port feasable performance improvements

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

@@ -365,7 +365,10 @@ public final class Compositor {
             double ey = localY(event.getY(), target);
             KeyModifiers modifiers = modifiers(event);
             for (int i = 0; i < rows; i++) {
-                sent |= send(pane, target, MouseInput.press(wheelButton, ex, ey, modifiers), mouseButtonPressed, event);
+                if (!send(pane, target, MouseInput.press(wheelButton, ex, ey, modifiers), mouseButtonPressed, event)) {
+                    break;
+                }
+                sent = true;
             }
         }
         if (!sent) {

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

@@ -14,6 +14,7 @@ import dev.jlibghostty.Terminal;
 import dev.jlibghostty.TerminalOptions;
 
 import java.util.Optional;
+import java.util.concurrent.atomic.AtomicLong;
 
 /**
  * One terminal: owns its ghostty {@link Terminal}, the {@link ShellSession}/pty driving it,
@@ -41,8 +42,8 @@ public final class TerminalPane implements AutoCloseable {
     private int rows;
     private int pixelWidth;
     private int pixelHeight;
-    private long contentVersion;
+    private final AtomicLong contentVersion = new AtomicLong();
-    private long snapshotVersion = -1;
+    private volatile long snapshotVersion = -1;
 
     private TerminalPane(Terminal terminal, TerminalMetrics metrics, boolean kittyEnabled,
             Runnable onContentChange, int columns, int rows) {
@@ -157,16 +158,17 @@ public final class TerminalPane implements AutoCloseable {
 
     private RenderStateSnapshot takeSnapshot(boolean full) {
         synchronized (terminal) {
+            long version = contentVersion.get();
             if (full) {
                 renderState.update(terminal);
                 cachedSnapshot = renderState.snapshot();
                 renderState.resetDirty();
-                snapshotVersion = contentVersion;
+                snapshotVersion = version;
-            } else if (snapshotVersion != contentVersion) {
+            } else if (snapshotVersion != version) {
                 renderState.update(terminal);
                 cachedSnapshot = renderState.snapshotIncremental();
                 renderState.resetDirty();
-                snapshotVersion = contentVersion;
+                snapshotVersion = version;
             }
             return cachedSnapshot;
         }
@@ -180,15 +182,11 @@ public final class TerminalPane implements AutoCloseable {
 
     /** This pane's own content revision, bumped on every change (see {@link #refresh()}). */
     public long contentVersion() {
-        synchronized (terminal) {
+        return contentVersion.get();
-            return contentVersion;
-        }
     }
 
     long snapshotVersion() {
-        synchronized (terminal) {
+        return snapshotVersion;
-            return snapshotVersion;
-        }
     }
 
     public boolean kittyEnabled() {
@@ -256,7 +254,7 @@ public final class TerminalPane implements AutoCloseable {
         // Mark this pane's content dirty (the snapshot is computed lazily in the paint path,
         // so a burst of writes collapses into one snapshot per frame) and tell the owning tab
         // one of its panes changed.
-        contentVersion++;
+        contentVersion.incrementAndGet();
         onContentChange.run();
     }
 

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

@@ -603,6 +603,27 @@ final class TerminalPaneNode extends Region {
         return cellBackgroundColor(firstCell ? cells.get(0) : cells.get(cells.size() - 1));
     }
 
+    private static Color cellBackgroundOverride(RenderCell cell) {
+        if (cell.inverse()) {
+            var fg = cell.foreground();
+            return fg.isPresent() ? toFxColor(fg.get()) : DEFAULT_FOREGROUND;
+        }
+        var bg = cell.background();
+        return bg.isPresent() ? toFxColor(bg.get()) : null;
+    }
+
+    private static Color cellForegroundColor(RenderCell cell) {
+        var fgOpt = cell.foreground();
+        var bgOpt = cell.background();
+        Color fg = fgOpt.isPresent() ? toFxColor(fgOpt.get()) : DEFAULT_FOREGROUND;
+        Color bg = bgOpt.isPresent() ? toFxColor(bgOpt.get()) : null;
+
+        if (cell.inverse()) {
+            return (bg != null) ? bg : PANE_BACKGROUND;
+        }
+        return fg;
+    }
+
     private static Color toFxColor(RenderColor color) {
         int key = (color.red() << 16) | (color.green() << 8) | color.blue();
         Color cached = COLOR_CACHE.get(key);
@@ -709,37 +730,61 @@ final class TerminalPaneNode extends Region {
             double contentTop = TerminalMetrics.PADDING + row.row() * lineHeight;
             double localCellTop = contentTop - rowTop;
             double baseline = TerminalMetrics.PADDING + metrics.baselineOffset() + row.row() * lineHeight - rowTop;
+            drawRowBackgrounds(gc, row, localCellTop, cellWidth, lineHeight);
+            drawRowText(gc, row, baseline, cellWidth);
+        }
+
+        private void drawRowBackgrounds(GraphicsContext gc, RenderRow row, double localCellTop, double cellWidth, double lineHeight) {
+            Color runBackground = null;
+            int runStartColumn = 0;
+            int previousColumn = -1;
             for (RenderCell cell : row.cells()) {
                 if (cell.kittyPlaceholder().isPresent()) {
+                    flushBackgroundRun(gc, runBackground, localCellTop, cellWidth, lineHeight, runStartColumn, previousColumn);
+                    runBackground = null;
+                    previousColumn = -1;
                     continue;
                 }
 
-                double x = TerminalMetrics.PADDING + cell.column() * cellWidth;
+                Color background = cell.selected() ? SELECTED_BACKGROUND : cellBackgroundOverride(cell);
-                var fgOpt = cell.foreground();
+                if (background == null) {
-                var bgOpt = cell.background();
+                    flushBackgroundRun(gc, runBackground, localCellTop, cellWidth, lineHeight, runStartColumn, previousColumn);
-                Color fg = fgOpt.isPresent() ? toFxColor(fgOpt.get()) : DEFAULT_FOREGROUND;
+                    runBackground = null;
-                Color bg = bgOpt.isPresent() ? toFxColor(bgOpt.get()) : null;
+                    previousColumn = -1;
-
-                if (cell.inverse()) {
-                    Color swappedBg = fg;
-                    fg = (bg != null) ? bg : PANE_BACKGROUND;
-                    bg = swappedBg;
-                }
-
-                if (bg != null) {
-                    gc.setFill(bg);
-                    gc.fillRect(x, localCellTop, cellWidth, lineHeight);
-                }
-                if (cell.selected()) {
-                    gc.setFill(SELECTED_BACKGROUND);
-                    gc.fillRect(x, localCellTop, cellWidth, lineHeight);
-                }
-                if (cell.codepoints().length == 0) {
                     continue;
                 }
 
-                gc.setFill(fg);
+                if (runBackground == null || background != runBackground || cell.column() != previousColumn + 1) {
-                gc.fillText(cell.text(), x, baseline);
+                    flushBackgroundRun(gc, runBackground, localCellTop, cellWidth, lineHeight, runStartColumn, previousColumn);
+                    runBackground = background;
+                    runStartColumn = cell.column();
+                }
+                previousColumn = cell.column();
+            }
+            flushBackgroundRun(gc, runBackground, localCellTop, cellWidth, lineHeight, runStartColumn, previousColumn);
+        }
+
+        private void flushBackgroundRun(GraphicsContext gc, Color background, double localCellTop,
+                double cellWidth, double lineHeight, int startColumn, int endColumn) {
+            if (background == null || endColumn < startColumn) {
+                return;
+            }
+            gc.setFill(background);
+            gc.fillRect(
+                    TerminalMetrics.PADDING + startColumn * cellWidth,
+                    localCellTop,
+                    (endColumn - startColumn + 1) * cellWidth,
+                    lineHeight);
+        }
+
+        private void drawRowText(GraphicsContext gc, RenderRow row, double baseline, double cellWidth) {
+            for (RenderCell cell : row.cells()) {
+                if (cell.kittyPlaceholder().isPresent() || cell.codepoints().length == 0) {
+                    continue;
+                }
+
+                gc.setFill(cellForegroundColor(cell));
+                gc.fillText(cell.text(), TerminalMetrics.PADDING + cell.column() * cellWidth, baseline);
             }
         }
     }