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

This reverts commit 57103bb98b.

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/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/TerminalPane.java

@@ -160,13 +160,21 @@ public final class TerminalPane implements AutoCloseable {
         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 = version;
             } 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 = version;
             }

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

@@ -44,6 +44,12 @@ final class TerminalPaneNode extends Region {
     private static final int DIRTY_PARTIAL = 1;
     private static final int DIRTY_FULL = 2;
 
+    // Debug toggle: when set, skip the per-column repaint and always repaint the whole row.
+    // Used to bisect partial-repaint artifacts (stale black bars near the cursor).
+    private static final boolean FULL_ROW_REPAINT =
+            Boolean.getBoolean("jprototerm.fullRowRepaint")
+                    || "1".equals(System.getenv("JPROTOTERM_FULL_ROW_REPAINT"));
+
     private static final Color DEFAULT_FOREGROUND = Color.rgb(225, 229, 235);
     private static final Color SELECTED_BACKGROUND = Color.rgb(52, 92, 140);
     private static final Color PANE_BACKGROUND = Color.rgb(9, 10, 12);
@@ -91,7 +97,9 @@ final class TerminalPaneNode extends Region {
 
     void renderFull(boolean active) {
         prepareGeometry();
+        long snapshotStart = RenderProfiler.start();
         RenderStateSnapshot snapshot = pane.snapshotFull();
+        RenderProfiler.stop(RenderProfiler.SNAPSHOT, snapshotStart);
         long renderedVersion = pane.snapshotVersion();
         boolean withKitty = pane.kittyEnabled() && hasKittyGraphics();
         updateRowsFull(snapshot);
@@ -102,6 +110,13 @@ final class TerminalPaneNode extends Region {
     }
 
     void renderIncremental(boolean active) {
+        long frameStart = RenderProfiler.start();
+        renderIncrementalBody(active);
+        RenderProfiler.stop(RenderProfiler.FRAME, frameStart);
+        RenderProfiler.frame();
+    }
+
+    private void renderIncrementalBody(boolean active) {
         boolean geometryChanged = prepareGeometry();
         boolean withKitty = pane.kittyEnabled() && hasKittyGraphics();
         if (drawnContentVersion == Long.MIN_VALUE || geometryChanged || withKitty) {
@@ -113,7 +128,9 @@ final class TerminalPaneNode extends Region {
             return;
         }
 
+        long snapshotStart = RenderProfiler.start();
         RenderStateSnapshot snapshot = pane.snapshot();
+        RenderProfiler.stop(RenderProfiler.SNAPSHOT, snapshotStart);
         long renderedVersion = pane.snapshotVersion();
         int dirty = snapshot == null ? DIRTY_FULL : snapshot.dirty();
         if (dirty == DIRTY_FULL) {
@@ -167,7 +184,9 @@ final class TerminalPaneNode extends Region {
         Set<Integer> liveRows = new HashSet<>();
         for (RenderRow row : snapshot.renderRows()) {
             TerminalRowNode node = rowNode(row.row());
+            long fpStart = RenderProfiler.start();
             long fingerprint = rowFingerprint(row);
+            RenderProfiler.stop(RenderProfiler.FINGERPRINT, fpStart);
             node.render(row);
             rowFingerprints.put(row.row(), fingerprint);
             liveRows.add(row.row());
@@ -197,7 +216,9 @@ final class TerminalPaneNode extends Region {
                 continue;
             }
             TerminalRowNode node = rowNode(row.row());
+            long fpStart = RenderProfiler.start();
             long fingerprint = rowFingerprint(row);
+            RenderProfiler.stop(RenderProfiler.FINGERPRINT, fpStart);
             node.renderChanged(row);
             rowFingerprints.put(row.row(), fingerprint);
         }
@@ -212,7 +233,9 @@ final class TerminalPaneNode extends Region {
             return Set.of();
         }
 
+        long shiftStart = RenderProfiler.start();
         ShiftPlan plan = detectShift(snapshot, changedRows);
+        RenderProfiler.stop(RenderProfiler.FINGERPRINT, shiftStart);
         if (plan == null) {
             return Set.of();
         }
@@ -236,21 +259,29 @@ final class TerminalPaneNode extends Region {
     }
 
     private ShiftPlan detectShift(RenderStateSnapshot snapshot, List<RenderRow> changedRows) {
+        int rowCount = snapshot.rows();
+        int changedCount = changedRows.size();
+        // The new-content hash of each changed row is invariant across the delta scan below,
+        // so compute it once here instead of re-hashing the whole row for every candidate delta.
+        long[] changedHashes = new long[changedCount];
+        for (int i = 0; i < changedCount; i++) {
+            changedHashes[i] = rowFingerprint(changedRows.get(i));
+        }
+
         int bestDelta = 0;
         int bestScore = 0;
-        int rowCount = snapshot.rows();
         for (int delta = -rowCount + 1; delta < rowCount; delta++) {
             if (delta == 0) {
                 continue;
             }
             int score = 0;
-            for (RenderRow row : changedRows) {
+            for (int i = 0; i < changedCount; i++) {
-                int sourceRow = row.row() + delta;
+                int sourceRow = changedRows.get(i).row() + delta;
                 if (sourceRow < 0 || sourceRow >= rowCount || !rows.containsKey(sourceRow)) {
                     continue;
                 }
                 Long previous = rowFingerprints.get(sourceRow);
-                if (previous != null && previous == rowFingerprint(row)) {
+                if (previous != null && previous == changedHashes[i]) {
                     score++;
                 }
             }
@@ -267,13 +298,14 @@ final class TerminalPaneNode extends Region {
 
         List<RowMove> moves = new ArrayList<>(bestScore);
         Set<Integer> targetRows = new HashSet<>();
-        for (RenderRow row : changedRows) {
+        for (int i = 0; i < changedCount; i++) {
+            RenderRow row = changedRows.get(i);
             int sourceRow = row.row() + bestDelta;
             if (sourceRow < 0 || sourceRow >= rowCount || !rows.containsKey(sourceRow)) {
                 continue;
             }
             Long previous = rowFingerprints.get(sourceRow);
-            if (previous != null && previous == rowFingerprint(row)) {
+            if (previous != null && previous == changedHashes[i]) {
                 moves.add(new RowMove(sourceRow, row.row()));
                 targetRows.add(row.row());
             }
@@ -692,6 +724,7 @@ final class TerminalPaneNode extends Region {
         private void render(RenderRow row) {
             prepareCanvas(row);
 
+            long drawStart = RenderProfiler.start();
             GraphicsContext gc = canvas.getGraphicsContext2D();
             gc.clearRect(0.0, 0.0, canvas.getWidth(), canvas.getHeight());
             gc.setFontSmoothingType(FontSmoothingType.LCD);
@@ -699,14 +732,24 @@ final class TerminalPaneNode extends Region {
 
             paintSidePadding(gc, row, canvas.getWidth(), canvas.getHeight());
             drawRow(gc, row, rowTop(row), metrics.cellWidth(), metrics.lineHeight());
+            RenderProfiler.stop(RenderProfiler.DRAW, drawStart);
+
+            long fpStart = RenderProfiler.start();
             cellFingerprints = cellFingerprints(row);
+            RenderProfiler.stop(RenderProfiler.FINGERPRINT, fpStart);
         }
 
         private void renderChanged(RenderRow row) {
+            if (FULL_ROW_REPAINT) {
+                render(row);
+                return;
+            }
             double oldWidth = canvas.getWidth();
             double oldHeight = canvas.getHeight();
             prepareCanvas(row);
+            long fpStart = RenderProfiler.start();
             long[] nextFingerprints = cellFingerprints(row);
+            RenderProfiler.stop(RenderProfiler.FINGERPRINT, fpStart);
             if (cellFingerprints.length != nextFingerprints.length
                     || oldWidth != canvas.getWidth()
                     || oldHeight != canvas.getHeight()) {
@@ -714,6 +757,7 @@ final class TerminalPaneNode extends Region {
                 return;
             }
 
+            long drawStart = RenderProfiler.start();
             GraphicsContext gc = canvas.getGraphicsContext2D();
             gc.setFontSmoothingType(FontSmoothingType.LCD);
             gc.setFont(metrics.font());
@@ -741,6 +785,7 @@ final class TerminalPaneNode extends Region {
             if (runStart >= 0) {
                 repaintColumns(gc, row, runStart, runEnd);
             }
+            RenderProfiler.stop(RenderProfiler.DRAW, drawStart);
             cellFingerprints = nextFingerprints;
         }