # The license of the mod. Review your options at https://choosealicense.com/. All Rights Reserved is the default.
 mod_license=LGPL-3.0-or-later
 # The mod version. Rivencraft uses the x.y.z.b policy documented in README.md.
-mod_version=0.3.6.2
+mod_version=0.3.6.8
 immersive_portals_version=6.0.7
 # The group ID for the mod. It is only important when publishing as an artifact to a Maven repository.
 # This should match the base package used for the mod sources.

src/main/java/net/dnorberg/rivencraft/block/entity/WritingDeskBlockEntity.java

@@ -16,18 +16,19 @@ import net.minecraft.world.ContainerHelper;
 import net.minecraft.world.entity.player.Player;
 import net.minecraft.world.item.ItemStack;
 import net.minecraft.world.item.Items;
+import net.minecraft.world.level.Level;
 import net.minecraft.world.level.block.entity.BlockEntity;
 import net.minecraft.world.level.block.state.BlockState;
 
-/** Four collection tabs, paper, ink vials and empty-vial return are owned by the block. */
+/** Collection tabs, paper, ink vials and empty-vial return are owned by the block. */
 public final class WritingDeskBlockEntity extends BlockEntity implements Container {
-    public static final int COLLECTIONS = 4;
+    public static final int COLLECTIONS = 88;
-    public static final int INK = 4;
+    public static final int INK = COLLECTIONS;
-    public static final int RETURN = 5;
+    public static final int RETURN = INK + 1;
-    public static final int PAPER = 6;
+    public static final int PAPER = INK + 2;
     /** Unused by new desks; retained so old saves cannot silently lose slot contents. */
-    public static final int LEGACY_OUTPUT = 7;
+    public static final int LEGACY_OUTPUT = INK + 3;
-    public static final int SIZE = 8;
+    public static final int SIZE = INK + 4;
     private NonNullList<ItemStack> items = NonNullList.withSize(SIZE, ItemStack.EMPTY);
     private int activeCollection;
     private int inkRemaining;
@@ -62,6 +63,7 @@ public final class WritingDeskBlockEntity extends BlockEntity implements Contain
         if (!removed.isEmpty()) {
             if (slot < COLLECTIONS) displayPage = ItemStack.EMPTY;
             setChanged();
+            if (slot == RETURN) refillEmptyInkBar();
         }
         return removed;
     }
@@ -71,6 +73,7 @@ public final class WritingDeskBlockEntity extends BlockEntity implements Contain
         if (stack.getCount() > getMaxStackSize()) stack.setCount(getMaxStackSize());
         if (slot < COLLECTIONS) displayPage = ItemStack.EMPTY;
         setChanged();
+        if (slot == INK || slot == RETURN) refillEmptyInkBar();
     }
     @Override public boolean stillValid(Player player) {
         return level != null && level.isLoaded(worldPosition)
@@ -89,6 +92,28 @@ public final class WritingDeskBlockEntity extends BlockEntity implements Contain
         };
     }
 
+    private boolean hasBottleSpace() {
+        ItemStack returned = items.get(RETURN);
+        return returned.isEmpty() || returned.is(Items.GLASS_BOTTLE)
+                && returned.getCount() < returned.getMaxStackSize();
+    }
+
+    /** Consume one vial only when the empty meter can return its glass bottle. */
+    private void refillEmptyInkBar() {
+        if (level == null || level.isClientSide || inkRemaining != 0 || !hasBottleSpace()) return;
+        ItemStack vial = items.get(INK);
+        if (!vial.is(ModItems.INK_VIAL.get())) return;
+        int ink = Math.clamp(InkVialItem.remaining(vial), 0, InkVialItem.CAPACITY);
+        if (ink == 0) return;
+        inkRemaining = ink;
+        vial.shrink(1);
+        if (vial.isEmpty()) items.set(INK, ItemStack.EMPTY);
+        ItemStack returned = items.get(RETURN);
+        if (returned.isEmpty()) items.set(RETURN, new ItemStack(Items.GLASS_BOTTLE));
+        else returned.grow(1);
+        setChanged();
+    }
+
     /** The output is virtual; inputs are committed only after a result can be given to a player. */
     public boolean canConsumeCopyMaterials() {
         ItemStack paper = items.get(PAPER);
@@ -96,10 +121,8 @@ public final class WritingDeskBlockEntity extends BlockEntity implements Contain
         int cost = WritingInkService.symbolCopyCost();
         if (inkRemaining >= cost) return true;
         ItemStack vial = items.get(INK);
-        ItemStack returned = items.get(RETURN);
         return vial.is(ModItems.INK_VIAL.get()) && inkRemaining + InkVialItem.remaining(vial) >= cost
-                && (returned.isEmpty() || returned.is(Items.GLASS_BOTTLE)
+                && hasBottleSpace();
-                && returned.getCount() < returned.getMaxStackSize());
     }
 
     public boolean consumeCopyMaterials() {
@@ -117,8 +140,13 @@ public final class WritingDeskBlockEntity extends BlockEntity implements Contain
         inkRemaining -= cost;
         removeItem(PAPER, 1);
         setChanged();
+        if (inkRemaining == 0) refillEmptyInkBar();
         return true;
     }
+    @Override public void setLevel(Level level) {
+        super.setLevel(level);
+        refillEmptyInkBar();
+    }
     @Override public void clearContent() {
         items.clear();
         items = NonNullList.withSize(SIZE, ItemStack.EMPTY);
@@ -130,15 +158,25 @@ public final class WritingDeskBlockEntity extends BlockEntity implements Contain
         super.loadAdditional(tag, registries);
         items = NonNullList.withSize(SIZE, ItemStack.EMPTY);
         ContainerHelper.loadAllItems(tag, items, registries);
+        // Pre-88-tab desks stored materials in slots 4..7. Move them once;
+        // never interpret those stacks as newly added collection tabs.
+        if (tag.getInt("InventoryVersion") < 1) {
+            for (int i = 0; i < 4; i++) {
+                items.set(INK + i, items.get(4 + i));
+                items.set(4 + i, ItemStack.EMPTY);
+            }
+        }
         activeCollection = Math.clamp(tag.getInt("ActiveCollection"), 0, COLLECTIONS - 1);
         inkRemaining = Math.clamp(tag.getInt("InkRemaining"), 0, InkVialItem.CAPACITY);
         displayPage = tag.contains("DisplayPage", CompoundTag.TAG_COMPOUND)
                 ? ItemStack.parse(registries, tag.getCompound("DisplayPage")).orElse(ItemStack.EMPTY)
                 : ItemStack.EMPTY;
+        refillEmptyInkBar();
     }
     @Override protected void saveAdditional(CompoundTag tag, HolderLookup.Provider registries) {
         super.saveAdditional(tag, registries);
         ContainerHelper.saveAllItems(tag, items, registries);
+        tag.putInt("InventoryVersion", 1);
         tag.putInt("ActiveCollection", activeCollection);
         tag.putInt("InkRemaining", inkRemaining);
         if (!displayPage.isEmpty()) tag.put("DisplayPage", displayPage.save(registries));

src/main/java/net/dnorberg/rivencraft/client/screen/WritingDeskScreen.java

@@ -7,6 +7,7 @@ import java.util.Comparator;
 import net.dnorberg.rivencraft.Rivencraft;
 import net.dnorberg.rivencraft.item.PageItem;
 import net.dnorberg.rivencraft.menu.WritingDeskMenu;
+import net.dnorberg.rivencraft.block.entity.WritingDeskBlockEntity;
 import net.dnorberg.rivencraft.registry.ModDataComponents;
 import net.dnorberg.rivencraft.registry.ModItems;
 import net.dnorberg.rivencraft.writing.NotebookContents;
@@ -18,14 +19,17 @@ import net.minecraft.client.gui.screens.inventory.AbstractContainerScreen;
 import net.minecraft.network.chat.Component;
 import net.minecraft.resources.ResourceLocation;
 import net.minecraft.world.entity.player.Inventory;
+import net.minecraft.world.inventory.Slot;
 import net.minecraft.world.item.ItemStack;
 
-/** Functional storage surface; full Legacy transcription controls are a later Milestone 4 slice. */
+/** Legacy desk atlas layout, with four visible tabs out of the desk's 88 collections. */
 public final class WritingDeskScreen extends AbstractContainerScreen<WritingDeskMenu> {
     private static final ResourceLocation PAGE_ATLAS = ResourceLocation.fromNamespaceAndPath(
             Rivencraft.MOD_ID, "textures/gui/notebook_pages.png");
     private static final ResourceLocation LEGACY_DESK = ResourceLocation.fromNamespaceAndPath(
             Rivencraft.MOD_ID, "textures/gui/writing_desk_legacy.png");
+    private static final ResourceLocation SCROLLBAR = ResourceLocation.fromNamespaceAndPath(
+            Rivencraft.MOD_ID, "textures/gui/scrollbar.png");
     private int lastCollection = -1;
     private int selectedPage;
     private int scrollRows;
@@ -39,11 +43,20 @@ public final class WritingDeskScreen extends AbstractContainerScreen<WritingDesk
     private Button sortButton;
     private boolean draggingScrollbar;
     private record DisplayPage(int collection, int index, ItemStack stack) {}
+    private DisplayPage pageDragSource;
+    private double pageDragStartX;
+    private double pageDragStartY;
+    private boolean draggingPage;
+
+    private boolean isPhysicalPageView() {
+        return !allMode && !sortAlphabetically && selectedCategory == null
+                && (search == null || search.getValue().isBlank());
+    }
 
     public WritingDeskScreen(WritingDeskMenu menu, Inventory inventory, Component title) {
         super(menu, inventory, title);
-        imageWidth = 398;
+        imageWidth = 409;
-        imageHeight = 176;
+        imageHeight = 186;
         titleLabelX = 222;
     }
 
@@ -52,7 +65,7 @@ public final class WritingDeskScreen extends AbstractContainerScreen<WritingDesk
         sortButton = addRenderableWidget(Button.builder(Component.literal("AZ"), button -> {
             sortAlphabetically = !sortAlphabetically;
             scrollRows = 0;
-        }).bounds(leftPos + 58, topPos - 18, 20, 18).build());
+        }).bounds(leftPos + 58, topPos, 20, 18).build());
         allButton = addRenderableWidget(Button.builder(Component.literal("ALL"), button -> {
             allMode = !allMode;
             scrollRows = 0;
@@ -60,10 +73,10 @@ public final class WritingDeskScreen extends AbstractContainerScreen<WritingDesk
                 selectedCollection = -1;
                 selectedPage = 0;
                 if (minecraft != null && minecraft.gameMode != null)
-                    minecraft.gameMode.handleInventoryButtonClick(menu.containerId, menu.activeCollection());
+                    minecraft.gameMode.handleInventoryButtonClick(menu.containerId, WritingDeskMenu.PAGE_BUTTON_BASE);
             }
-        }).bounds(leftPos + 80, topPos - 18, 28, 18).build());
+        }).bounds(leftPos + 80, topPos, 28, 18).build());
-        search = new EditBox(font, leftPos + 110, topPos - 18, 86, 18,
+        search = new EditBox(font, leftPos + 110, topPos, 101, 18,
                 Component.translatable("screen.rivencraft.writing_desk.search"));
         search.setMaxLength(64);
         search.setHint(Component.translatable("screen.rivencraft.writing_desk.search"));
@@ -76,20 +89,22 @@ public final class WritingDeskScreen extends AbstractContainerScreen<WritingDesk
             selectedCategory = next >= categories.size() ? null : categories.get(next);
             categoryButton.setMessage(Component.literal(selectedCategory == null ? "C" : "C*"));
             scrollRows = 0;
-        }).bounds(leftPos + 198, topPos - 18, 18, 18).build());
+        }).bounds(leftPos + 213, topPos, 18, 18).build());
     }
 
     private List<DisplayPage> filteredPages() {
         String query = search == null ? "" : search.getValue().trim().toLowerCase(Locale.ROOT);
         List<DisplayPage> entries = new ArrayList<>();
         int from = allMode ? 0 : menu.activeCollection();
-        int until = allMode ? 4 : from + 1;
+        int until = allMode ? WritingDeskBlockEntity.COLLECTIONS : from + 1;
         for (int collection = from; collection < until; collection++) {
             List<ItemStack> pages = pages(collection);
             int last = -1;
             for (int i = 0; i < pages.size(); i++) if (!pages.get(i).isEmpty()) last = i;
+            // A notebook has exactly its normal GUI capacity; a loose page has one position.
+            if (isPhysicalPageView()) last = menu.pageCapacity(collection) - 1;
             for (int i = 0; i <= last; i++) {
-                ItemStack page = pages.get(i);
+                ItemStack page = i < pages.size() ? pages.get(i) : ItemStack.EMPTY;
                 if (page.isEmpty() && (allMode || sortAlphabetically || !query.isEmpty() || selectedCategory != null)) continue;
                 if (!page.isEmpty() && !query.isEmpty()
                         && !page.getHoverName().getString().toLowerCase(Locale.ROOT).contains(query)
@@ -118,47 +133,48 @@ public final class WritingDeskScreen extends AbstractContainerScreen<WritingDesk
     @Override protected void renderBg(GuiGraphics graphics, float partialTick, int mouseX, int mouseY) {
         int x = leftPos;
         int y = topPos;
-        graphics.fill(x + 56, y + 14, x + 206, y + 168, 0xAA201B18);
+        // Legacy GuiWritingDesk draws the entire 176x166 panel, not a stretched swatch.
-        graphics.blit(LEGACY_DESK, x, y + 5, 56, 9, 0, 166, 56, 9, 256, 256);
+        graphics.blit(LEGACY_DESK, x + 233, y + 20, 0, 0, 176, 166);
-        graphics.blit(LEGACY_DESK, x, y + 166, 56, 9, 0, 215, 56, 9, 256, 256);
+        drawTabControl(graphics, 20, 203, menu.firstVisibleTab() > 0);
-        graphics.blit(LEGACY_DESK, x + 218, y + 4, 178, 170, 64, 8, 16, 16, 256, 256);
         for (int i = 0; i < 4; i++) {
-            graphics.blit(LEGACY_DESK, x, y + 16 + i * 37,
+            int tab = menu.firstVisibleTab() + i;
-                    56, 36, 0, 166, 56, 54, 256, 256);
+            int tabY = y + 29 + i * 37;
-            if (i == menu.activeCollection() && !allMode)
+            if (tab == menu.activeCollection() && !allMode) graphics.setColor(0.5F, 0.5F, 1F, 1F);
-                graphics.fill(x + 2, y + 18 + i * 37, x + 54, y + 46 + i * 37, 0x885858CC);
+            graphics.blit(LEGACY_DESK, x, tabY, 0, 166, 58, 37);
-            graphics.drawString(font, new String[]{"I", "II", "III", "IV"}[i],
+            graphics.setColor(1F, 1F, 1F, 1F);
-                    x + 8, y + 25 + i * 37, 0xFF181818, false);
+            graphics.drawString(font, Integer.toString(tab + 1), x + 8, tabY + 8, 0xFF181818, false);
-            slotFrame(graphics, 36, 20 + i * 37);
+            ItemStack collection = menu.getSlot(tab).getItem();
+            if (!collection.isEmpty()) {
+                String name = collection.getHoverName().getString();
+                float scale = Math.min(1F, 50F / Math.max(1, font.width(name)));
+                graphics.pose().pushPose();
+                graphics.pose().translate(x + 4, tabY + 25, 0);
+                graphics.pose().scale(scale, scale, 1);
+                graphics.drawString(font, name, 0, 0, 0xFF404040, false);
+                graphics.pose().popPose();
+            }
         }
-        graphics.blit(LEGACY_DESK, x + 206, y + 14, 10, 130, 177, 0, 12, 166, 256, 256);
+        drawTabControl(graphics, 177, 212, menu.firstVisibleTab() < WritingDeskBlockEntity.COLLECTIONS - 4);
+        // GuiElementVSlider: 4-pixel caps, repeated 22-pixel track, 12x15 thumb.
+        graphics.blit(SCROLLBAR, x + 213, y + 20, 0, 0, 20, 4, 32, 32);
+        for (int offset = 4; offset < 162; offset += 22)
+            graphics.blit(SCROLLBAR, x + 213, y + 20 + offset, 0, 4, 20, Math.min(22, 162 - offset), 32, 32);
+        graphics.blit(SCROLLBAR, x + 213, y + 182, 0, 26, 20, 4, 32, 32);
         int totalRows = (filteredPages().size() + 4) / 5;
-        int maxScroll = Math.max(0, totalRows - 3);
+        int maxScroll = Math.max(0, totalRows - 4);
         scrollRows = Math.clamp(scrollRows, 0, maxScroll);
-        int thumbHeight = Math.max(14, 126 * 3 / Math.max(3, totalRows));
+        int thumbY = y + 24 + (maxScroll == 0 ? 0 : scrollRows * 143 / maxScroll);
-        int thumbY = y + 16 + (maxScroll == 0 ? 0 : scrollRows * (126 - thumbHeight) / maxScroll);
+        graphics.blit(SCROLLBAR, x + 217, thumbY, 20, draggingScrollbar ? 15 : 0, 12, 15, 32, 32);
-        graphics.fill(x + 207, thumbY, x + 215, thumbY + thumbHeight, 0xFFB7B7B7);
+        graphics.fill(x + 365, y + 27, x + 381, y + 97, 0xFF303035);
-        graphics.renderOutline(x + 207, thumbY, 8, thumbHeight, 0xFF424242);
+        graphics.fill(x + 366, y + 28, x + 380, y + 96, 0xFF6666AA);
-        slotFrame(graphics, 370, 9);
+        int filled = 68 * menu.inkRemaining() / 16;
-        slotFrame(graphics, 228, 9);
+        if (filled > 0) graphics.fill(x + 366, y + 96 - filled, x + 380, y + 96, 0xFF15151B);
-        slotFrame(graphics, 228, 57);
-        slotFrame(graphics, 370, 57);
-        graphics.fill(x + 350, y + 9, x + 364, y + 64, 0xFF303035);
-        graphics.fill(x + 352, y + 11, x + 362, y + 62, 0xFF15151B);
-        int filled = 51 * menu.inkRemaining() / 16;
-        if (filled > 0) graphics.fill(x + 352, y + 62 - filled, x + 362, y + 62, 0xFF6666AA);
-        graphics.renderOutline(x + 350, y + 9, 14, 55, 0xFF484848);
-        for (int row = 0; row < 3; row++) {
-            for (int column = 0; column < 9; column++) slotFrame(graphics, 224 + column * 18, 79 + row * 18);
-        }
-        for (int column = 0; column < 9; column++) slotFrame(graphics, 224 + column * 18, 137);
     }
 
-    private void slotFrame(GuiGraphics graphics, int x, int y) {
+    private void drawTabControl(GuiGraphics graphics, int y, int textureY, boolean enabled) {
-        graphics.fill(leftPos + x - 1, topPos + y - 1,
+        if (!enabled) graphics.setColor(0.4F, 0.4F, 0.4F, 1F);
-                leftPos + x + 17, topPos + y + 17, 0xFF4D4D4D);
+        graphics.blit(LEGACY_DESK, leftPos, topPos + y, 0, textureY, 58, 9);
-        graphics.fill(leftPos + x, topPos + y,
+        graphics.setColor(1F, 1F, 1F, 1F);
-                leftPos + x + 16, topPos + y + 16, 0xFF858585);
     }
 
     @Override protected void renderLabels(GuiGraphics graphics, int mouseX, int mouseY) {
@@ -167,17 +183,26 @@ public final class WritingDeskScreen extends AbstractContainerScreen<WritingDesk
 
     @Override public void render(GuiGraphics graphics, int mouseX, int mouseY, float partialTick) {
         super.render(graphics, mouseX, mouseY, partialTick);
-        if (sortAlphabetically) graphics.renderOutline(leftPos + 58, topPos - 18, 20, 18, 0xFFFFD061);
+        if (sortAlphabetically) graphics.renderOutline(leftPos + 58, topPos, 20, 18, 0xFFFFD061);
-        if (allMode) graphics.renderOutline(leftPos + 80, topPos - 18, 28, 18, 0xFFFFD061);
+        if (allMode) graphics.renderOutline(leftPos + 80, topPos, 28, 18, 0xFFFFD061);
         renderCollection(graphics);
+        if (draggingPage && pageDragSource != null) {
+            DisplayPage target = pageAtMouse(mouseX, mouseY);
+            if (target != null && canMovePage(pageDragSource, target)) {
+                int x = leftPos + 58 + ((int) mouseX - leftPos - 58) / 31 * 31;
+                int y = topPos + 20 + ((int) mouseY - topPos - 20) / 41 * 41;
+                graphics.renderOutline(x, y, 30, 40, 0xFF57D478);
+            }
+            graphics.renderItem(pageDragSource.stack(), mouseX - 8, mouseY - 8);
+        }
         renderTooltip(graphics, mouseX, mouseY);
-        if (mouseX >= leftPos + 350 && mouseX < leftPos + 364
+        if (mouseX >= leftPos + 365 && mouseX < leftPos + 381
-                && mouseY >= topPos + 9 && mouseY < topPos + 64) {
+                && mouseY >= topPos + 27 && mouseY < topPos + 97) {
             graphics.renderTooltip(font, Component.translatable("screen.rivencraft.writing_desk.ink",
                     menu.inkRemaining(), 16), mouseX, mouseY);
         }
-        if (mouseX >= leftPos + 198 && mouseX < leftPos + 216
+        if (mouseX >= leftPos + 213 && mouseX < leftPos + 231
-                && mouseY >= topPos - 18 && mouseY < topPos) {
+                && mouseY >= topPos && mouseY < topPos + 18) {
             graphics.renderTooltip(font, Component.literal(selectedCategory == null
                     ? "All categories" : selectedCategory.toString()), mouseX, mouseY);
         }
@@ -200,13 +225,13 @@ public final class WritingDeskScreen extends AbstractContainerScreen<WritingDesk
             selectedCollection = -1;
         }
         List<DisplayPage> entries = filteredPages();
-        for (int i = scrollRows * 5; i < entries.size() && i < scrollRows * 5 + 15; i++) {
+        for (int i = scrollRows * 5; i < entries.size() && i < scrollRows * 5 + 20; i++) {
             int column = i % 5;
             int row = i / 5 - scrollRows;
             DisplayPage entry = entries.get(i);
             ItemStack page = entry.stack();
-            int x = leftPos + 58 + column * 29;
+            int x = leftPos + 58 + column * 31;
-            int y = topPos + 18 + row * 41;
+            int y = topPos + 20 + row * 41;
             drawPage(graphics, page, x, y);
             if (page.isEmpty()) graphics.fill(x, y, x + 30, y + 40, 0xB8000000);
             int active = selectedCollection >= 0 ? selectedCollection : menu.activeCollection();
@@ -217,10 +242,10 @@ public final class WritingDeskScreen extends AbstractContainerScreen<WritingDesk
         List<ItemStack> source = pages(active);
         if (selectedPage >= source.size() || source.get(selectedPage).isEmpty()) return;
         ItemStack selected = source.get(selectedPage);
-        drawPage(graphics, selected, leftPos + 253, topPos + 10);
+        drawPage(graphics, selected, leftPos + 265, topPos + 26);
-        String title = font.plainSubstrByWidth(selected.getHoverName().getString(), 84);
+        String title = font.plainSubstrByWidth(selected.getHoverName().getString(), 95);
-        graphics.fill(leftPos + 251, topPos + 58, leftPos + 342, topPos + 73, 0xFF202020);
+        graphics.fill(leftPos + 261, topPos + 81, leftPos + 360, topPos + 95, 0xFF202020);
-        graphics.drawString(font, title, leftPos + 254, topPos + 61, 0xFFE0E0E0, false);
+        graphics.drawString(font, title, leftPos + 263, topPos + 84, 0xFFE0E0E0, false);
     }
 
     private void drawPage(GuiGraphics graphics, ItemStack page, int x, int y) {
@@ -234,44 +259,116 @@ public final class WritingDeskScreen extends AbstractContainerScreen<WritingDesk
         }
     }
 
+    private DisplayPage pageAtMouse(double mouseX, double mouseY) {
+        int x = (int) Math.floor(mouseX - leftPos - 58);
+        int y = (int) Math.floor(mouseY - topPos - 20);
+        if (x < 0 || x >= 155 || y < 0 || y >= 164 || x % 31 >= 30 || y % 41 >= 40) return null;
+        int index = (y / 41 + scrollRows) * 5 + x / 31;
+        List<DisplayPage> entries = filteredPages();
+        return index < entries.size() ? entries.get(index) : null;
+    }
+
+    private boolean canMovePage(DisplayPage source, DisplayPage target) {
+        return !source.stack().isEmpty()
+                && (menu.getSlot(source.collection()).getItem().is(ModItems.NOTEBOOK.get())
+                    || menu.getSlot(source.collection()).getItem().is(ModItems.PAGE.get()))
+                && (menu.getSlot(target.collection()).getItem().is(ModItems.NOTEBOOK.get())
+                    || menu.getSlot(target.collection()).getItem().is(ModItems.PAGE.get()))
+                && (source.collection() != target.collection() || source.index() != target.index());
+    }
+
+    private int extractTargetSlot(double mouseX, double mouseY) {
+        for (Slot slot : menu.slots) {
+            int index = slot.index;
+            if (index >= WritingDeskBlockEntity.COLLECTIONS && index <= WritingDeskMenu.COPY_RESULT) continue;
+            if (!slot.isActive() || !isHovering(slot.x, slot.y, 16, 16, mouseX, mouseY)) continue;
+            ItemStack held = pageDragSource.stack();
+            if (!slot.mayPlace(held)) return -1;
+            ItemStack current = slot.getItem();
+            if (current.isEmpty()) return index;
+            if (index < WritingDeskBlockEntity.COLLECTIONS && current.is(ModItems.NOTEBOOK.get())) {
+                List<ItemStack> pages = current.getOrDefault(
+                        ModDataComponents.NOTEBOOK_CONTENTS.get(), NotebookContents.EMPTY).pages();
+                if (pages.size() < NotebookContents.MAX_PAGES || pages.stream().anyMatch(ItemStack::isEmpty))
+                    return index;
+            } else if (index > WritingDeskMenu.COPY_RESULT && ItemStack.isSameItemSameComponents(current, held)
+                    && current.getCount() < slot.getMaxStackSize(held)) return index;
+            return -1;
+        }
+        return -1;
+    }
+
     @Override public boolean mouseClicked(double mouseX, double mouseY, int button) {
         if (button == 0) {
-            if (mouseX >= leftPos + 206 && mouseX < leftPos + 217
+            pageDragSource = null;
-                    && mouseY >= topPos + 14 && mouseY < topPos + 144) {
+            draggingPage = false;
+        }
+        int surfaceX = (int) Math.floor(mouseX - leftPos - 58);
+        int surfaceY = (int) Math.floor(mouseY - topPos - 20);
+        if ((button == 0 || button == 1) && !menu.getCarried().isEmpty()
+                && surfaceX >= 0 && surfaceX < 155 && surfaceY >= 0 && surfaceY < 164) {
+            if (menu.getCarried().is(ModItems.PAGE.get()) && surfaceX % 31 < 30 && surfaceY % 41 < 40) {
+                int index = (surfaceY / 41 + scrollRows) * 5 + surfaceX / 31;
+                List<DisplayPage> entries = filteredPages();
+                // Only displayed positions are addressable. Filtering never turns
+                // empty screen space into additional storage for a loose-page tab.
+                int collection = index < entries.size() ? entries.get(index).collection() : menu.activeCollection();
+                int page = index < entries.size() ? entries.get(index).index() : index;
+                if (index < entries.size() && page < menu.pageCapacity(collection)
+                        && minecraft != null && minecraft.gameMode != null) {
+                    minecraft.gameMode.handleInventoryButtonClick(menu.containerId,
+                            WritingDeskMenu.PLACE_PAGE_BUTTON_BASE + collection * NotebookContents.MAX_PAGES + page);
+                }
+            }
+            return true;
+        }
+        if (button == 0) {
+            if (mouseX >= leftPos && mouseX < leftPos + 58) {
+                int y = (int) mouseY - topPos;
+                if (y >= 20 && y < 29 || y >= 177 && y < 186) {
+                    if (minecraft != null && minecraft.gameMode != null)
+                        minecraft.gameMode.handleInventoryButtonClick(menu.containerId,
+                                y < 29 ? WritingDeskMenu.PREVIOUS_TABS : WritingDeskMenu.NEXT_TABS);
+                    return true;
+                }
+            }
+            if (mouseX >= leftPos + 213 && mouseX < leftPos + 233
+                    && mouseY >= topPos + 20 && mouseY < topPos + 186) {
                 draggingScrollbar = true;
                 setScrollFromMouse(mouseY);
                 return true;
             }
-            int x = (int) mouseX - leftPos - 58;
+            int x = (int) Math.floor(mouseX - leftPos - 58);
-            int y = (int) mouseY - topPos - 18;
+            int y = (int) Math.floor(mouseY - topPos - 20);
-            if (x >= 0 && x < 145 && y >= 0 && y < 123) {
+            if (x >= 0 && x < 155 && y >= 0 && y < 164) {
-                int column = x / 29;
+                DisplayPage entry = pageAtMouse(mouseX, mouseY);
-                int row = y / 41;
+                if (entry != null && !entry.stack().isEmpty()) {
-                int index = (row + scrollRows) * 5 + column;
+                    selectedCollection = entry.collection();
-                List<DisplayPage> entries = filteredPages();
+                    selectedPage = entry.index();
-                if (y % 41 < 40 && index < entries.size()) {
+                    if (menu.getCarried().isEmpty()) {
-                    DisplayPage entry = entries.get(index);
+                        pageDragSource = entry;
-                    if (!entry.stack().isEmpty()) {
+                        pageDragStartX = mouseX;
-                        selectedCollection = entry.collection();
+                        pageDragStartY = mouseY;
-                        selectedPage = entry.index();
+                    }
-                        if (minecraft != null && minecraft.gameMode != null) {
+                    if (minecraft != null && minecraft.gameMode != null) {
-                            int id = allMode ? 1000 + entry.collection() * NotebookContents.MAX_PAGES + entry.index()
+                        int id = WritingDeskMenu.ALL_PAGE_BUTTON_BASE
-                                    : 16 + entry.index();
+                                + entry.collection() * NotebookContents.MAX_PAGES + entry.index();
-                            minecraft.gameMode.handleInventoryButtonClick(menu.containerId, id);
+                        minecraft.gameMode.handleInventoryButtonClick(menu.containerId, id);
-                        }
                     }
                 }
                 return true;
             }
         }
-        if (button == 0 && mouseX >= leftPos && mouseX < leftPos + 35) {
+        if (button == 0 && mouseX >= leftPos && mouseX < leftPos + 58) {
             for (int i = 0; i < 4; i++) {
-                int top = topPos + 16 + i * 37;
+                int top = topPos + 29 + i * 37;
-                if (mouseY >= top && mouseY < top + 36) {
+                boolean overSlot = mouseX >= leftPos + 36 && mouseX < leftPos + 54
+                        && mouseY >= top + 4 && mouseY < top + 22;
+                if (mouseY >= top && mouseY < top + 37 && !overSlot) {
                     allMode = false;
                     selectedCollection = -1;
                     if (minecraft != null && minecraft.gameMode != null) {
-                        minecraft.gameMode.handleInventoryButtonClick(menu.containerId, i);
+                        minecraft.gameMode.handleInventoryButtonClick(menu.containerId, menu.firstVisibleTab() + i);
                     }
                     return true;
                 }
@@ -281,10 +378,10 @@ public final class WritingDeskScreen extends AbstractContainerScreen<WritingDesk
     }
 
     @Override public boolean mouseScrolled(double mouseX, double mouseY, double scrollX, double scrollY) {
-        if (mouseX >= leftPos + 58 && mouseX < leftPos + 217
+        if (mouseX >= leftPos + 58 && mouseX < leftPos + 233
-                && mouseY >= topPos + 18 && mouseY < topPos + 141) {
+                && mouseY >= topPos + 20 && mouseY < topPos + 186) {
             int rows = (filteredPages().size() + 4) / 5;
-            scrollRows = Math.clamp(scrollRows - (int) Math.signum(scrollY), 0, Math.max(0, rows - 3));
+            scrollRows = Math.clamp(scrollRows - (int) Math.signum(scrollY), 0, Math.max(0, rows - 4));
             return true;
         }
         return super.mouseScrolled(mouseX, mouseY, scrollX, scrollY);
@@ -292,11 +389,16 @@ public final class WritingDeskScreen extends AbstractContainerScreen<WritingDesk
 
     private void setScrollFromMouse(double mouseY) {
         int rows = (filteredPages().size() + 4) / 5;
-        int max = Math.max(0, rows - 3);
+        int max = Math.max(0, rows - 4);
-        scrollRows = Math.clamp((int) Math.round((mouseY - topPos - 16) * max / 126.0), 0, max);
+        scrollRows = Math.clamp((int) Math.round((mouseY - topPos - 31.5) * max / 143.0), 0, max);
     }
 
     @Override public boolean mouseDragged(double mouseX, double mouseY, int button, double dragX, double dragY) {
+        if (button == 0 && pageDragSource != null) {
+            if (Math.abs(mouseX - pageDragStartX) >= 4 || Math.abs(mouseY - pageDragStartY) >= 4)
+                draggingPage = true;
+            return true;
+        }
         if (button == 0 && draggingScrollbar) {
             setScrollFromMouse(mouseY);
             return true;
@@ -305,6 +407,27 @@ public final class WritingDeskScreen extends AbstractContainerScreen<WritingDesk
     }
 
     @Override public boolean mouseReleased(double mouseX, double mouseY, int button) {
+        if (button == 0 && pageDragSource != null) {
+            if (draggingPage) {
+                DisplayPage target = pageAtMouse(mouseX, mouseY);
+                if (target != null && canMovePage(pageDragSource, target)
+                        && minecraft != null && minecraft.gameMode != null) {
+                    selectedCollection = target.collection();
+                    selectedPage = target.index();
+                    minecraft.gameMode.handleInventoryButtonClick(menu.containerId,
+                            WritingDeskMenu.movePageButtonId(pageDragSource.collection(), pageDragSource.index(),
+                                    target.collection(), target.index()));
+                } else if (target == null && minecraft != null && minecraft.gameMode != null) {
+                    int targetSlot = extractTargetSlot(mouseX, mouseY);
+                    minecraft.gameMode.handleInventoryButtonClick(menu.containerId,
+                            WritingDeskMenu.extractPageButtonId(pageDragSource.collection(), pageDragSource.index(),
+                                    targetSlot));
+                }
+            }
+            pageDragSource = null;
+            draggingPage = false;
+            return true;
+        }
         if (button == 0 && draggingScrollbar) {
             draggingScrollbar = false;
             return true;

src/main/java/net/dnorberg/rivencraft/gametest/WritingDeskGameTests.java

@@ -61,10 +61,10 @@ public final class WritingDeskGameTests {
         helper.getLevel().setBlock(pos, Blocks.AIR.defaultBlockState(), 3);
         var drops = helper.getLevel().getEntitiesOfClass(ItemEntity.class, new AABB(pos).inflate(2));
         int notebooks = drops.stream().filter(e -> e.getItem().is(ModItems.NOTEBOOK.get())).mapToInt(e -> e.getItem().getCount()).sum();
-        int ink = drops.stream().filter(e -> e.getItem().is(ModItems.INK_VIAL.get())).mapToInt(e -> e.getItem().getCount()).sum();
+        int bottles = drops.stream().filter(e -> e.getItem().is(Items.GLASS_BOTTLE)).mapToInt(e -> e.getItem().getCount()).sum();
         int pages = drops.stream().filter(e -> e.getItem().is(Items.PAPER)).mapToInt(e -> e.getItem().getCount()).sum();
         helper.assertValueEqual(notebooks, 1, "Notebook must drop exactly once");
-        helper.assertValueEqual(ink, 1, "Ink must drop exactly once");
+        helper.assertValueEqual(bottles, 1, "Consumed vial must return one glass bottle on break");
         helper.assertValueEqual(pages, 12, "Pages must drop without loss");
         helper.succeed();
     }
@@ -81,7 +81,7 @@ public final class WritingDeskGameTests {
         helper.assertTrue(menu.stillValid(player), "Placed desk must keep its menu valid");
         helper.assertTrue(menu.clickMenuButton(player, 3), "Active collection control must accept a valid tab");
         helper.assertValueEqual(desk.activeCollection(), 3, "Selected tab must be stored on the desk");
-        menu.quickMoveStack(player, 9);
+        menu.quickMoveStack(player, WritingDeskMenu.COPY_RESULT + 1);
         helper.assertValueEqual(desk.getItem(WritingDeskBlockEntity.PAPER).getCount(), 12, "Shift-click must deposit all pages");
         helper.assertTrue(player.getInventory().getItem(9).isEmpty(), "Shift-click must consume player source stack");
         menu.quickMoveStack(player, WritingDeskBlockEntity.PAPER);
@@ -111,12 +111,12 @@ public final class WritingDeskGameTests {
                 "A source page with paper and ink must preview one copy");
         helper.assertValueEqual(desk.getItem(WritingDeskBlockEntity.PAPER).getCount(), 2,
                 "Previewing must not consume paper");
-        helper.assertValueEqual(desk.inkRemaining(), 0, "Previewing must not consume ink");
+        helper.assertValueEqual(desk.inkRemaining(), 16, "Inserting a vial must fill the empty bar before copying");
         menu.clicked(WritingDeskMenu.COPY_RESULT, 0, ClickType.PICKUP, player);
         helper.assertTrue(menu.getCarried().is(ModItems.PAGE.get()), "Taking result must give the copied page");
         helper.assertValueEqual(desk.getItem(WritingDeskBlockEntity.PAPER).getCount(), 1,
                 "Taking a copy must consume one paper");
-        helper.assertValueEqual(desk.inkRemaining(), 15, "First copy must refill to 16 and consume one ink");
+        helper.assertValueEqual(desk.inkRemaining(), 15, "First copy must consume one ink");
         helper.assertTrue(desk.getItem(WritingDeskBlockEntity.INK).isEmpty(), "Refill must consume one vial");
         helper.assertTrue(desk.getItem(WritingDeskBlockEntity.RETURN).is(Items.GLASS_BOTTLE),
                 "Refill must return a vanilla glass bottle");
@@ -135,6 +135,48 @@ public final class WritingDeskGameTests {
         helper.succeed();
     }
 
+    @GameTest(template = "empty")
+    public static void emptyDeskInkBarRefillsWithoutCopying(GameTestHelper helper) {
+        BlockPos pos = helper.absolutePos(new BlockPos(1, 1, 1));
+        helper.getLevel().setBlock(pos, ModBlocks.WRITING_DESK.get().defaultBlockState(), 3);
+        WritingDeskBlockEntity desk = (WritingDeskBlockEntity) helper.getLevel().getBlockEntity(pos);
+        desk.setItem(WritingDeskBlockEntity.INK, new ItemStack(ModItems.INK_VIAL.get(), 2));
+        helper.assertValueEqual(desk.inkRemaining(), 16, "Inserting a vial must refill immediately");
+        helper.assertValueEqual(desk.getItem(WritingDeskBlockEntity.INK).getCount(), 1,
+                "Refill must consume exactly one vial");
+        helper.assertTrue(desk.getItem(WritingDeskBlockEntity.RETURN).is(Items.GLASS_BOTTLE),
+                "Refill must put a vanilla glass bottle in the return slot");
+        helper.runAfterDelay(2, () -> {
+            helper.assertValueEqual(desk.inkRemaining(), 16, "Full bar must not refill again");
+            helper.assertValueEqual(desk.getItem(WritingDeskBlockEntity.INK).getCount(), 1,
+                    "Full bar must leave the second vial untouched");
+            helper.assertValueEqual(desk.getItem(WritingDeskBlockEntity.RETURN).getCount(), 1,
+                    "Full bar must not create another bottle");
+            helper.succeed();
+        });
+    }
+
+    @GameTest(template = "empty")
+    public static void emptyDeskInkBarWaitsForBottleSpace(GameTestHelper helper) {
+        BlockPos pos = helper.absolutePos(new BlockPos(1, 1, 1));
+        helper.getLevel().setBlock(pos, ModBlocks.WRITING_DESK.get().defaultBlockState(), 3);
+        WritingDeskBlockEntity desk = (WritingDeskBlockEntity) helper.getLevel().getBlockEntity(pos);
+        desk.setItem(WritingDeskBlockEntity.RETURN, new ItemStack(Items.GLASS_BOTTLE, 64));
+        desk.setItem(WritingDeskBlockEntity.INK, new ItemStack(ModItems.INK_VIAL.get()));
+        helper.assertValueEqual(desk.inkRemaining(), 0, "Full bottle slot must block automatic refill");
+        helper.assertTrue(desk.getItem(WritingDeskBlockEntity.INK).is(ModItems.INK_VIAL.get()),
+                "Blocked refill must preserve the vial");
+        helper.assertValueEqual(desk.getItem(WritingDeskBlockEntity.RETURN).getCount(), 64,
+                "Blocked refill must preserve the bottle stack");
+        desk.removeItem(WritingDeskBlockEntity.RETURN, 1);
+        helper.assertValueEqual(desk.inkRemaining(), 16, "Removing a bottle must immediately permit refill");
+        helper.assertTrue(desk.getItem(WritingDeskBlockEntity.INK).isEmpty(),
+                "Refill must consume the waiting vial");
+        helper.assertValueEqual(desk.getItem(WritingDeskBlockEntity.RETURN).getCount(), 64,
+                "Refill must return one glass bottle to the available space");
+        helper.succeed();
+    }
+
     @GameTest(template = "empty")
     public static void shiftClickCopiesOnlyWhenResourcesAndBottleSpaceExist(GameTestHelper helper) {
         BlockPos pos = helper.absolutePos(new BlockPos(1, 1, 1));
@@ -142,8 +184,8 @@ public final class WritingDeskGameTests {
         WritingDeskBlockEntity desk = (WritingDeskBlockEntity) helper.getLevel().getBlockEntity(pos);
         desk.setItem(0, PageItem.createLinkPanelPage());
         desk.setItem(WritingDeskBlockEntity.PAPER, new ItemStack(Items.PAPER, 2));
-        desk.setItem(WritingDeskBlockEntity.INK, new ItemStack(ModItems.INK_VIAL.get()));
         desk.setItem(WritingDeskBlockEntity.RETURN, new ItemStack(Items.GLASS_BOTTLE, 64));
+        desk.setItem(WritingDeskBlockEntity.INK, new ItemStack(ModItems.INK_VIAL.get()));
         var player = helper.makeMockServerPlayerInLevel();
         player.moveTo(pos.getX() + 0.5, pos.getY() + 0.5, pos.getZ() + 0.5);
         WritingDeskMenu menu = new WritingDeskMenu(1, player.getInventory(), desk);
@@ -180,7 +222,7 @@ public final class WritingDeskGameTests {
         menu.broadcastChanges();
         helper.assertTrue(menu.getSlot(WritingDeskMenu.COPY_RESULT).getItem().isEmpty(),
                 "An empty selected position must not create a copy");
-        helper.assertTrue(menu.clickMenuButton(player, 17), "Second page selection must be accepted");
+        helper.assertTrue(menu.clickMenuButton(player, WritingDeskMenu.PAGE_BUTTON_BASE + 1), "Second page selection must be accepted");
         menu.broadcastChanges();
         helper.assertTrue(menu.getSlot(WritingDeskMenu.COPY_RESULT).getItem().is(ModItems.PAGE.get()),
                 "Selecting the populated page must show a copy");
@@ -230,8 +272,8 @@ public final class WritingDeskGameTests {
         var player = helper.makeMockServerPlayerInLevel();
         player.moveTo(pos.getX() + 0.5, pos.getY() + 0.5, pos.getZ() + 0.5);
         WritingDeskMenu menu = new WritingDeskMenu(1, player.getInventory(), desk);
-        helper.assertFalse(menu.clickMenuButton(player, 101), "Out-of-range catalog index must be rejected");
+        helper.assertFalse(menu.clickMenuButton(player, WritingDeskMenu.CATALOG_BUTTON_BASE + 1), "Out-of-range catalog index must be rejected");
-        helper.assertTrue(menu.clickMenuButton(player, 100), "Known catalog symbol must be selectable");
+        helper.assertTrue(menu.clickMenuButton(player, WritingDeskMenu.CATALOG_BUTTON_BASE), "Known catalog symbol must be selectable");
         desk.setItem(WritingDeskBlockEntity.PAPER, new ItemStack(Items.PAPER));
         desk.setItem(WritingDeskBlockEntity.INK, new ItemStack(ModItems.INK_VIAL.get()));
         menu.broadcastChanges();
@@ -262,9 +304,9 @@ public final class WritingDeskGameTests {
                 "Full inventory must reject shift-click copy");
         helper.assertValueEqual(desk.getItem(WritingDeskBlockEntity.PAPER).getCount(), 1,
                 "Rejected copy must preserve paper");
-        helper.assertValueEqual(desk.inkRemaining(), 0, "Rejected copy must preserve ink meter");
+        helper.assertValueEqual(desk.inkRemaining(), 16, "Rejected copy must preserve the filled ink meter");
-        helper.assertTrue(desk.getItem(WritingDeskBlockEntity.INK).is(ModItems.INK_VIAL.get()),
+        helper.assertTrue(desk.getItem(WritingDeskBlockEntity.INK).isEmpty(),
-                "Rejected copy must preserve ink vial");
+                "The vial should already have refilled the empty meter");
         helper.succeed();
     }
 
@@ -340,9 +382,9 @@ public final class WritingDeskGameTests {
         var player = helper.makeMockServerPlayerInLevel();
         player.moveTo(pos.getX() + 0.5, pos.getY() + 0.5, pos.getZ() + 0.5);
         WritingDeskMenu menu = new WritingDeskMenu(1, player.getInventory(), desk);
-        helper.assertFalse(menu.clickMenuButton(player, 1000 + 2 * NotebookContents.MAX_PAGES),
+        helper.assertFalse(menu.clickMenuButton(player, WritingDeskMenu.ALL_PAGE_BUTTON_BASE + 2 * NotebookContents.MAX_PAGES),
                 "ALL view must reject empty cross-tab positions");
-        helper.assertTrue(menu.clickMenuButton(player, 1000 + NotebookContents.MAX_PAGES + 1),
+        helper.assertTrue(menu.clickMenuButton(player, WritingDeskMenu.ALL_PAGE_BUTTON_BASE + NotebookContents.MAX_PAGES + 1),
                 "ALL view must accept the populated second tab page");
         helper.assertTrue(ItemStack.matches(menu.getSlot(WritingDeskMenu.COPY_RESULT).getItem(), second),
                 "Copy preview must match the physical page selected from the other tab");
@@ -350,4 +392,231 @@ public final class WritingDeskGameTests {
                 "Selecting from ALL must not silently change the active tab");
         helper.succeed();
     }
+
+    @GameTest(template = "empty")
+    public static void tabGroupsCycleByFourAndProtectHiddenSlots(GameTestHelper helper) {
+        BlockPos pos = helper.absolutePos(new BlockPos(1, 1, 1));
+        helper.getLevel().setBlock(pos, ModBlocks.WRITING_DESK.get().defaultBlockState(), 3);
+        var desk = (WritingDeskBlockEntity) helper.getLevel().getBlockEntity(pos);
+        var player = helper.makeMockServerPlayerInLevel();
+        player.moveTo(pos.getX() + 0.5, pos.getY() + 0.5, pos.getZ() + 0.5);
+        var menu = new WritingDeskMenu(1, player.getInventory(), desk);
+        var otherViewer = new WritingDeskMenu(2, player.getInventory(), desk);
+        menu.clickMenuButton(player, WritingDeskMenu.PREVIOUS_TABS);
+        helper.assertValueEqual(menu.firstVisibleTab(), 0, "Previous must stop at tabs 1-4");
+        menu.clickMenuButton(player, WritingDeskMenu.NEXT_TABS);
+        helper.assertValueEqual(menu.firstVisibleTab(), 4, "Next must show tabs 5-8");
+        helper.assertValueEqual(otherViewer.firstVisibleTab(), 0, "Cycling must not move another viewer's slots");
+        helper.assertFalse(menu.getSlot(0).isActive(), "Earlier tab slots must be hidden");
+        helper.assertTrue(menu.getSlot(4).isActive(), "New group's slots must be interactive");
+        desk.setItem(0, new ItemStack(ModItems.NOTEBOOK.get()));
+        menu.clicked(0, 0, ClickType.PICKUP, player);
+        helper.assertTrue(menu.getCarried().isEmpty(), "Hidden slot clicks must not take items");
+        helper.assertTrue(menu.quickMoveStack(player, 0).isEmpty(), "Hidden shift-click must be rejected");
+        player.getInventory().setItem(9, new ItemStack(ModItems.NOTEBOOK.get()));
+        menu.quickMoveStack(player, WritingDeskMenu.COPY_RESULT + 1);
+        helper.assertTrue(desk.getItem(4).is(ModItems.NOTEBOOK.get()), "Shift-click must use the visible group");
+        for (int i = 0; i < 30; i++) menu.clickMenuButton(player, WritingDeskMenu.NEXT_TABS);
+        helper.assertValueEqual(menu.firstVisibleTab(), 84, "Last group must be tabs 85-88");
+        helper.assertTrue(menu.clickMenuButton(player, 87), "Tab 88 must be selectable without page-ID collisions");
+        helper.assertValueEqual(desk.activeCollection(), 87, "Tab 88 must become active");
+        helper.assertFalse(menu.clickMenuButton(player, 88), "Tab 89 must not exist");
+        desk.setItem(87, PageItem.createLinkPanelPage());
+        desk.setItem(WritingDeskBlockEntity.PAPER, new ItemStack(Items.PAPER));
+        desk.setItem(WritingDeskBlockEntity.INK, new ItemStack(ModItems.INK_VIAL.get()));
+        helper.assertTrue(menu.clickMenuButton(player, WritingDeskMenu.ALL_PAGE_BUTTON_BASE + 87 * NotebookContents.MAX_PAGES),
+                "ALL must select a physical page from tab 88");
+        helper.assertTrue(menu.quickMoveStack(player, WritingDeskMenu.COPY_RESULT).is(ModItems.PAGE.get()),
+                "Tab 88's page must be copyable");
+        menu.clickMenuButton(player, WritingDeskMenu.PREVIOUS_TABS);
+        helper.assertValueEqual(menu.firstVisibleTab(), 80, "Previous must move back four tabs");
+        helper.succeed();
+    }
+
+    @GameTest(template = "empty")
+    public static void oldDeskInventoryMigratesAndAll88TabsPersist(GameTestHelper helper) {
+        BlockPos pos = helper.absolutePos(new BlockPos(1, 1, 1));
+        var registries = helper.getLevel().registryAccess();
+        var oldItems = net.minecraft.core.NonNullList.withSize(8, ItemStack.EMPTY);
+        oldItems.set(0, new ItemStack(ModItems.NOTEBOOK.get()));
+        oldItems.set(3, PageItem.createLinkPanelPage());
+        oldItems.set(4, new ItemStack(ModItems.INK_VIAL.get(), 2));
+        oldItems.set(5, new ItemStack(Items.GLASS_BOTTLE, 3));
+        oldItems.set(6, new ItemStack(Items.PAPER, 12));
+        oldItems.set(7, PageItem.createLinkPanelPage());
+        var oldTag = new net.minecraft.nbt.CompoundTag();
+        net.minecraft.world.ContainerHelper.saveAllItems(oldTag, oldItems, registries);
+        oldTag.putInt("InkRemaining", 7);
+        oldTag.putInt("ActiveCollection", 3);
+        var desk = new WritingDeskBlockEntity(pos, ModBlocks.WRITING_DESK.get().defaultBlockState());
+        desk.loadWithComponents(oldTag, registries);
+        for (int i = 0; i < 4; i++) {
+            helper.assertTrue(ItemStack.matches(desk.getItem(i), oldItems.get(i)), "Original tab must survive migration");
+            helper.assertTrue(ItemStack.matches(desk.getItem(WritingDeskBlockEntity.INK + i), oldItems.get(4 + i)),
+                    "Original supplies and legacy output must survive migration");
+            helper.assertTrue(desk.getItem(4 + i).isEmpty(), "Supplies must not be duplicated into new tabs");
+        }
+        helper.assertValueEqual(desk.inkRemaining(), 7, "Migration must preserve ink meter");
+        helper.assertValueEqual(desk.activeCollection(), 3, "Migration must preserve active tab");
+        for (int i = 0; i < WritingDeskBlockEntity.COLLECTIONS; i++) desk.setItem(i, PageItem.createLinkPanelPage());
+        desk.setActiveCollection(87);
+        var restored = new WritingDeskBlockEntity(pos, ModBlocks.WRITING_DESK.get().defaultBlockState());
+        restored.loadWithComponents(desk.saveWithoutMetadata(registries), registries);
+        for (int i = 0; i < WritingDeskBlockEntity.COLLECTIONS; i++)
+            helper.assertTrue(restored.getItem(i).is(ModItems.PAGE.get()), "All 88 tab contents must survive save/load");
+        helper.assertValueEqual(restored.activeCollection(), 87, "Tab 88 selection must survive save/load");
+        helper.assertValueEqual(restored.getItem(WritingDeskBlockEntity.PAPER).getCount(), 12, "Reload must not repeat migration");
+        helper.succeed();
+    }
+
+    @GameTest(template = "empty")
+    public static void surfacePlacesCarriedPagesWithoutLossOrOverwrite(GameTestHelper helper) {
+        BlockPos pos = helper.absolutePos(new BlockPos(1, 1, 1));
+        helper.getLevel().setBlock(pos, ModBlocks.WRITING_DESK.get().defaultBlockState(), 3);
+        var desk = (WritingDeskBlockEntity) helper.getLevel().getBlockEntity(pos);
+        desk.setItem(87, new ItemStack(ModItems.NOTEBOOK.get()));
+        var player = helper.makeMockServerPlayerInLevel();
+        player.moveTo(pos.getX() + 0.5, pos.getY() + 0.5, pos.getZ() + 0.5);
+        var menu = new WritingDeskMenu(1, player.getInventory(), desk);
+        ItemStack held = PageItem.createLinkPanelPage().copyWithCount(3);
+        ItemStack expectedPage = held.copyWithCount(1);
+        player.getInventory().setItem(9, held);
+        menu.clicked(WritingDeskMenu.COPY_RESULT + 1, 0, ClickType.PICKUP, player);
+        int lastPosition = WritingDeskMenu.PLACE_PAGE_BUTTON_BASE + 87 * NotebookContents.MAX_PAGES + 26;
+        helper.assertTrue(menu.clickMenuButton(player, lastPosition), "Surface must place into final notebook position");
+        helper.assertValueEqual(menu.getCarried().getCount(), 2, "Placing must consume exactly one held page");
+        var pages = desk.getItem(87).get(ModDataComponents.NOTEBOOK_CONTENTS.get()).pages();
+        helper.assertValueEqual(pages.size(), 27, "Placement must preserve addressed position");
+        helper.assertTrue(pages.get(0).isEmpty() && pages.get(25).isEmpty(), "Placement must preserve preceding gaps");
+        helper.assertTrue(ItemStack.matches(pages.get(26), expectedPage), "Stored page must preserve components");
+        helper.assertFalse(menu.clickMenuButton(player, lastPosition), "Occupied position must not be overwritten");
+        helper.assertValueEqual(menu.getCarried().getCount(), 2, "Rejected placement must preserve cursor");
+        helper.assertFalse(menu.clickMenuButton(player, WritingDeskMenu.PLACE_PAGE_BUTTON_BASE + 88 * NotebookContents.MAX_PAGES),
+                "Out-of-range placement must be rejected");
+        helper.assertValueEqual(menu.pageCapacity(87), NotebookContents.MAX_PAGES, "Notebook tab must expose normal notebook capacity");
+        helper.assertValueEqual(menu.pageCapacity(0), 0, "Empty tab has no page storage");
+        helper.assertFalse(menu.clickMenuButton(player, WritingDeskMenu.PLACE_PAGE_BUTTON_BASE), "Empty tab must require a collection first");
+        desk.setItem(0, PageItem.createLinkPanelPage());
+        helper.assertValueEqual(menu.pageCapacity(0), 1, "Loose page tab must expose exactly one position");
+        helper.assertFalse(menu.clickMenuButton(player, WritingDeskMenu.PLACE_PAGE_BUTTON_BASE), "Loose page must not be replaced");
+        helper.assertFalse(menu.clickMenuButton(player, WritingDeskMenu.PLACE_PAGE_BUTTON_BASE + 1), "Loose page tab must not grow extra positions");
+        helper.assertValueEqual(menu.getCarried().getCount(), 2, "Rejected placements must preserve cursor");
+        helper.assertTrue(menu.clickMenuButton(player, lastPosition - 1), "A second empty notebook position must accept a page");
+        helper.assertTrue(menu.clickMenuButton(player, lastPosition - 2), "A third empty notebook position must accept the last page");
+        helper.assertTrue(menu.getCarried().isEmpty(), "Final placement must clear cursor");
+        menu.setCarried(new ItemStack(Items.DIAMOND));
+        helper.assertFalse(menu.clickMenuButton(player, lastPosition - 3), "Non-page items must be rejected");
+        helper.assertTrue(menu.getCarried().is(Items.DIAMOND), "Rejected item must remain held");
+        var restored = new WritingDeskBlockEntity(pos, ModBlocks.WRITING_DESK.get().defaultBlockState());
+        restored.loadWithComponents(desk.saveWithoutMetadata(helper.getLevel().registryAccess()), helper.getLevel().registryAccess());
+        helper.assertValueEqual(restored.getItem(87).get(ModDataComponents.NOTEBOOK_CONTENTS.get()).pageCount(), 3,
+                "Placed pages must persist in the notebook");
+        helper.succeed();
+    }
+
+    @GameTest(template = "empty")
+    public static void deskSurfaceDragMovesAndSwapsNotebookPages(GameTestHelper helper) {
+        BlockPos pos = helper.absolutePos(new BlockPos(1, 1, 1));
+        helper.getLevel().setBlock(pos, ModBlocks.WRITING_DESK.get().defaultBlockState(), 3);
+        var desk = (WritingDeskBlockEntity) helper.getLevel().getBlockEntity(pos);
+        ItemStack linkPanel = PageItem.createLinkPanelPage();
+        ItemStack terrain = PageItem.createSymbolPage(new SymbolReference(
+                ResourceLocation.parse("rivencraft:terrain/standard")));
+        ItemStack firstBook = new ItemStack(ModItems.NOTEBOOK.get());
+        firstBook.set(ModDataComponents.NOTEBOOK_CONTENTS.get(), new NotebookContents(List.of(linkPanel, terrain)));
+        desk.setItem(0, firstBook);
+        desk.setItem(1, new ItemStack(ModItems.NOTEBOOK.get()));
+        desk.setItem(2, PageItem.createLinkPanelPage());
+        var player = helper.makeMockServerPlayerInLevel();
+        player.moveTo(pos.getX() + 0.5, pos.getY() + 0.5, pos.getZ() + 0.5);
+        var menu = new WritingDeskMenu(1, player.getInventory(), desk);
+        int moveToEmpty = WritingDeskMenu.movePageButtonId(0, 0, 0, 26);
+        helper.assertTrue(menu.clickMenuButton(player, moveToEmpty), "Drag must move to a distant empty notebook position");
+        var pages = desk.getItem(0).get(ModDataComponents.NOTEBOOK_CONTENTS.get()).pages();
+        helper.assertTrue(pages.get(0).isEmpty(), "Moving must clear the source position");
+        helper.assertTrue(ItemStack.matches(pages.get(26), linkPanel), "Moving must preserve page components");
+        helper.assertValueEqual(desk.getItem(0).get(ModDataComponents.NOTEBOOK_CONTENTS.get()).pageCount(), 2,
+                "Moving must preserve total page count");
+        helper.assertTrue(menu.clickMenuButton(player, WritingDeskMenu.movePageButtonId(0, 26, 0, 1)),
+                "Drag onto an occupied position must swap pages");
+        pages = desk.getItem(0).get(ModDataComponents.NOTEBOOK_CONTENTS.get()).pages();
+        helper.assertTrue(ItemStack.matches(pages.get(1), linkPanel) && ItemStack.matches(pages.get(26), terrain),
+                "Swap must preserve both pages");
+        helper.assertTrue(menu.clickMenuButton(player, WritingDeskMenu.movePageButtonId(0, 1, 1, 5)),
+                "Drag into another notebook must work");
+        var otherPages = desk.getItem(1).get(ModDataComponents.NOTEBOOK_CONTENTS.get()).pages();
+        helper.assertTrue(ItemStack.matches(otherPages.get(5), linkPanel)
+                && desk.getItem(0).get(ModDataComponents.NOTEBOOK_CONTENTS.get()).pages().get(1).isEmpty(),
+                "Cross notebook move must have one destination and no old source");
+        helper.assertFalse(menu.clickMenuButton(player, WritingDeskMenu.movePageButtonId(0, 1, 1, 6)),
+                "Dragging an empty source must be rejected");
+        helper.assertTrue(menu.clickMenuButton(player, WritingDeskMenu.movePageButtonId(2, 0, 1, 6)),
+                "A loose page should move into a notebook position");
+        helper.assertTrue(desk.getItem(2).isEmpty()
+                && desk.getItem(1).get(ModDataComponents.NOTEBOOK_CONTENTS.get()).pages().get(6).is(ModItems.PAGE.get()),
+                "Moving a loose page must empty its tab without losing the item");
+        helper.assertFalse(menu.clickMenuButton(player, WritingDeskMenu.movePageButtonId(1, 5, 1, 5)),
+                "A no-op drag must be rejected");
+        menu.setCarried(new ItemStack(Items.DIAMOND));
+        helper.assertFalse(menu.clickMenuButton(player, WritingDeskMenu.movePageButtonId(1, 5, 1, 6)),
+                "Held inventory items must not be moved by a panel drag");
+        helper.assertTrue(ItemStack.matches(desk.getItem(1).get(ModDataComponents.NOTEBOOK_CONTENTS.get()).pages().get(5), linkPanel),
+                "Rejected drags must leave notebook data intact");
+        helper.succeed();
+    }
+
+    @GameTest(template = "empty")
+    public static void deskSurfaceDragExtractsPagesToInventoryAndTabs(GameTestHelper helper) {
+        BlockPos pos = helper.absolutePos(new BlockPos(1, 1, 1));
+        helper.getLevel().setBlock(pos, ModBlocks.WRITING_DESK.get().defaultBlockState(), 3);
+        var desk = (WritingDeskBlockEntity) helper.getLevel().getBlockEntity(pos);
+        ItemStack page = PageItem.createLinkPanelPage();
+        ItemStack source = new ItemStack(ModItems.NOTEBOOK.get());
+        source.set(ModDataComponents.NOTEBOOK_CONTENTS.get(),
+                new NotebookContents(List.of(page, page, page, page, page, page)));
+        desk.setItem(0, source);
+        ItemStack otherBook = new ItemStack(ModItems.NOTEBOOK.get());
+        ItemStack terrain = PageItem.createSymbolPage(new SymbolReference(
+                ResourceLocation.parse("rivencraft:terrain/standard")));
+        otherBook.set(ModDataComponents.NOTEBOOK_CONTENTS.get(), new NotebookContents(List.of(terrain)));
+        desk.setItem(2, otherBook);
+        var player = helper.makeMockServerPlayerInLevel();
+        player.moveTo(pos.getX() + 0.5, pos.getY() + 0.5, pos.getZ() + 0.5);
+        player.getInventory().setItem(10, page.copyWithCount(2));
+        var menu = new WritingDeskMenu(1, player.getInventory(), desk);
+        int inventoryStart = WritingDeskMenu.COPY_RESULT + 1;
+
+        helper.assertTrue(menu.clickMenuButton(player, WritingDeskMenu.extractPageButtonId(0, 0, -1)),
+                "Dropping away from a slot must return the page to the cursor");
+        helper.assertTrue(ItemStack.matches(menu.getCarried(), page), "Cursor must hold the original page item");
+        helper.assertFalse(menu.clickMenuButton(player, WritingDeskMenu.extractPageButtonId(0, 1, inventoryStart)),
+                "Extraction must not replace an occupied cursor");
+        menu.setCarried(ItemStack.EMPTY);
+        helper.assertTrue(menu.clickMenuButton(player, WritingDeskMenu.extractPageButtonId(0, 1, inventoryStart)),
+                "Dropping on player inventory must transfer a page");
+        helper.assertTrue(ItemStack.matches(player.getInventory().getItem(9), page),
+                "Transferred page must retain its components");
+        helper.assertTrue(menu.clickMenuButton(player, WritingDeskMenu.extractPageButtonId(0, 2, 1)),
+                "Dropping on an empty tab must store a loose page");
+        helper.assertTrue(ItemStack.matches(desk.getItem(1), page), "Tab must hold the extracted page");
+        helper.assertTrue(menu.clickMenuButton(player, WritingDeskMenu.extractPageButtonId(0, 3, 2)),
+                "Dropping on a notebook tab must insert the page");
+        var otherPages = desk.getItem(2).get(ModDataComponents.NOTEBOOK_CONTENTS.get()).pages();
+        helper.assertTrue(ItemStack.matches(otherPages.get(0), terrain)
+                && ItemStack.matches(otherPages.get(1), page), "Notebook drop must preserve existing pages");
+        helper.assertTrue(menu.clickMenuButton(player, WritingDeskMenu.extractPageButtonId(0, 4, inventoryStart + 1)),
+                "Dropping on a matching inventory stack must merge one page");
+        helper.assertValueEqual(player.getInventory().getItem(10).getCount(), 3, "Merge must add exactly one page");
+        helper.assertFalse(menu.clickMenuButton(player, WritingDeskMenu.extractPageButtonId(0, 5, 1)),
+                "Occupied loose-page tabs must reject a drop");
+        helper.assertFalse(menu.clickMenuButton(player, WritingDeskMenu.extractPageButtonId(0, 5, WritingDeskBlockEntity.INK)),
+                "Ink slot must not accept an extracted page");
+        helper.assertValueEqual(desk.getItem(0).get(ModDataComponents.NOTEBOOK_CONTENTS.get()).pageCount(), 1,
+                "Rejected drops must leave the remaining source page in the notebook");
+        helper.assertTrue(menu.clickMenuButton(player, WritingDeskMenu.extractPageButtonId(1, 0, -1)),
+                "A loose page shown on the panel must be draggable back to the cursor");
+        helper.assertTrue(desk.getItem(1).isEmpty() && ItemStack.matches(menu.getCarried(), page),
+                "Extracting a loose page must empty its tab and return the same item");
+        helper.succeed();
+    }
 }

src/main/java/net/dnorberg/rivencraft/menu/WritingDeskMenu.java

@@ -29,13 +29,25 @@ import net.minecraft.world.item.Items;
 
 public final class WritingDeskMenu extends AbstractContainerMenu {
     public static final int COPY_RESULT = WritingDeskBlockEntity.SIZE;
+    public static final int VISIBLE_TABS = 4;
+    public static final int PREVIOUS_TABS = 90;
+    public static final int NEXT_TABS = 91;
+    public static final int PAGE_BUTTON_BASE = 128;
+    public static final int CATALOG_BUTTON_BASE = 512;
+    public static final int ALL_PAGE_BUTTON_BASE = 32768;
+    public static final int PLACE_PAGE_BUTTON_BASE = 65536;
+    private static final int PAGE_ADDRESS_COUNT = WritingDeskBlockEntity.COLLECTIONS * NotebookContents.MAX_PAGES;
+    public static final int MOVE_PAGE_BUTTON_BASE = PLACE_PAGE_BUTTON_BASE + PAGE_ADDRESS_COUNT;
     private static final int PLAYER_START = COPY_RESULT + 1;
+    private static final int EXTRACT_TARGET_COUNT = PLAYER_START + 36 + 1;
+    public static final int EXTRACT_PAGE_BUTTON_BASE = MOVE_PAGE_BUTTON_BASE + PAGE_ADDRESS_COUNT * PAGE_ADDRESS_COUNT;
     private final Container desk;
     private final WritingDeskBlockEntity blockEntity;
     private final SimpleContainer result = new SimpleContainer(1);
     private final boolean clientSide;
     private int syncedActiveCollection;
     private int syncedInkRemaining;
+    private int firstVisibleTab;
     private int selectedPage;
     private int selectedCollection = -1;
     private ResourceLocation selectedSymbol;
@@ -55,6 +67,11 @@ public final class WritingDeskMenu extends AbstractContainerMenu {
         this.clientSide = inventory.player.level().isClientSide;
         this.serverViewer = inventory.player instanceof ServerPlayer serverPlayer ? serverPlayer : null;
         if (blockEntity != null && !clientSide) catalog = WritingDeskCatalog.available(blockEntity);
+        firstVisibleTab = blockEntity == null ? 0 : blockEntity.activeCollection() / VISIBLE_TABS * VISIBLE_TABS;
+        addDataSlot(new DataSlot() {
+            @Override public int get() { return firstVisibleTab; }
+            @Override public void set(int value) { firstVisibleTab = value; }
+        });
         addDataSlot(new DataSlot() {
             @Override public int get() { return WritingDeskMenu.this.blockEntity == null
                     ? syncedActiveCollection : WritingDeskMenu.this.blockEntity.activeCollection(); }
@@ -66,53 +83,94 @@ public final class WritingDeskMenu extends AbstractContainerMenu {
             @Override public void set(int value) { syncedInkRemaining = value; }
         });
         for (int i = 0; i < WritingDeskBlockEntity.COLLECTIONS; i++) {
-            addSlot(new DeskSlot(desk, i, 36, 20 + i * 37, 1));
+            addSlot(new DeskSlot(desk, i, 37, 34 + (i % VISIBLE_TABS) * 37, 1));
         }
-        addSlot(new DeskSlot(desk, WritingDeskBlockEntity.INK, 370, 9, 16));
+        addSlot(new DeskSlot(desk, WritingDeskBlockEntity.INK, 385, 28, 16));
-        addSlot(new DeskSlot(desk, WritingDeskBlockEntity.RETURN, 370, 57, 64));
+        addSlot(new DeskSlot(desk, WritingDeskBlockEntity.RETURN, 385, 80, 64));
-        addSlot(new DeskSlot(desk, WritingDeskBlockEntity.PAPER, 228, 9, 64));
+        addSlot(new DeskSlot(desk, WritingDeskBlockEntity.PAPER, 241, 28, 64));
         addSlot(new DeskSlot(desk, WritingDeskBlockEntity.LEGACY_OUTPUT, -1000, -1000, 64));
-        addSlot(new CopySlot(result, 0, 228, 57));
+        addSlot(new CopySlot(result, 0, 241, 80));
         for (int row = 0; row < 3; row++) {
             for (int column = 0; column < 9; column++) {
-                addSlot(new Slot(inventory, column + row * 9 + 9, 224 + column * 18, 79 + row * 18));
+                addSlot(new Slot(inventory, column + row * 9 + 9, 241 + column * 18, 104 + row * 18));
             }
         }
         for (int column = 0; column < 9; column++) {
-            addSlot(new Slot(inventory, column, 224 + column * 18, 137));
+            addSlot(new Slot(inventory, column, 241 + column * 18, 162));
         }
     }
 
     public int activeCollection() { return syncedActiveCollection; }
+    public int firstVisibleTab() { return firstVisibleTab; }
     public int inkRemaining() { return syncedInkRemaining; }
+    public int pageCapacity(int collectionIndex) {
+        if (collectionIndex < 0 || collectionIndex >= WritingDeskBlockEntity.COLLECTIONS) return 0;
+        ItemStack collection = desk.getItem(collectionIndex);
+        return collection.is(ModItems.NOTEBOOK.get()) ? NotebookContents.MAX_PAGES
+                : collection.is(ModItems.PAGE.get()) ? 1 : 0;
+    }
     public List<SymbolDisplayMetadata> catalog() { return catalog; }
     public void setCatalog(List<SymbolDisplayMetadata> symbols) { catalog = List.copyOf(symbols); }
 
+    public static int movePageButtonId(int sourceCollection, int sourcePage, int targetCollection, int targetPage) {
+        int source = sourceCollection * NotebookContents.MAX_PAGES + sourcePage;
+        int target = targetCollection * NotebookContents.MAX_PAGES + targetPage;
+        return MOVE_PAGE_BUTTON_BASE + source * PAGE_ADDRESS_COUNT + target;
+    }
+
+    /** targetSlot is -1 for the cursor, otherwise a visible player or desk-tab slot. */
+    public static int extractPageButtonId(int sourceCollection, int sourcePage, int targetSlot) {
+        int source = sourceCollection * NotebookContents.MAX_PAGES + sourcePage;
+        return EXTRACT_PAGE_BUTTON_BASE + source * EXTRACT_TARGET_COUNT + targetSlot + 1;
+    }
+
     @Override public boolean clickMenuButton(Player player, int id) {
         if (blockEntity == null || !stillValid(player)) return false;
-        if (id >= 0 && id < WritingDeskBlockEntity.COLLECTIONS) {
+        if (id == PREVIOUS_TABS || id == NEXT_TABS) {
+            firstVisibleTab = Math.clamp(firstVisibleTab + (id == NEXT_TABS ? VISIBLE_TABS : -VISIBLE_TABS),
+                    0, WritingDeskBlockEntity.COLLECTIONS - VISIBLE_TABS);
+            return true;
+        } else if (id >= 0 && id < WritingDeskBlockEntity.COLLECTIONS) {
+            if (id < firstVisibleTab || id >= firstVisibleTab + VISIBLE_TABS) return false;
             blockEntity.setActiveCollection(id);
             selectedPage = 0;
             selectedCollection = -1;
             selectedSymbol = null;
-        } else if (id >= 16 && id < 16 + NotebookContents.MAX_PAGES) {
+        } else if (id >= EXTRACT_PAGE_BUTTON_BASE
-            selectedPage = id - 16;
+                && id < EXTRACT_PAGE_BUTTON_BASE + PAGE_ADDRESS_COUNT * EXTRACT_TARGET_COUNT) {
+            int offset = id - EXTRACT_PAGE_BUTTON_BASE;
+            int source = offset / EXTRACT_TARGET_COUNT;
+            int targetSlot = offset % EXTRACT_TARGET_COUNT - 1;
+            if (!extractPage(source / NotebookContents.MAX_PAGES, source % NotebookContents.MAX_PAGES,
+                    targetSlot)) return false;
+        } else if (id >= MOVE_PAGE_BUTTON_BASE && id < MOVE_PAGE_BUTTON_BASE + PAGE_ADDRESS_COUNT * PAGE_ADDRESS_COUNT) {
+            int offset = id - MOVE_PAGE_BUTTON_BASE;
+            int source = offset / PAGE_ADDRESS_COUNT;
+            int target = offset % PAGE_ADDRESS_COUNT;
+            if (!movePage(source / NotebookContents.MAX_PAGES, source % NotebookContents.MAX_PAGES,
+                    target / NotebookContents.MAX_PAGES, target % NotebookContents.MAX_PAGES)) return false;
+        } else if (id >= PLACE_PAGE_BUTTON_BASE
+                && id < PLACE_PAGE_BUTTON_BASE + WritingDeskBlockEntity.COLLECTIONS * NotebookContents.MAX_PAGES) {
+            int offset = id - PLACE_PAGE_BUTTON_BASE;
+            if (!placeCarriedPage(offset / NotebookContents.MAX_PAGES, offset % NotebookContents.MAX_PAGES)) return false;
+        } else if (id >= PAGE_BUTTON_BASE && id < PAGE_BUTTON_BASE + NotebookContents.MAX_PAGES) {
+            selectedPage = id - PAGE_BUTTON_BASE;
             selectedCollection = -1;
             selectedSymbol = null;
-        } else if (id >= 1000 && id < 1000 + WritingDeskBlockEntity.COLLECTIONS * NotebookContents.MAX_PAGES) {
+        } else if (id >= ALL_PAGE_BUTTON_BASE && id < ALL_PAGE_BUTTON_BASE + WritingDeskBlockEntity.COLLECTIONS * NotebookContents.MAX_PAGES) {
-            int offset = id - 1000;
+            int offset = id - ALL_PAGE_BUTTON_BASE;
             int collection = offset / NotebookContents.MAX_PAGES;
             int page = offset % NotebookContents.MAX_PAGES;
             if (pageAt(collection, page).isEmpty()) return false;
             selectedCollection = collection;
             selectedPage = page;
             selectedSymbol = null;
-        } else if (id >= 100 && id < 100 + catalog.size()) {
+        } else if (id >= CATALOG_BUTTON_BASE && id < CATALOG_BUTTON_BASE + catalog.size()) {
             if (!catalog.equals(WritingDeskCatalog.available(blockEntity))) {
                 refreshCatalog();
                 return false;
             }
-            ResourceLocation requested = catalog.get(id - 100).id();
+            ResourceLocation requested = catalog.get(id - CATALOG_BUTTON_BASE).id();
             if (!WritingDeskCatalog.available(blockEntity).stream().anyMatch(entry -> entry.id().equals(requested))) {
                 return false;
             }
@@ -122,6 +180,129 @@ public final class WritingDeskMenu extends AbstractContainerMenu {
         return true;
     }
 
+    private boolean placeCarriedPage(int collectionIndex, int pageIndex) {
+        // Resolve the actual storage position on the server, never a filtered list index.
+        ItemStack carried = getCarried();
+        if (clientSide || !carried.is(ModItems.PAGE.get())) return false;
+        ItemStack collection = desk.getItem(collectionIndex);
+        if (collection.is(ModItems.NOTEBOOK.get())) {
+            var pages = new java.util.ArrayList<>(collection.getOrDefault(
+                    ModDataComponents.NOTEBOOK_CONTENTS.get(), NotebookContents.EMPTY).pages());
+            while (pages.size() <= pageIndex) pages.add(ItemStack.EMPTY);
+            if (!pages.get(pageIndex).isEmpty()) return false;
+            pages.set(pageIndex, carried.copyWithCount(1));
+            ItemStack updated = collection.copy();
+            updated.set(ModDataComponents.NOTEBOOK_CONTENTS.get(), new NotebookContents(pages));
+            desk.setItem(collectionIndex, updated);
+        } else return false;
+        carried.shrink(1);
+        setCarried(carried.isEmpty() ? ItemStack.EMPTY : carried);
+        selectedCollection = collectionIndex;
+        selectedPage = pageIndex;
+        selectedSymbol = null;
+        refreshCatalog();
+        broadcastChanges();
+        return true;
+    }
+
+    private boolean movePage(int sourceCollection, int sourcePage, int targetCollection, int targetPage) {
+        if (!getCarried().isEmpty() || sourceCollection == targetCollection && sourcePage == targetPage) return false;
+        ItemStack sourceBook = desk.getItem(sourceCollection);
+        ItemStack targetBook = desk.getItem(targetCollection);
+        boolean sourceNotebook = sourceBook.is(ModItems.NOTEBOOK.get());
+        boolean targetNotebook = targetBook.is(ModItems.NOTEBOOK.get());
+        if ((!sourceNotebook && (!sourceBook.is(ModItems.PAGE.get()) || sourcePage != 0))
+                || (!targetNotebook && (!targetBook.is(ModItems.PAGE.get()) || targetPage != 0))) return false;
+        var sourcePages = sourceNotebook ? new java.util.ArrayList<>(sourceBook.getOrDefault(
+                ModDataComponents.NOTEBOOK_CONTENTS.get(), NotebookContents.EMPTY).pages()) : null;
+        if (sourceNotebook && (sourcePage >= sourcePages.size() || sourcePages.get(sourcePage).isEmpty())) return false;
+        ItemStack moving = sourceNotebook ? sourcePages.get(sourcePage) : sourceBook;
+        if (moving.getCount() != 1) return false;
+        if (!targetNotebook && targetBook.getCount() != 1) return false;
+        var targetPages = targetNotebook ? sourceCollection == targetCollection ? sourcePages
+                : new java.util.ArrayList<>(targetBook.getOrDefault(
+                        ModDataComponents.NOTEBOOK_CONTENTS.get(), NotebookContents.EMPTY).pages()) : null;
+        if (targetNotebook) while (targetPages.size() <= targetPage) targetPages.add(ItemStack.EMPTY);
+        ItemStack displaced = targetNotebook ? targetPages.get(targetPage) : targetBook;
+        if (targetNotebook) targetPages.set(targetPage, moving);
+        if (sourceNotebook) {
+            sourcePages.set(sourcePage, displaced);
+            ItemStack updatedSource = sourceBook.copy();
+            updatedSource.set(ModDataComponents.NOTEBOOK_CONTENTS.get(), new NotebookContents(sourcePages));
+            desk.setItem(sourceCollection, updatedSource);
+        } else desk.setItem(sourceCollection, displaced.isEmpty() ? ItemStack.EMPTY : displaced.copyWithCount(1));
+        if (targetNotebook && sourceCollection != targetCollection) {
+            ItemStack updatedTarget = targetBook.copy();
+            updatedTarget.set(ModDataComponents.NOTEBOOK_CONTENTS.get(), new NotebookContents(targetPages));
+            desk.setItem(targetCollection, updatedTarget);
+        } else if (!targetNotebook) desk.setItem(targetCollection, moving.copyWithCount(1));
+        selectedCollection = targetCollection;
+        selectedPage = targetPage;
+        selectedSymbol = null;
+        refreshCatalog();
+        broadcastChanges();
+        return true;
+    }
+
+    private boolean extractPage(int sourceCollection, int sourcePage, int targetSlot) {
+        if (!getCarried().isEmpty() || targetSlot < -1 || targetSlot >= slots.size()) return false;
+        ItemStack sourceBook = desk.getItem(sourceCollection);
+        boolean sourceNotebook = sourceBook.is(ModItems.NOTEBOOK.get());
+        if (!sourceNotebook && (!sourceBook.is(ModItems.PAGE.get()) || sourcePage != 0)) return false;
+        var sourcePages = sourceNotebook ? new java.util.ArrayList<>(sourceBook.getOrDefault(
+                ModDataComponents.NOTEBOOK_CONTENTS.get(), NotebookContents.EMPTY).pages()) : null;
+        if (sourceNotebook && (sourcePage >= sourcePages.size() || sourcePages.get(sourcePage).isEmpty())) return false;
+        ItemStack moving = sourceNotebook ? sourcePages.get(sourcePage).copyWithCount(1) : sourceBook.copyWithCount(1);
+        if (!sourceNotebook && sourceBook.getCount() != 1) return false;
+
+        if (targetSlot == -1) {
+            setCarried(moving);
+        } else {
+            if (targetSlot >= WritingDeskBlockEntity.COLLECTIONS && targetSlot < PLAYER_START) return false;
+            Slot target = slots.get(targetSlot);
+            if (!target.isActive() || !target.mayPlace(moving)) return false;
+            ItemStack current = target.getItem();
+            if (targetSlot < WritingDeskBlockEntity.COLLECTIONS && current.is(ModItems.NOTEBOOK.get())) {
+                var targetPages = targetSlot == sourceCollection ? sourcePages
+                        : new java.util.ArrayList<>(current.getOrDefault(
+                                ModDataComponents.NOTEBOOK_CONTENTS.get(), NotebookContents.EMPTY).pages());
+                int position = -1;
+                for (int i = 0; i < NotebookContents.MAX_PAGES; i++) {
+                    if (i >= targetPages.size() || targetPages.get(i).isEmpty()) {
+                        position = i;
+                        break;
+                    }
+                }
+                if (position < 0) return false;
+                while (targetPages.size() <= position) targetPages.add(ItemStack.EMPTY);
+                targetPages.set(position, moving);
+                if (targetSlot != sourceCollection) {
+                    ItemStack updatedTarget = current.copy();
+                    updatedTarget.set(ModDataComponents.NOTEBOOK_CONTENTS.get(), new NotebookContents(targetPages));
+                    target.setByPlayer(updatedTarget);
+                }
+            } else if (current.isEmpty()) {
+                target.setByPlayer(moving);
+            } else if (targetSlot >= PLAYER_START && ItemStack.isSameItemSameComponents(current, moving)
+                    && current.getCount() < target.getMaxStackSize(moving)) {
+                target.setByPlayer(current.copyWithCount(current.getCount() + 1));
+            } else return false;
+        }
+
+        if (sourceNotebook) {
+            sourcePages.set(sourcePage, ItemStack.EMPTY);
+            ItemStack updatedSource = sourceBook.copy();
+            updatedSource.set(ModDataComponents.NOTEBOOK_CONTENTS.get(), new NotebookContents(sourcePages));
+            desk.setItem(sourceCollection, updatedSource);
+        } else desk.setItem(sourceCollection, ItemStack.EMPTY);
+        selectedCollection = sourceCollection;
+        selectedPage = sourcePage;
+        selectedSymbol = null;
+        refreshCatalog();
+        broadcastChanges();
+        return true;
+    }
+
     @Override public boolean stillValid(Player player) {
         return blockEntity != null && blockEntity.stillValid(player);
     }
@@ -141,6 +322,7 @@ public final class WritingDeskMenu extends AbstractContainerMenu {
             return copy;
         }
         Slot slot = slots.get(index);
+        if (!slot.isActive()) return ItemStack.EMPTY;
         if (!slot.hasItem()) return ItemStack.EMPTY;
         ItemStack moving = slot.getItem();
         ItemStack original = moving.copy();
@@ -155,12 +337,13 @@ public final class WritingDeskMenu extends AbstractContainerMenu {
     }
 
     private boolean moveIntoDesk(ItemStack moving) {
-        if (moving.is(ModItems.INK_VIAL.get())) return moveItemStackTo(moving, 4, 5, false);
+        if (moving.is(ModItems.INK_VIAL.get())) return moveItemStackTo(moving,
-        if (moving.is(ModItems.NOTEBOOK.get())) return moveItemStackTo(moving, 0, 4, false);
+                WritingDeskBlockEntity.INK, WritingDeskBlockEntity.INK + 1, false);
+        if (moving.is(ModItems.NOTEBOOK.get())) return moveItemStackTo(moving, firstVisibleTab, firstVisibleTab + VISIBLE_TABS, false);
         if (moving.is(Items.PAPER))
             return moveItemStackTo(moving, WritingDeskBlockEntity.PAPER,
                     WritingDeskBlockEntity.PAPER + 1, false);
-        if (moving.is(ModItems.PAGE.get())) return moveItemStackTo(moving, 0, 4, false);
+        if (moving.is(ModItems.PAGE.get())) return moveItemStackTo(moving, firstVisibleTab, firstVisibleTab + VISIBLE_TABS, false);
         return false;
     }
 
@@ -230,6 +413,7 @@ public final class WritingDeskMenu extends AbstractContainerMenu {
         }
         refreshCatalog();
         refreshOutput();
+        if (slotId >= 0 && slotId < slots.size() && !slots.get(slotId).isActive()) return;
         super.clicked(slotId, button, clickType, player);
     }
 
@@ -245,13 +429,19 @@ public final class WritingDeskMenu extends AbstractContainerMenu {
         }
     }
 
-    private static final class DeskSlot extends Slot {
+    private final class DeskSlot extends Slot {
         private final int limit;
         private DeskSlot(Container container, int index, int x, int y, int limit) {
             super(container, index, x, y);
             this.limit = limit;
         }
-        @Override public boolean mayPlace(ItemStack stack) { return container.canPlaceItem(getContainerSlot(), stack); }
+        @Override public boolean isActive() {
+            int slot = getContainerSlot();
+            return slot >= WritingDeskBlockEntity.COLLECTIONS
+                    || slot >= firstVisibleTab && slot < firstVisibleTab + VISIBLE_TABS;
+        }
+        @Override public boolean mayPickup(Player player) { return isActive(); }
+        @Override public boolean mayPlace(ItemStack stack) { return isActive() && container.canPlaceItem(getContainerSlot(), stack); }
         @Override public int getMaxStackSize() { return limit; }
     }
 }

src/main/java/net/dnorberg/rivencraft/network/ModNetworking.java

@@ -49,7 +49,7 @@ public final class ModNetworking {
     }
 
     public static void register(RegisterPayloadHandlersEvent event) {
-        PayloadRegistrar registrar = event.registrar("10");
+        PayloadRegistrar registrar = event.registrar("11");
         registrar.playToServer(RequestDescriptiveBookScreenPayload.TYPE, RequestDescriptiveBookScreenPayload.STREAM_CODEC,
                 ModNetworking::requestDescriptiveBookScreen);
         registrar.playToClient(OpenDescriptiveBookScreenPayload.TYPE, OpenDescriptiveBookScreenPayload.STREAM_CODEC,