Revert "fix glyph-overhang artifacts in partial row repaint"

This reverts commit 57103bb98b.

.gitignore

@@ -13,3 +13,4 @@ devenv.local.yaml
 build
 build
 .gradle
+bin

.ignore

@@ -0,0 +1,3 @@
+.gradle
+result
+bin

README.md

@@ -106,7 +106,6 @@ navigate_up = "ALT+K"
 navigate_right = "ALT+L"
 toggle_floating = "ALT+F"
 new_pane = "ALT+N"
-next_floating = "ALT+F12"
 close_pane = "ALT+X"
 new_tab = "ALT+A"
 previous_tab = "ALT+SHIFT+H"
@@ -121,7 +120,6 @@ open_scrollback = "ALT+S"
 - `Alt+n`: new pane — a floating pane when floating panes are shown, otherwise a new tiled
   pane (tiled panes are split equally across the width)
 - `Alt+f`: show or hide all floating panes
-- `Alt+F12`: cycle floating panes
 - `Alt+x`: close the active pane; closing a tab's last pane closes the tab, and closing the
   last pane of the last tab quits
 - `Alt+a`: new tab

config.example.toml

@@ -25,8 +25,7 @@ navigate_down = "ALT+J"
 navigate_up = "ALT+K"
 navigate_right = "ALT+L"
 toggle_floating = "ALT+F"
-new_floating = "ALT+SHIFT+F"
+new_pane = "ALT+N"
-next_floating = "ALT+F12"
 close_pane = "ALT+X"
 open_font_selector = "ALT+T"
 open_scrollback = "ALT+S"

flake.lock

@@ -70,11 +70,11 @@
         "nixpkgs": "nixpkgs"
       },
       "locked": {
-        "lastModified": 1780079529,
+        "lastModified": 1780256181,
-        "narHash": "sha256-AxlGTL8c5xSLcQHvWlm994IdOqxsN8iKrA02Cpv7vso=",
+        "narHash": "sha256-/saXdnYMbAMfP7u6USSqtNkBIgqZhU+CPr3F8tUQhHU=",
         "ref": "refs/heads/main",
-        "rev": "68121d50b52fb56038871c97c97e7a12ffe987c2",
+        "rev": "db5ee5d20daf8855de3a3b2fa9349eced70946f0",
-        "revCount": 20,
+        "revCount": 21,
         "type": "git",
         "url": "https://gitea.gregorlohaus.com/gregor/jlibghostty.git"
       },

src/main/java/com/gregor/jprototerm/AppConfig.java

@@ -37,7 +37,6 @@ public record AppConfig(
             "navigate_right",
             "toggle_floating",
             "new_pane",
-            "next_floating",
             "close_pane",
             "new_tab",
             "previous_tab",
@@ -96,7 +95,6 @@ public record AppConfig(
                         Map.entry("navigate_right", KeyBinding.parse("ALT+L")),
                         Map.entry("toggle_floating", KeyBinding.parse("ALT+F")),
                         Map.entry("new_pane", KeyBinding.parse("ALT+N")),
-                        Map.entry("next_floating", KeyBinding.parse("ALT+F12")),
                         Map.entry("close_pane", KeyBinding.parse("ALT+X")),
                         Map.entry("new_tab", KeyBinding.parse("ALT+A")),
                         Map.entry("previous_tab", KeyBinding.parse("ALT+SHIFT+H")),

src/main/java/com/gregor/jprototerm/Compositor.java

@@ -0,0 +1,442 @@
+package com.gregor.jprototerm;
+
+import dev.jlibghostty.KeyModifiers;
+import dev.jlibghostty.MouseButton;
+import dev.jlibghostty.MouseEncoderSize;
+import dev.jlibghostty.MouseInput;
+import javafx.geometry.Pos;
+import javafx.scene.Parent;
+import javafx.scene.control.Label;
+import javafx.scene.input.InputEvent;
+import javafx.scene.input.MouseEvent;
+import javafx.scene.input.ScrollEvent;
+import javafx.scene.input.ScrollEvent.VerticalTextScrollUnits;
+import javafx.scene.layout.Background;
+import javafx.scene.layout.BackgroundFill;
+import javafx.scene.layout.CornerRadii;
+import javafx.scene.layout.HBox;
+import javafx.scene.layout.Pane;
+import javafx.scene.paint.Color;
+
+import java.util.ArrayList;
+import java.util.HashMap;
+import java.util.HashSet;
+import java.util.List;
+import java.util.Map;
+import java.util.Set;
+
+/**
+ * Owns the window's tabs and exposes the terminal surface as a JavaFX scene graph. Each
+ * terminal pane is mounted as its own node, so JavaFX child order handles stacking and clipping
+ * between panes. The pane model still owns terminals, ptys, cell geometry, and snapshots; this
+ * class handles tab/pane lifecycle, layout, focus, mouse routing, and frame scheduling.
+ */
+public final class Compositor {
+    private static final Color GAP_BACKGROUND = Color.rgb(16, 16, 18);
+    private static final Color TAB_TEXT = Color.rgb(225, 229, 235);
+    private static final Color TAB_INACTIVE_TEXT = Color.rgb(128, 136, 148);
+    private static final Color TAB_ACTIVE_BACKGROUND = Color.rgb(45, 55, 72);
+    private static final Color TAB_INACTIVE_BACKGROUND = Color.rgb(22, 24, 28);
+    private static final double TAB_BAR_HEIGHT = 22.0;
+
+    private final Pane root = new Pane();
+    private final Pane paneLayer = new Pane();
+    private final HBox tabBar = new HBox(1.0);
+    private final AppConfig config;
+    private final TerminalMetrics metrics;
+    private final List<Tab> tabs = new ArrayList<>();
+    private final Map<TerminalPane, TerminalPaneNode> nodes = new HashMap<>();
+    private int currentTabIndex;
+    private boolean sceneDirty = true;
+    private double lastWidth = -1.0;
+    private double lastHeight = -1.0;
+    private long lastContentVersion = Long.MIN_VALUE;
+    private boolean mouseButtonPressed;
+    private MouseButton pressedButton = MouseButton.UNKNOWN;
+
+    public Compositor(AppConfig config, TerminalMetrics metrics) {
+        this.config = config;
+        this.metrics = metrics;
+        tabs.add(new Tab(config, metrics));
+
+        root.setFocusTraversable(true);
+        root.setBackground(new Background(new BackgroundFill(GAP_BACKGROUND, CornerRadii.EMPTY, null)));
+        root.getChildren().setAll(paneLayer, tabBar);
+        root.setOnMousePressed(event -> root.requestFocus());
+    }
+
+    public Parent node() {
+        return root;
+    }
+
+    public void requestFocus() {
+        root.requestFocus();
+    }
+
+    public void setFont(String family, double size) {
+        metrics.setFont(family, size);
+        nodes.values().forEach(TerminalPaneNode::discard);
+        markSceneDirty();
+    }
+
+    // ---- Tabs and panes -------------------------------------------------------------
+
+    public boolean isEmpty() {
+        return tabs.isEmpty();
+    }
+
+    public TerminalPane activePane() {
+        return currentTab().activePane();
+    }
+
+    public void navigate(Direction direction) {
+        if (!isEmpty() && currentTab().navigate(direction)) {
+            markSceneDirty();
+        }
+    }
+
+    public void toggleFloating() {
+        if (isEmpty()) {
+            return;
+        }
+        currentTab().toggleFloating();
+        markSceneDirty();
+    }
+
+    public void createPane() {
+        if (isEmpty()) {
+            return;
+        }
+        currentTab().createPane();
+        markSceneDirty();
+    }
+
+    public void closeActivePane() {
+        if (isEmpty()) {
+            return;
+        }
+        currentTab().closeActivePane();
+        if (currentTab().isEmpty()) {
+            tabs.remove(currentTabIndex);
+            if (currentTabIndex >= tabs.size()) {
+                currentTabIndex = Math.max(0, tabs.size() - 1);
+            }
+        }
+        markSceneDirty();
+    }
+
+    public void newTab() {
+        tabs.add(new Tab(config, metrics));
+        currentTabIndex = tabs.size() - 1;
+        markSceneDirty();
+    }
+
+    public void nextTab() {
+        if (tabs.size() > 1) {
+            currentTabIndex = (currentTabIndex + 1) % tabs.size();
+            markSceneDirty();
+        }
+    }
+
+    public void previousTab() {
+        if (tabs.size() > 1) {
+            currentTabIndex = (currentTabIndex - 1 + tabs.size()) % tabs.size();
+            markSceneDirty();
+        }
+    }
+
+    public void close() {
+        for (Tab tab : tabs) {
+            tab.close();
+        }
+        tabs.clear();
+        nodes.clear();
+        paneLayer.getChildren().clear();
+    }
+
+    private Tab currentTab() {
+        return tabs.get(currentTabIndex);
+    }
+
+    private List<TerminalPane> currentPanes() {
+        return tabs.isEmpty() ? List.of() : currentTab().panes();
+    }
+
+    private List<TerminalPane> allOpenPanes() {
+        List<TerminalPane> panes = new ArrayList<>();
+        for (Tab tab : tabs) {
+            panes.addAll(tab.allPanes());
+        }
+        return panes;
+    }
+
+    private boolean isActive(TerminalPane pane) {
+        return !tabs.isEmpty() && currentTab().isActive(pane);
+    }
+
+    private void focus(TerminalPane pane) {
+        if (!tabs.isEmpty() && currentTab().focus(pane)) {
+            markSceneDirty();
+        }
+    }
+
+    // ---- Rendering ------------------------------------------------------------------
+
+    public void render() {
+        double width = root.getWidth();
+        double height = root.getHeight();
+        long contentVersion = tabs.isEmpty() ? 0 : currentTab().contentVersion();
+        boolean geometryChanged = width != lastWidth || height != lastHeight;
+        boolean contentChanged = contentVersion != lastContentVersion;
+        boolean syncScene = sceneDirty || geometryChanged;
+
+        if (!syncScene && !contentChanged) {
+            return;
+        }
+
+        lastWidth = width;
+        lastHeight = height;
+        lastContentVersion = contentVersion;
+        sceneDirty = false;
+        if (syncScene) {
+            syncSceneGraph(width, height);
+        }
+        renderVisiblePanes();
+    }
+
+    private void markSceneDirty() {
+        sceneDirty = true;
+    }
+
+    private void syncSceneGraph(double width, double height) {
+        double topInset = tabs.size() > 1 ? TAB_BAR_HEIGHT : 0.0;
+
+        paneLayer.resizeRelocate(0.0, 0.0, width, height);
+        updateTabBar(width, topInset);
+
+        if (!tabs.isEmpty()) {
+            currentTab().layout(width, height, topInset);
+        }
+
+        List<TerminalPane> panes = currentPanes();
+        retainNodes(allOpenPanes());
+        List<TerminalPaneNode> orderedNodes = new ArrayList<>(panes.size());
+        for (TerminalPane pane : panes) {
+            pane.fitToBounds();
+            TerminalPaneNode node = nodeFor(pane);
+            node.resizeRelocate(Math.round(pane.x()), Math.round(pane.y()), pane.width(), pane.height());
+            orderedNodes.add(node);
+        }
+        paneLayer.getChildren().setAll(orderedNodes);
+    }
+
+    private void renderVisiblePanes() {
+        for (TerminalPane pane : currentPanes()) {
+            TerminalPaneNode node = nodes.get(pane);
+            if (node != null) {
+                node.renderIncremental(isActive(pane));
+            }
+        }
+    }
+
+    private TerminalPaneNode nodeFor(TerminalPane pane) {
+        return nodes.computeIfAbsent(pane, this::createNode);
+    }
+
+    private TerminalPaneNode createNode(TerminalPane pane) {
+        TerminalPaneNode node = new TerminalPaneNode(pane, metrics);
+        node.setOnMousePressed(event -> handleMousePressed(pane, event));
+        node.setOnMouseReleased(event -> handleMouseReleased(pane, event));
+        node.setOnMouseDragged(event -> handleMouseDragged(pane, event));
+        node.setOnMouseMoved(event -> handleMouseMoved(pane, event));
+        node.setOnScroll(event -> handleScroll(pane, event));
+        return node;
+    }
+
+    private void retainNodes(List<TerminalPane> openPanes) {
+        Set<TerminalPane> open = new HashSet<>(openPanes);
+        nodes.keySet().removeIf(pane -> !open.contains(pane));
+    }
+
+    private void updateTabBar(double width, double barHeight) {
+        tabBar.setVisible(barHeight > 0.0);
+        tabBar.setManaged(false);
+        tabBar.resizeRelocate(0.0, 0.0, width, barHeight);
+        tabBar.getChildren().clear();
+        if (barHeight <= 0.0) {
+            return;
+        }
+
+        double segmentWidth = width / tabs.size();
+        for (int i = 0; i < tabs.size(); i++) {
+            Label label = new Label(Integer.toString(i + 1));
+            boolean current = i == currentTabIndex;
+            label.setAlignment(Pos.CENTER);
+            label.setTextFill(current ? TAB_TEXT : TAB_INACTIVE_TEXT);
+            label.setBackground(new Background(new BackgroundFill(
+                    current ? TAB_ACTIVE_BACKGROUND : TAB_INACTIVE_BACKGROUND,
+                    CornerRadii.EMPTY,
+                    null)));
+            label.setFont(javafx.scene.text.Font.font(metrics.fontFamily(), Math.max(9.0, Math.min(13.0, barHeight * 0.62))));
+            label.setMinSize(0.0, barHeight);
+            label.setPrefSize(Math.max(0.0, segmentWidth - 1.0), barHeight);
+            label.setMaxSize(Double.MAX_VALUE, barHeight);
+            final int index = i;
+            label.setOnMousePressed(event -> {
+                currentTabIndex = index;
+                markSceneDirty();
+                root.requestFocus();
+                event.consume();
+            });
+            tabBar.getChildren().add(label);
+        }
+    }
+
+    // ---- Input ----------------------------------------------------------------------
+
+    private void handleMousePressed(TerminalPane pane, MouseEvent event) {
+        root.requestFocus();
+        focus(pane);
+        pressedButton = mouseButton(event);
+        mouseButtonPressed = true;
+        MouseTarget target = mouseTarget(pane);
+        if (target == null) {
+            return;
+        }
+        send(pane, target, MouseInput.press(pressedButton, localX(event.getX(), target), localY(event.getY(), target), modifiers(event)), true, event);
+    }
+
+    private void handleMouseReleased(TerminalPane pane, MouseEvent event) {
+        MouseButton button = pressedButton == MouseButton.UNKNOWN ? mouseButton(event) : pressedButton;
+        MouseTarget target = mouseTarget(pane);
+        if (target != null) {
+            send(pane, target, MouseInput.release(button, localX(event.getX(), target), localY(event.getY(), target), modifiers(event)), false, event);
+        }
+        mouseButtonPressed = false;
+        pressedButton = MouseButton.UNKNOWN;
+    }
+
+    private void handleMouseDragged(TerminalPane pane, MouseEvent event) {
+        MouseButton button = pressedButton == MouseButton.UNKNOWN ? mouseButton(event) : pressedButton;
+        MouseTarget target = mouseTarget(pane);
+        if (target == null) {
+            return;
+        }
+        send(pane, target, MouseInput.drag(button, localX(event.getX(), target), localY(event.getY(), target), modifiers(event)), true, event);
+    }
+
+    private void handleMouseMoved(TerminalPane pane, MouseEvent event) {
+        MouseTarget target = mouseTarget(pane);
+        if (target == null) {
+            return;
+        }
+        send(pane, target, MouseInput.motion(localX(event.getX(), target), localY(event.getY(), target), modifiers(event)), mouseButtonPressed, event);
+    }
+
+    private void handleScroll(TerminalPane pane, ScrollEvent event) {
+        root.requestFocus();
+        focus(pane);
+        int direction = scrollDirection(event);
+        if (direction == 0) {
+            return;
+        }
+
+        MouseButton wheelButton = direction > 0 ? MouseButton.FOUR : MouseButton.FIVE;
+        int rows = scrollRows(event);
+        MouseTarget target = mouseTarget(pane);
+        boolean sent = false;
+        if (target != null) {
+            double ex = localX(event.getX(), target);
+            double ey = localY(event.getY(), target);
+            KeyModifiers modifiers = modifiers(event);
+            for (int i = 0; i < rows; i++) {
+                if (!send(pane, target, MouseInput.press(wheelButton, ex, ey, modifiers), mouseButtonPressed, event)) {
+                    break;
+                }
+                sent = true;
+            }
+        }
+        if (!sent) {
+            pane.scrollViewport(direction > 0 ? -rows : rows);
+            event.consume();
+        }
+    }
+
+    private boolean send(TerminalPane pane, MouseTarget target, MouseInput input, boolean anyButtonPressed, InputEvent event) {
+        boolean sent = pane.sendMouse(input, target.size(), anyButtonPressed);
+        if (sent) {
+            event.consume();
+        }
+        return sent;
+    }
+
+    private MouseTarget mouseTarget(TerminalPane pane) {
+        if (pane.width() <= 2 * TerminalMetrics.PADDING || pane.height() <= 2 * TerminalMetrics.PADDING) {
+            return null;
+        }
+
+        int columns = metrics.columnsFor(pane.width());
+        int rows = metrics.rowsFor(pane.height());
+        long cellWidth = Math.max(1L, Math.round(metrics.cellWidth()));
+        long cellHeight = Math.max(1L, Math.round(metrics.lineHeight()));
+        long screenWidth = Math.max(1L, Math.round(columns * metrics.cellWidth()));
+        long screenHeight = Math.max(1L, Math.round(rows * metrics.lineHeight()));
+        return new MouseTarget(MouseEncoderSize.of(screenWidth, screenHeight, cellWidth, cellHeight), screenWidth, screenHeight);
+    }
+
+    private static double localX(double nodeX, MouseTarget target) {
+        return clamp(nodeX - TerminalMetrics.PADDING, 0.0, target.screenWidth() - 1.0);
+    }
+
+    private static double localY(double nodeY, MouseTarget target) {
+        return clamp(nodeY - TerminalMetrics.PADDING, 0.0, target.screenHeight() - 1.0);
+    }
+
+    private static double clamp(double value, double min, double max) {
+        return Math.max(min, Math.min(max, value));
+    }
+
+    private static KeyModifiers modifiers(MouseEvent event) {
+        return KeyModifiers.of(event.isShiftDown(), event.isControlDown(), event.isAltDown(), event.isMetaDown());
+    }
+
+    private static KeyModifiers modifiers(ScrollEvent event) {
+        return KeyModifiers.of(event.isShiftDown(), event.isControlDown(), event.isAltDown(), event.isMetaDown());
+    }
+
+    private static int scrollRows(ScrollEvent event) {
+        double rows;
+        if (event.getTextDeltaYUnits() == VerticalTextScrollUnits.LINES && event.getTextDeltaY() != 0.0) {
+            rows = Math.abs(event.getTextDeltaY());
+        } else if (event.getTextDeltaYUnits() == VerticalTextScrollUnits.PAGES && event.getTextDeltaY() != 0.0) {
+            rows = Math.abs(event.getTextDeltaY()) * 24.0;
+        } else if (event.getMultiplierY() > 0.0) {
+            rows = Math.abs(event.getDeltaY()) / event.getMultiplierY();
+        } else {
+            rows = Math.abs(event.getDeltaY()) / 40.0;
+        }
+        return Math.max(1, Math.min(64, (int) Math.ceil(rows)));
+    }
+
+    private static int scrollDirection(ScrollEvent event) {
+        if (event.getDeltaY() != 0.0) {
+            return event.getDeltaY() > 0.0 ? 1 : -1;
+        }
+        if (event.getTextDeltaYUnits() != VerticalTextScrollUnits.NONE && event.getTextDeltaY() != 0.0) {
+            return event.getTextDeltaY() > 0.0 ? 1 : -1;
+        }
+        return 0;
+    }
+
+    private static MouseButton mouseButton(MouseEvent event) {
+        return switch (event.getButton()) {
+            case PRIMARY -> MouseButton.LEFT;
+            case SECONDARY -> MouseButton.RIGHT;
+            case MIDDLE -> MouseButton.MIDDLE;
+            default -> MouseButton.UNKNOWN;
+        };
+    }
+
+    private record MouseTarget(MouseEncoderSize size, long screenWidth, long screenHeight) {
+    }
+}

src/main/java/com/gregor/jprototerm/Main.java

@@ -12,7 +12,6 @@ import javafx.scene.control.Spinner;
 import javafx.scene.control.SpinnerValueFactory;
 import javafx.scene.input.KeyEvent;
 import javafx.scene.layout.GridPane;
-import javafx.scene.layout.StackPane;
 import javafx.scene.text.Font;
 import javafx.stage.Stage;
 
@@ -21,79 +20,72 @@ import java.nio.file.Files;
 import java.nio.file.Path;
 
 public final class Main extends Application {
-    private TerminalWorkspace workspace;
+    private Compositor compositor;
-    private TerminalCanvasView terminalView;
+    private TerminalMetrics metrics;
     private AppConfig config;
 
     @Override
     public void start(Stage stage) {
         config = AppConfig.load();
 
-        workspace = new TerminalWorkspace(config);
+        metrics = new TerminalMetrics(config.fontFamily(), config.fontSize());
-        terminalView = new TerminalCanvasView(workspace, config);
+        compositor = new Compositor(config, metrics);
 
-        StackPane root = new StackPane(terminalView.canvas());
+        Scene scene = new Scene(compositor.node(), config.windowWidth(), config.windowHeight());
-        terminalView.canvas().widthProperty().bind(root.widthProperty());
-        terminalView.canvas().heightProperty().bind(root.heightProperty());
-
-        Scene scene = new Scene(root, config.windowWidth(), config.windowHeight());
         scene.addEventFilter(KeyEvent.KEY_PRESSED, this::handlePressed);
         scene.addEventFilter(KeyEvent.KEY_TYPED, event -> handleTyped(event));
 
         new AnimationTimer() {
             @Override
             public void handle(long now) {
-                terminalView.render();
+                compositor.render();
             }
         }.start();
 
         stage.setTitle("jprototerm");
         stage.setScene(scene);
         stage.setOnCloseRequest(event -> {
-            workspace.close();
+            compositor.close();
         });
         stage.show();
-        terminalView.canvas().requestFocus();
+        compositor.requestFocus();
     }
 
     private void handlePressed(KeyEvent event) {
         if (config.keybindings().get("navigate_left").matches(event)) {
-            workspace.navigate(Direction.LEFT);
+            compositor.navigate(Direction.LEFT);
             event.consume();
         } else if (config.keybindings().get("navigate_down").matches(event)) {
-            workspace.navigate(Direction.DOWN);
+            compositor.navigate(Direction.DOWN);
             event.consume();
         } else if (config.keybindings().get("navigate_up").matches(event)) {
-            workspace.navigate(Direction.UP);
+            compositor.navigate(Direction.UP);
             event.consume();
         } else if (config.keybindings().get("navigate_right").matches(event)) {
-            workspace.navigate(Direction.RIGHT);
+            compositor.navigate(Direction.RIGHT);
             event.consume();
         } else if (config.keybindings().get("toggle_floating").matches(event)) {
-            workspace.toggleFloating();
+            compositor.toggleFloating();
             event.consume();
         } else if (config.keybindings().get("new_pane").matches(event)) {
-            workspace.createPane();
+            compositor.createPane();
-            event.consume();
-        } else if (config.keybindings().get("next_floating").matches(event)) {
-            workspace.nextFloatingPane();
             event.consume();
         } else if (config.keybindings().get("close_pane").matches(event)) {
-            workspace.closeActivePane();
+            compositor.closeActivePane();
             event.consume();
-            if (workspace.isEmpty()) {
+            if (compositor.isEmpty()) {
                 // Closing the last pane quits the app.
-                workspace.close();
+                compositor.close();
                 Platform.exit();
             }
         } else if (config.keybindings().get("new_tab").matches(event)) {
-            workspace.newTab();
+            compositor.newTab();
             event.consume();
         } else if (config.keybindings().get("previous_tab").matches(event)) {
-            workspace.previousTab();
+            compositor.previousTab();
             event.consume();
         } else if (config.keybindings().get("next_tab").matches(event)) {
-            workspace.nextTab();
+            compositor.nextTab();
             event.consume();
         } else if (config.keybindings().get("open_font_selector").matches(event)) {
             openFontSelector();
@@ -104,7 +96,7 @@ public final class Main extends Application {
         } else {
             String encoded = KeyEncoder.encode(event);
             if (encoded != null) {
-                workspace.activePane().send(encoded);
+                compositor.activePane().send(encoded);
                 event.consume();
             }
         }
@@ -117,7 +109,7 @@ public final class Main extends Application {
 
         String text = event.getCharacter();
         if (text != null && !text.isEmpty() && text.charAt(0) >= 0x20 && text.charAt(0) != 0x7f) {
-            workspace.activePane().send(text);
+            compositor.activePane().send(text);
             event.consume();
         }
     }
@@ -160,18 +152,18 @@ public final class Main extends Application {
                     double selectedSize = size.getValue();
                     config = config.withFont(selectedFamily.trim(), selectedSize);
                     config.save();
-                    terminalView.setFont(config.fontFamily(), config.fontSize());
+                    compositor.setFont(config.fontFamily(), config.fontSize());
-                    terminalView.canvas().requestFocus();
+                    compositor.requestFocus();
                 });
     }
 
     private void openScrollbackInEditor() {
         try {
             Path file = Files.createTempFile("jprototerm-scrollback-", ".txt");
-            Files.writeString(file, workspace.activePane().scrollbackText());
+            Files.writeString(file, compositor.activePane().scrollbackText());
             file.toFile().deleteOnExit();
 
-            workspace.activePane().send(scrollbackEditorCommand(file) + "\r");
+            compositor.activePane().send(scrollbackEditorCommand(file) + "\r");
         } catch (IOException ex) {
             System.err.println("Could not open scrollback in editor: " + ex.getMessage());
         }

src/main/java/com/gregor/jprototerm/RenderProfiler.java

@@ -0,0 +1,79 @@
+package com.gregor.jprototerm;
+
+/**
+ * Lightweight render profiler, disabled unless {@code -Djprototerm.profile=true} (or the
+ * {@code JPROTOTERM_PROFILE=1} environment variable) is set. It accumulates wall-clock nanos
+ * into a handful of buckets and prints aggregate per-frame stats to stderr every
+ * {@code jprototerm.profile.frames} render invocations (default 120).
+ *
+ * <p>All render work runs on the JavaFX application thread, so the accumulators are plain
+ * fields with no synchronization.
+ *
+ * <p>Caveat: JavaFX canvas drawing is deferred to the QuantumRenderer thread, so the
+ * {@link #DRAW} bucket measures only the cost of <em>recording</em> draw commands, not the
+ * GPU paint. Pair this with {@code -Djavafx.pulseLogger=true} to see the render-thread side.
+ */
+final class RenderProfiler {
+    static final int SNAPSHOT = 0;
+    static final int FINGERPRINT = 1;
+    static final int DRAW = 2;
+    static final int FRAME = 3;
+    static final int UPDATE = 4;
+    static final int MARSHAL = 5;
+    private static final int BUCKETS = 6;
+    private static final String[] NAMES =
+            {"snapshot", "fingerprint", "draw", "frame-total", "update", "marshal"};
+
+    private static final boolean ENABLED =
+            Boolean.getBoolean("jprototerm.profile") || "1".equals(System.getenv("JPROTOTERM_PROFILE"));
+    private static final int DUMP_FRAMES = Integer.getInteger("jprototerm.profile.frames", 120);
+
+    private static final long[] totalNanos = new long[BUCKETS];
+    private static final long[] counts = new long[BUCKETS];
+    private static int frames;
+
+    private RenderProfiler() {
+    }
+
+    static boolean enabled() {
+        return ENABLED;
+    }
+
+    /** Returns a start timestamp, or 0 when profiling is disabled. */
+    static long start() {
+        return ENABLED ? System.nanoTime() : 0L;
+    }
+
+    /** Records the time elapsed since {@code startNanos} into {@code bucket}. */
+    static void stop(int bucket, long startNanos) {
+        if (!ENABLED) {
+            return;
+        }
+        totalNanos[bucket] += System.nanoTime() - startNanos;
+        counts[bucket]++;
+    }
+
+    /** Marks the end of one render invocation; dumps and resets every {@code DUMP_FRAMES}. */
+    static void frame() {
+        if (!ENABLED) {
+            return;
+        }
+        if (++frames < DUMP_FRAMES) {
+            return;
+        }
+        dump();
+    }
+
+    private static void dump() {
+        StringBuilder sb = new StringBuilder(192);
+        sb.append("[render-profile] ").append(frames).append(" renders");
+        for (int i = 0; i < BUCKETS; i++) {
+            double totalMs = totalNanos[i] / 1_000_000.0;
+            sb.append(String.format(" | %s %.3fms/f (n=%d)", NAMES[i], totalMs / frames, counts[i]));
+            totalNanos[i] = 0;
+            counts[i] = 0;
+        }
+        System.err.println(sb);
+        frames = 0;
+    }
+}

src/main/java/com/gregor/jprototerm/ShellSession.java

@@ -1,7 +1,5 @@
 package com.gregor.jprototerm;
 
-import javafx.application.Platform;
-
 import java.nio.charset.StandardCharsets;
 import java.util.HashMap;
 import java.util.Map;
@@ -94,23 +92,25 @@ public final class ShellSession implements AutoCloseable {
     }
 
     private void readOutput(TerminalPane pane) {
-        byte[] buffer = new byte[8192];
+        byte[] buffer = new byte[65536];
         try {
             int read;
             while ((read = pty.read(buffer)) != -1) {
-                if (!closed) {
+                if (closed) {
-                    byte[] bytes = new byte[read];
+                    break;
-                    System.arraycopy(buffer, 0, bytes, 0, read);
-                    Platform.runLater(() -> {
-                        if (!closed) {
-                            pane.write(bytes);
-                        }
-                    });
                 }
+                byte[] bytes = new byte[read];
+                System.arraycopy(buffer, 0, bytes, 0, read);
+                // Feed the terminal model straight from the reader thread. terminal access is
+                // guarded by the per-terminal lock, and the render loop picks the change up on
+                // the next pulse. Avoiding a Platform.runLater hop per chunk removes a frame of
+                // latency and stops write tasks from contending with rendering on the FX thread
+                // when a TUI repaints heavily (the input-lag culprit).
+                pane.write(bytes);
             }
         } catch (RuntimeException ex) {
             if (!closed) {
-                Platform.runLater(() -> pane.write("\r\nshell output stopped: " + ex.getMessage() + "\r\n"));
+                pane.write("\r\nshell output stopped: " + ex.getMessage() + "\r\n");
             }
         }
     }

src/main/java/com/gregor/jprototerm/Tab.java

@@ -3,244 +3,223 @@ package com.gregor.jprototerm;
 import java.util.ArrayList;
 import java.util.Comparator;
 import java.util.List;
+import java.util.stream.Stream;
 
 /**
- * One tab: an isolated stack of panes (tiled + floating) with its own active pane and
+ * One tab: a row of tiled panes with a group of floating panes shown over them. Floating panes
- * stashed-floating state. {@link TerminalWorkspace} owns the list of tabs and renders only
+ * are shown/hidden as a group ({@code floatingVisible}), and there is always at least one tiled
- * the current one. Mutating methods return whether they actually changed anything so the
+ * pane — a floating pane is promoted if the last tiled one closes — so the layout always has a
- * workspace can bump its render version conditionally.
+ * base. The {@link Compositor} owns the tabs and renders only the current one; mutating methods
+ * return whether they actually changed anything so it can bump its layout version.
  */
 final class Tab implements AutoCloseable {
     private final AppConfig config;
-    private final List<TerminalPane> panes = new ArrayList<>();
+    private final TerminalMetrics metrics;
-    private int activeIndex;
+    private final List<TerminalPane> tiled = new ArrayList<>();
-    private int hiddenFloatingFocusIndex = -1;
+    private final List<TerminalPane> floating = new ArrayList<>();
+    private boolean floatingVisible;
+    private TerminalPane active;
+    // The floating pane to re-focus when the group is shown again, and to prefer when promoting
+    // after the last tiled pane closes.
     private TerminalPane lastFocusedFloating;
+    // Last laid-out size, so a newly opened pane can be created at roughly its eventual rect
+    // (and thus grid). Seeded from the configured window size for the first pane, which is
+    // opened before any layout pass runs.
+    private double lastWidth;
+    private double lastHeight;
+    private double lastTopInset;
+    // Bumped whenever one of this tab's panes changes content; the compositor reads the current
+    // tab's value each frame as an O(1) "anything to repaint?" check.
+    private long contentVersion;
 
-    Tab(AppConfig config) {
+    Tab(AppConfig config, TerminalMetrics metrics) {
         this.config = config;
-        panes.add(openPane(false));
+        this.metrics = metrics;
+        this.lastWidth = config.windowWidth();
+        this.lastHeight = config.windowHeight();
+        TerminalPane first = openPane(false);
+        tiled.add(first);
+        active = first;
     }
 
     TerminalPane activePane() {
-        return panes.get(activeIndex);
+        return active;
     }
 
     boolean isEmpty() {
-        return panes.isEmpty();
+        return tiled.isEmpty() && floating.isEmpty();
     }
 
-    List<TerminalPane> panes() {
+    long contentVersion() {
-        if (panes.isEmpty()) {
+        return contentVersion;
-            return List.of();
+    }
-        }
-        List<TerminalPane> visible = panes.stream().filter(TerminalPane::visible).toList();
-        TerminalPane active = activePane();
-        if (!active.visible() || !active.floating()) {
-            return visible;
-        }
 
-        List<TerminalPane> ordered = new ArrayList<>(visible.size());
+    /**
-        visible.stream()
+     * Panes to composite, bottom-to-top: tiled first, then (when shown) the floating group with
-                .filter(pane -> pane != active)
+     * the active floating pane on top.
-                .forEach(ordered::add);
+     */
-        ordered.add(active);
+    List<TerminalPane> panes() {
+        if (!floatingVisible || floating.isEmpty()) {
+            return List.copyOf(tiled);
+        }
+        List<TerminalPane> ordered = new ArrayList<>(tiled.size() + floating.size());
+        ordered.addAll(tiled);
+        for (TerminalPane pane : floating) {
+            if (pane != active) {
+                ordered.add(pane);
+            }
+        }
+        if (floating.contains(active)) {
+            ordered.add(active); // active floating pane on top
+        }
         return List.copyOf(ordered);
     }
 
+    List<TerminalPane> allPanes() {
+        List<TerminalPane> all = new ArrayList<>(tiled.size() + floating.size());
+        all.addAll(tiled);
+        all.addAll(floating);
+        return List.copyOf(all);
+    }
+
     boolean isActive(TerminalPane pane) {
-        return !panes.isEmpty() && activePane() == pane;
+        return pane != null && pane == active;
     }
 
     boolean focus(TerminalPane pane) {
-        int index = panes.indexOf(pane);
+        if (pane == active || !isFocusable(pane)) {
-        if (index >= 0 && pane.visible() && activeIndex != index) {
+            return false;
-            setActive(index);
-            return true;
         }
-        return false;
+        setActive(pane);
+        return true;
     }
 
     void layout(double width, double height, double topInset) {
+        this.lastWidth = width;
+        this.lastHeight = height;
+        this.lastTopInset = topInset;
         double availHeight = height - topInset;
-        List<TerminalPane> tiled = panes.stream()
+
-                .filter(TerminalPane::visible)
+        double tileWidth = width / Math.max(1, tiled.size());
-                .filter(pane -> !pane.floating())
-                .toList();
-        int tileCount = Math.max(1, tiled.size());
-        double tileWidth = width / tileCount;
         for (int i = 0; i < tiled.size(); i++) {
             tiled.get(i).bounds(i * tileWidth, topInset, tileWidth, availHeight);
         }
 
-        List<TerminalPane> floating = panes.stream()
+        double floatingWidth = Math.max(420, width * 0.58);
-                .filter(TerminalPane::visible)
+        double floatingHeight = Math.max(260, availHeight * 0.58);
-                .filter(TerminalPane::floating)
-                .toList();
         for (int i = 0; i < floating.size(); i++) {
-            TerminalPane pane = floating.get(i);
-            double floatingWidth = Math.max(420, width * 0.58);
-            double floatingHeight = Math.max(260, availHeight * 0.58);
             double offset = i * 28.0;
-            pane.bounds(
+            floating.get(i).bounds(
                     Math.min(width - floatingWidth - 12.0, ((width - floatingWidth) / 2.0) + offset),
                     Math.min(height - floatingHeight - 12.0, topInset + ((availHeight - floatingHeight) / 2.0) + offset),
                     floatingWidth,
-                    floatingHeight
+                    floatingHeight);
-            );
         }
     }
 
     boolean navigate(Direction direction) {
-        TerminalPane current = activePane();
+        if (floating.contains(active) && navigateFloatingStack(direction)) {
-        if (current.floating() && navigateFloatingStack(direction)) {
             return true;
         }
-
+        TerminalPane target = focusable()
-        TerminalPane target = panes.stream()
+                .filter(pane -> pane != active)
-                .filter(TerminalPane::visible)
+                .filter(pane -> directionFilter(direction, active, pane))
-                .filter(pane -> pane != current)
+                .min(Comparator.comparingDouble(pane -> distance(active, pane)))
-                .filter(pane -> directionFilter(direction, current, pane))
-                .min(Comparator.comparingDouble(pane -> distance(current, pane)))
                 .orElse(null);
         if (target != null) {
-            setActive(panes.indexOf(target));
+            setActive(target);
             return true;
         }
         return false;
     }
 
     void toggleFloating() {
-        List<TerminalPane> floating = panes.stream()
-                .filter(TerminalPane::floating)
-                .toList();
         if (floating.isEmpty()) {
             createFloatingPane();
             return;
         }
-
+        if (floatingVisible) {
-        boolean anyVisible = floating.stream().anyMatch(TerminalPane::visible);
+            floatingVisible = false;
-        if (anyVisible) {
+            if (floating.contains(active)) {
-            TerminalPane active = activePane();
+                setActive(tiled.get(0));
-            hiddenFloatingFocusIndex = active.floating() ? activeIndex : firstVisibleFloatingIndex();
+            }
-            floating.forEach(pane -> pane.setVisible(false));
-            setActive(firstVisibleNonFloatingIndex());
         } else {
-            floating.forEach(pane -> pane.setVisible(true));
+            floatingVisible = true;
-            setActive(visibleIndexOrFallback(hiddenFloatingFocusIndex, panes.indexOf(floating.get(floating.size() - 1))));
+            setActive(floating.contains(lastFocusedFloating) ? lastFocusedFloating : floating.get(floating.size() - 1));
-            hiddenFloatingFocusIndex = -1;
         }
     }
 
-    /**
+    /** Adds a floating pane while the floating group is shown, otherwise a tiled pane. */
-     * "New pane": adds a floating pane while floating panes are shown, otherwise adds a
-     * tiled pane (the tiled row is redistributed equally by the layout).
-     */
     void createPane() {
-        if (anyFloatingVisible()) {
+        if (floatingVisible) {
             createFloatingPane();
         } else {
             TerminalPane pane = openPane(false);
-            panes.add(pane);
+            tiled.add(pane);
-            setActive(panes.size() - 1);
+            setActive(pane);
         }
     }
 
-    void nextFloatingPane() {
-        TerminalPane next = nextFloatingAfter(activeIndex);
-        next.setVisible(true);
-        setActive(panes.indexOf(next));
-    }
-
     void closeActivePane() {
-        TerminalPane active = activePane();
+        TerminalPane closing = active;
-        int removed = activeIndex;
+        boolean wasFloating = floating.remove(closing);
-        int previous = previousVisibleIndex(removed);
+        if (!wasFloating) {
-        panes.remove(removed);
+            tiled.remove(closing);
-        if (active == lastFocusedFloating) {
+        }
+        if (closing == lastFocusedFloating) {
             lastFocusedFloating = null;
         }
-        active.close();
+        closing.close();
-        if (panes.isEmpty()) {
+
-            activeIndex = 0;
+        if (tiled.isEmpty() && floating.isEmpty()) {
+            active = null; // tab is now empty; the compositor drops it
             return;
         }
-        activeIndex = adjustIndexAfterRemoval(previous, removed);
-        hiddenFloatingFocusIndex = adjustHiddenFocusAfterRemoval(hiddenFloatingFocusIndex, removed);
 
-        // If the last tiled (main) pane was closed, promote a floating pane to be the new
+        // Always keep a tiled base: if the last tiled pane just closed, promote a floating one
-        // main pane so the layout has a base and rendering continues normally. Prefer the
+        // (preferring the last focused).
-        // most recently focused floating pane.
+        if (tiled.isEmpty()) {
-        if (panes.stream().noneMatch(pane -> !pane.floating())) {
+            TerminalPane promote = floating.contains(lastFocusedFloating) ? lastFocusedFloating : floating.get(0);
-            TerminalPane promote = (lastFocusedFloating != null && panes.contains(lastFocusedFloating))
+            var promoteIndex = floating.indexOf(promote);
-                    ? lastFocusedFloating
+            var nextFocussed = promoteIndex == 0 ? 0 : promoteIndex - 1;
-                    : panes.get(activeIndex);
+            floating.remove(promote);
-            promote.setFloating(false);
+            tiled.add(promote);
-            promote.setVisible(true);
+            if (promote == lastFocusedFloating) {
-            activeIndex = panes.indexOf(promote);
+                lastFocusedFloating = null;
-            lastFocusedFloating = null;
+                if (!floating.isEmpty()) {
+                    lastFocusedFloating = floating.isEmpty() ? null : floating.get(nextFocussed);
+                }
+            }
+        }
+        if (floating.isEmpty()) {
+            floatingVisible = false;
         }
 
-        // If only hidden panes remained, reveal the one we're focusing so the screen isn't
+        setActive(wasFloating && floatingVisible ? floating.get(floating.size() - 1) : tiled.get(0));
-        // blank.
-        if (!panes.get(activeIndex).visible()) {
-            panes.get(activeIndex).setVisible(true);
-        }
     }
 
-    private void setActive(int index) {
+    private void setActive(TerminalPane pane) {
-        activeIndex = index;
+        active = pane;
-        if (index >= 0 && index < panes.size() && panes.get(index).floating()) {
+        if (floating.contains(pane)) {
-            lastFocusedFloating = panes.get(index);
+            lastFocusedFloating = pane;
         }
     }
 
     private void createFloatingPane() {
         TerminalPane pane = openPane(true);
-        panes.add(pane);
+        floating.add(pane);
-        setActive(panes.size() - 1);
+        floatingVisible = true;
-    }
+        setActive(pane);
-
-    private boolean anyFloatingVisible() {
-        return panes.stream().anyMatch(pane -> pane.floating() && pane.visible());
-    }
-
-    private TerminalPane nextFloatingAfter(int index) {
-        for (int i = index + 1; i < panes.size(); i++) {
-            TerminalPane pane = panes.get(i);
-            if (pane.floating()) {
-                return pane;
-            }
-        }
-        for (int i = 0; i <= index && i < panes.size(); i++) {
-            TerminalPane pane = panes.get(i);
-            if (pane.floating()) {
-                return pane;
-            }
-        }
-        return createAndReturnFloatingPane();
-    }
-
-    private TerminalPane createAndReturnFloatingPane() {
-        TerminalPane pane = openPane(true);
-        panes.add(pane);
-        return pane;
     }
 
     private boolean navigateFloatingStack(Direction direction) {
-        List<TerminalPane> floating = panes.stream()
-                .filter(TerminalPane::visible)
-                .filter(TerminalPane::floating)
-                .toList();
         if (floating.size() < 2) {
             return false;
         }
-
+        int current = floating.indexOf(active);
-        int current = floating.indexOf(activePane());
         if (current < 0) {
             return false;
         }
-
         int next = switch (direction) {
             case LEFT, UP -> current - 1;
             case DOWN, RIGHT -> current + 1;
@@ -248,71 +227,35 @@ final class Tab implements AutoCloseable {
         if (next < 0 || next >= floating.size()) {
             return false;
         }
-
+        setActive(floating.get(next));
-        setActive(panes.indexOf(floating.get(next)));
         return true;
     }
 
-    private int firstVisibleFloatingIndex() {
+    private boolean isFocusable(TerminalPane pane) {
-        for (int i = 0; i < panes.size(); i++) {
+        return tiled.contains(pane) || (floatingVisible && floating.contains(pane));
-            TerminalPane pane = panes.get(i);
-            if (pane.visible() && pane.floating()) {
-                return i;
-            }
-        }
-        return -1;
     }
 
-    private int firstVisibleNonFloatingIndex() {
+    private Stream<TerminalPane> focusable() {
-        for (int i = 0; i < panes.size(); i++) {
+        return floatingVisible ? Stream.concat(tiled.stream(), floating.stream()) : tiled.stream();
-            TerminalPane pane = panes.get(i);
-            if (pane.visible() && !pane.floating()) {
-                return i;
-            }
-        }
-        return 0;
     }
 
-    private int previousVisibleIndex(int index) {
+    private void markContentChanged() {
-        for (int i = index - 1; i >= 0; i--) {
+        contentVersion++;
-            if (panes.get(i).visible()) {
-                return i;
-            }
-        }
-        for (int i = index + 1; i < panes.size(); i++) {
-            if (panes.get(i).visible()) {
-                return i;
-            }
-        }
-        return firstVisibleNonFloatingIndex();
     }
 
-    private int visibleIndexOrFallback(int index, int fallback) {
+    private TerminalPane openPane(boolean asFloating) {
-        if (index >= 0 && index < panes.size() && panes.get(index).visible()) {
+        double availHeight = lastHeight - lastTopInset;
-            return index;
+        double widthPx;
+        double heightPx;
+        if (asFloating) {
+            widthPx = Math.max(420, lastWidth * 0.58);
+            heightPx = Math.max(260, availHeight * 0.58);
+        } else {
+            // A new tiled pane joins the row, so each gets 1/(n+1) of the width.
+            widthPx = lastWidth / (tiled.size() + 1);
+            heightPx = availHeight;
         }
-        return fallback;
+        return TerminalPane.create(config, metrics, this::markContentChanged, widthPx, heightPx);
-    }
-
-    private static int adjustIndexAfterRemoval(int index, int removedIndex) {
-        if (index < 0) {
-            return 0;
-        }
-        return index > removedIndex ? index - 1 : index;
-    }
-
-    private static int adjustHiddenFocusAfterRemoval(int index, int removedIndex) {
-        if (index < 0 || index == removedIndex) {
-            return -1;
-        }
-        return index > removedIndex ? index - 1 : index;
-    }
-
-    private TerminalPane openPane(boolean floating) {
-        TerminalPane pane = TerminalPane.create(config.columns(), config.rows(), config.maxScrollback());
-        pane.setFloating(floating);
-        pane.attach(ShellSession.start(config.shell(), config.envOverride(), pane, config.columns(), config.rows()));
-        return pane;
     }
 
     private static boolean directionFilter(Direction direction, TerminalPane current, TerminalPane candidate) {
@@ -337,9 +280,9 @@ final class Tab implements AutoCloseable {
 
     @Override
     public void close() {
-        for (TerminalPane pane : panes) {
+        tiled.forEach(TerminalPane::close);
-            pane.close();
+        floating.forEach(TerminalPane::close);
-        }
+        tiled.clear();
-        panes.clear();
+        floating.clear();
     }
 }

src/main/java/com/gregor/jprototerm/TerminalMetrics.java

@@ -0,0 +1,86 @@
+package com.gregor.jprototerm;
+
+import javafx.scene.text.Font;
+import javafx.scene.text.Text;
+
+/**
+ * Cell geometry shared by the {@link Compositor} and every {@link TerminalPane}.
+ *
+ * <p>The nominal cell width/height come from measuring the font, but a grid can't use
+ * fractional cells, so the measured size is snapped to whole (logical) pixels here — that
+ * snapping is why the value isn't purely a property of the font. The compositor owns the
+ * single instance (it holds the canvas, which is the pixel context), hands it to panes so
+ * they can turn their rect into a column/row count themselves, and re-measures it on a font
+ * change so every pane observes the new geometry through the shared reference.
+ */
+public final class TerminalMetrics {
+    /** Inset, in pixels, between a pane's edge and its content on every side. */
+    public static final double PADDING = 12.0;
+
+    private String fontFamily;
+    private double fontSize;
+    private Font font;
+    private double cellWidth;
+    private double lineHeight;
+    private double baselineOffset;
+
+    public TerminalMetrics(String fontFamily, double fontSize) {
+        setFont(fontFamily, fontSize);
+    }
+
+    public void setFont(String fontFamily, double fontSize) {
+        this.fontFamily = fontFamily;
+        this.fontSize = fontSize;
+        this.font = Font.font(fontFamily, fontSize);
+        measure(font);
+    }
+
+    public String fontFamily() {
+        return fontFamily;
+    }
+
+    public double fontSize() {
+        return fontSize;
+    }
+
+    public Font font() {
+        return font;
+    }
+
+    public double cellWidth() {
+        return cellWidth;
+    }
+
+    public double lineHeight() {
+        return lineHeight;
+    }
+
+    public double baselineOffset() {
+        return baselineOffset;
+    }
+
+    /** Columns that fit in a pane of the given pixel width (after subtracting the padding). */
+    public int columnsFor(double widthPx) {
+        return Math.max(1, (int) ((widthPx - 2 * PADDING) / cellWidth));
+    }
+
+    /** Rows that fit in a pane of the given pixel height (after subtracting the padding). */
+    public int rowsFor(double heightPx) {
+        return Math.max(1, (int) ((heightPx - 2 * PADDING) / lineHeight));
+    }
+
+    private void measure(Font font) {
+        Text text = new Text("┃MgÅjy");
+        text.setFont(font);
+        // Snap the cell size to whole pixels so cells tile on integer boundaries. Fractional
+        // cell metrics put every cell edge on a sub-pixel position, leaving anti-aliased
+        // seams that show up as a faint grid behind the themed cell backgrounds. Rounding
+        // leaves a few pixels of unused space at the right/bottom edge, which is fine.
+        this.lineHeight = Math.max(1.0, Math.round(text.getLayoutBounds().getHeight()));
+        this.baselineOffset = -text.getLayoutBounds().getMinY();
+
+        Text cell = new Text("M");
+        cell.setFont(font);
+        this.cellWidth = Math.max(1.0, Math.round(cell.getLayoutBounds().getWidth()));
+    }
+}

src/main/java/com/gregor/jprototerm/TerminalPane.java

@@ -1,5 +1,6 @@
 package com.gregor.jprototerm;
 
+import dev.jlibghostty.DeviceAttributes;
 import dev.jlibghostty.Ghostty;
 import dev.jlibghostty.KittyGraphics;
 import dev.jlibghostty.MouseAction;
@@ -11,29 +12,28 @@ import dev.jlibghostty.RenderStateSnapshot;
 import dev.jlibghostty.ScrollViewport;
 import dev.jlibghostty.Terminal;
 import dev.jlibghostty.TerminalOptions;
-import dev.jlibghostty.DeviceAttributes;
 
 import java.util.Optional;
 import java.util.concurrent.atomic.AtomicLong;
 
+/**
+ * One terminal: owns its ghostty {@link Terminal}, the {@link ShellSession}/pty driving it,
+ * and its on-screen geometry and grid. It does not draw itself; {@link TerminalPaneNode}
+ * reads snapshots from it and represents the visible rows and kitty graphics as JavaFX nodes.
+ */
 public final class TerminalPane implements AutoCloseable {
-    // Monotonic across all panes, bumped on every content change. Lets the renderer detect
-    // "nothing changed" in O(1) without scanning panes or building a render key.
-    private static final AtomicLong RENDER_TICK = new AtomicLong();
-
-    public static long renderTick() {
-        return RENDER_TICK.get();
-    }
-
     private final Terminal terminal;
+    private final TerminalMetrics metrics;
+    private final boolean kittyEnabled;
+    // Run on every content change so the owning tab can bump its content version — the
+    // compositor's O(1) "did the current tab change?" gate.
+    private final Runnable onContentChange;
     private final MouseEncoder mouseEncoder = new MouseEncoder();
-    // A persistent render state (reused across frames) is what makes ghostty's per-row
+    // A persistent render state (reused across frames) is what makes ghostty's per-row dirty
-    // dirty tracking meaningful: update() accumulates dirty since the last resetDirty().
+    // tracking meaningful: update() accumulates dirty since the last resetDirty().
     private final RenderState renderState = new RenderState();
     private RenderStateSnapshot cachedSnapshot;
     private ShellSession session;
-    private boolean floating;
-    private boolean visible = true;
     private double x;
     private double y;
     private double width;
@@ -42,23 +42,48 @@ public final class TerminalPane implements AutoCloseable {
     private int rows;
     private int pixelWidth;
     private int pixelHeight;
-    private long renderVersion;
+    private final AtomicLong contentVersion = new AtomicLong();
-    private long snapshotVersion = -1;
+    private volatile long snapshotVersion = -1;
 
-    private TerminalPane(Terminal terminal, int columns, int rows) {
+    private TerminalPane(Terminal terminal, TerminalMetrics metrics, boolean kittyEnabled,
+            Runnable onContentChange, int columns, int rows) {
         this.terminal = terminal;
+        this.metrics = metrics;
+        this.kittyEnabled = kittyEnabled;
+        this.onContentChange = onContentChange;
         this.columns = columns;
         this.rows = rows;
     }
 
-    public static TerminalPane create(int columns, int rows, long maxScrollback) {
+    /**
-        Terminal terminal = Ghostty.open(new TerminalOptions(columns, rows, maxScrollback));
+     * Opens a pane sized to fit the given pixel rect: the shared cell metrics decide how many
+     * columns and rows fit, and that grid is handed to ghostty and the shell at start-up. A
+     * non-positive size falls back to the configured default grid (used before the first
+     * layout, when no rect is known yet). The pane owns the shell session it starts and runs
+     * {@code onContentChange} on every content change.
+     */
+    public static TerminalPane create(AppConfig config, TerminalMetrics metrics, Runnable onContentChange, double widthPx, double heightPx) {
+        int columns = widthPx > 0 ? metrics.columnsFor(widthPx) : config.columns();
+        int rows = heightPx > 0 ? metrics.rowsFor(heightPx) : config.rows();
+        Terminal terminal = Ghostty.open(new TerminalOptions(columns, rows, config.maxScrollback()));
         terminal.setDeviceAttributesProvider(DeviceAttributes::xtermCompatible);
-        TerminalPane pane = new TerminalPane(terminal, columns, rows);
+        TerminalPane pane = new TerminalPane(terminal, metrics, config.kittyGraphics(), onContentChange, columns, rows);
         pane.refresh();
+        pane.attach(ShellSession.start(config.shell(), config.envOverride(), pane, columns, rows));
         return pane;
     }
 
+    private void attach(ShellSession session) {
+        this.session = session;
+        terminal.setPtyWriter(bytes -> {
+            ShellSession current = this.session;
+            if (current != null) {
+                current.send(bytes);
+            }
+        });
+        session.startReading(this);
+    }
+
     public void write(String text) {
         synchronized (terminal) {
             terminal.write(text);
@@ -73,17 +98,6 @@ public final class TerminalPane implements AutoCloseable {
         }
     }
 
-    public void attach(ShellSession session) {
-        this.session = session;
-        terminal.setPtyWriter(bytes -> {
-            ShellSession current = this.session;
-            if (current != null) {
-                current.send(bytes);
-            }
-        });
-        session.startReading(this);
-    }
-
     public void send(String text) {
         scrollViewportToBottom();
         if (session != null) {
@@ -117,7 +131,7 @@ public final class TerminalPane implements AutoCloseable {
         }
     }
 
-    public void scrollViewportToBottom() {
+    private void scrollViewportToBottom() {
         synchronized (terminal) {
             terminal.scrollViewport(ScrollViewport.bottom());
             refresh();
@@ -130,30 +144,39 @@ public final class TerminalPane implements AutoCloseable {
      * Snapshotting is deferred here rather than done in refresh(), so a burst of writes
      * between two frames collapses into a single snapshot.
      */
-    public RenderStateSnapshot renderSnapshot() {
+    public RenderStateSnapshot snapshot() {
-        return snapshot(false);
+        return takeSnapshot(false);
     }
 
     /**
      * Full snapshot with every row's cells populated. Used where the whole pane is redrawn
      * regardless of dirty state (the kitty-graphics path).
      */
-    public RenderStateSnapshot renderSnapshotFull() {
+    public RenderStateSnapshot snapshotFull() {
-        return snapshot(true);
+        return takeSnapshot(true);
     }
 
-    private RenderStateSnapshot snapshot(boolean full) {
+    private RenderStateSnapshot takeSnapshot(boolean full) {
         synchronized (terminal) {
+            long version = contentVersion.get();
             if (full) {
+                long updateStart = RenderProfiler.start();
                 renderState.update(terminal);
+                RenderProfiler.stop(RenderProfiler.UPDATE, updateStart);
+                long marshalStart = RenderProfiler.start();
                 cachedSnapshot = renderState.snapshot();
+                RenderProfiler.stop(RenderProfiler.MARSHAL, marshalStart);
                 renderState.resetDirty();
-                snapshotVersion = renderVersion;
+                snapshotVersion = version;
-            } else if (snapshotVersion != renderVersion) {
+            } else if (snapshotVersion != version) {
+                long updateStart = RenderProfiler.start();
                 renderState.update(terminal);
+                RenderProfiler.stop(RenderProfiler.UPDATE, updateStart);
+                long marshalStart = RenderProfiler.start();
                 cachedSnapshot = renderState.snapshotIncremental();
+                RenderProfiler.stop(RenderProfiler.MARSHAL, marshalStart);
                 renderState.resetDirty();
-                snapshotVersion = renderVersion;
+                snapshotVersion = version;
             }
             return cachedSnapshot;
         }
@@ -165,8 +188,17 @@ public final class TerminalPane implements AutoCloseable {
         }
     }
 
-    public long renderVersion() {
+    /** This pane's own content revision, bumped on every change (see {@link #refresh()}). */
-        return renderVersion;
+    public long contentVersion() {
+        return contentVersion.get();
+    }
+
+    long snapshotVersion() {
+        return snapshotVersion;
+    }
+
+    public boolean kittyEnabled() {
+        return kittyEnabled;
     }
 
     public Optional<KittyGraphics> kittyGraphics() {
@@ -175,22 +207,6 @@ public final class TerminalPane implements AutoCloseable {
         }
     }
 
-    public boolean floating() {
-        return floating;
-    }
-
-    public void setFloating(boolean floating) {
-        this.floating = floating;
-    }
-
-    public boolean visible() {
-        return visible;
-    }
-
-    public void setVisible(boolean visible) {
-        this.visible = visible;
-    }
-
     public double x() {
         return x;
     }
@@ -214,7 +230,14 @@ public final class TerminalPane implements AutoCloseable {
         this.height = height;
     }
 
-    public void resize(int columns, int rows, int pixelWidth, int pixelHeight) {
+    /** Recompute the ghostty grid from the current bounds and the shared cell metrics. */
+    public void fitToBounds() {
+        int columns = metrics.columnsFor(width);
+        int rows = metrics.rowsFor(height);
+        resize(columns, rows, (int) Math.round(metrics.cellWidth()), (int) Math.round(metrics.lineHeight()));
+    }
+
+    private void resize(int columns, int rows, int pixelWidth, int pixelHeight) {
         if (columns <= 0 || rows <= 0 || pixelWidth <= 0 || pixelHeight <= 0) {
             return;
         }
@@ -236,10 +259,11 @@ public final class TerminalPane implements AutoCloseable {
     }
 
     private void refresh() {
-        // Only mark the pane dirty; the snapshot itself is computed lazily in
+        // Mark this pane's content dirty (the snapshot is computed lazily in the paint path,
-        // renderSnapshot() so a burst of writes collapses into a single snapshot per frame.
+        // so a burst of writes collapses into one snapshot per frame) and tell the owning tab
-        renderVersion++;
+        // one of its panes changed.
-        RENDER_TICK.incrementAndGet();
+        contentVersion.incrementAndGet();
+        onContentChange.run();
     }
 
     @Override

src/main/java/com/gregor/jprototerm/TerminalWorkspace.java

@@ -1,139 +0,0 @@
-package com.gregor.jprototerm;
-
-import java.util.ArrayList;
-import java.util.List;
-
-/**
- * Holds the tabs and renders only the current one. Pane operations delegate to the current
- * tab; tab operations switch which tab is current. A single render version bumps on any
- * change (intra-tab or tab switch) so the renderer recomposites when needed.
- */
-public final class TerminalWorkspace implements AutoCloseable {
-    private final AppConfig config;
-    private final List<Tab> tabs = new ArrayList<>();
-    private int currentTab;
-    private long version;
-
-    public TerminalWorkspace(AppConfig config) {
-        this.config = config;
-        tabs.add(new Tab(config));
-    }
-
-    private Tab current() {
-        return tabs.get(currentTab);
-    }
-
-    public long version() {
-        return version;
-    }
-
-    public boolean isEmpty() {
-        return tabs.isEmpty();
-    }
-
-    public TerminalPane activePane() {
-        return current().activePane();
-    }
-
-    public List<TerminalPane> panes() {
-        return tabs.isEmpty() ? List.of() : current().panes();
-    }
-
-    public boolean isActive(TerminalPane pane) {
-        return !tabs.isEmpty() && current().isActive(pane);
-    }
-
-    public void layout(double width, double height, double topInset) {
-        if (!tabs.isEmpty()) {
-            current().layout(width, height, topInset);
-        }
-    }
-
-    public int tabCount() {
-        return tabs.size();
-    }
-
-    public int currentTabIndex() {
-        return currentTab;
-    }
-
-    public void focus(TerminalPane pane) {
-        if (!tabs.isEmpty() && current().focus(pane)) {
-            version++;
-        }
-    }
-
-    public void navigate(Direction direction) {
-        if (!tabs.isEmpty() && current().navigate(direction)) {
-            version++;
-        }
-    }
-
-    public void toggleFloating() {
-        if (tabs.isEmpty()) {
-            return;
-        }
-        current().toggleFloating();
-        version++;
-    }
-
-    public void createPane() {
-        if (tabs.isEmpty()) {
-            return;
-        }
-        current().createPane();
-        version++;
-    }
-
-    public void nextFloatingPane() {
-        if (tabs.isEmpty()) {
-            return;
-        }
-        current().nextFloatingPane();
-        version++;
-    }
-
-    public void closeActivePane() {
-        if (tabs.isEmpty()) {
-            return;
-        }
-        current().closeActivePane();
-        if (current().isEmpty()) {
-            // Closing a tab's last pane closes the tab. When no tabs remain the workspace
-            // is empty and Main quits.
-            tabs.remove(currentTab);
-            if (currentTab >= tabs.size()) {
-                currentTab = Math.max(0, tabs.size() - 1);
-            }
-        }
-        version++;
-    }
-
-    public void newTab() {
-        tabs.add(new Tab(config));
-        currentTab = tabs.size() - 1;
-        version++;
-    }
-
-    public void nextTab() {
-        if (tabs.size() > 1) {
-            currentTab = (currentTab + 1) % tabs.size();
-            version++;
-        }
-    }
-
-    public void previousTab() {
-        if (tabs.size() > 1) {
-            currentTab = (currentTab - 1 + tabs.size()) % tabs.size();
-            version++;
-        }
-    }
-
-    @Override
-    public void close() {
-        for (Tab tab : tabs) {
-            tab.close();
-        }
-        tabs.clear();
-    }
-}