revert row diffing

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

@@ -51,8 +51,6 @@ final class GhosttyTerminalRenderer extends TerminalRenderer {
     private final TerminalMetrics metrics;
     // Decoded kitty images for this renderer's pane (kitty graphics state is per-terminal).
     private final Map<KittyImageKey, Image> kittyImageCache = new HashMap<>();
-    private long[] rowHashes = new long[0];
-    private CursorState lastCursor = CursorState.none();
 
     GhosttyTerminalRenderer(TerminalMetrics metrics) {
         this.metrics = metrics;
@@ -66,10 +64,8 @@ final class GhosttyTerminalRenderer extends TerminalRenderer {
         double height = target.height();
         gc.save();
         clip(gc, px, py, width, height, target.clip());
-        RenderStateSnapshot snapshot = target.snapshotFull();
+        drawContent(gc, target, target.snapshotFull(), px, py, width, height, active,
-        drawContent(gc, target, snapshot, px, py, width, height, active,
                 target.kittyEnabled() && hasKittyGraphics(target));
-        rememberSnapshot(snapshot);
         gc.restore();
     }
 
@@ -83,18 +79,12 @@ final class GhosttyTerminalRenderer extends TerminalRenderer {
         clip(gc, px, py, width, height, target.clip());
         if (target.kittyEnabled() && hasKittyGraphics(target)) {
             // Kitty placements can move without a per-row dirty flag, so always redraw whole.
-            RenderStateSnapshot snapshot = target.snapshotFull();
+            drawContent(gc, target, target.snapshotFull(), px, py, width, height, active, true);
-            drawContent(gc, target, snapshot, px, py, width, height, active, true);
-            rememberSnapshot(snapshot);
         } else {
             RenderStateSnapshot snapshot = target.snapshot();
             int dirty = snapshot == null ? DIRTY_FULL : snapshot.dirty();
             if (dirty == DIRTY_FULL) {
-                if (!drawChangedRows(gc, snapshot, px, py, width, height, active)) {
+                drawContent(gc, target, snapshot, px, py, width, height, active, false);
-                    RenderStateSnapshot fullSnapshot = target.snapshotFull();
-                    drawContent(gc, target, fullSnapshot, px, py, width, height, active, false);
-                    rememberSnapshot(fullSnapshot);
-                }
             } else if (dirty == DIRTY_PARTIAL) {
                 drawDirtyRows(gc, snapshot, px, py, width, height, active);
             }
@@ -103,86 +93,6 @@ final class GhosttyTerminalRenderer extends TerminalRenderer {
         gc.restore();
     }
 
-    // Some TUIs repaint the whole viewport for small logical changes. When ghostty gives us
-    // a full snapshot, compare row content with what we last painted and only redraw rows
-    // whose cells changed, plus old/new cursor rows because the cursor is an overlay.
-    private boolean drawChangedRows(
-            GraphicsContext gc,
-            RenderStateSnapshot snapshot,
-            double px,
-            double py,
-            double pw,
-            double ph,
-            boolean active
-    ) {
-        if (snapshot == null || rowHashes.length != snapshot.rows() || snapshot.renderRows().size() != snapshot.rows()) {
-            return false;
-        }
-
-        double cellWidth = metrics.cellWidth();
-        double lineHeight = metrics.lineHeight();
-        gc.setFontSmoothingType(FontSmoothingType.LCD);
-        gc.setFont(metrics.font());
-        double left = px + TerminalMetrics.PADDING;
-        double top = py + TerminalMetrics.PADDING;
-        double baseline = top + metrics.baselineOffset();
-        double contentBottom = top + snapshot.rows() * lineHeight;
-        int lastRow = snapshot.rows() - 1;
-
-        CursorState cursor = CursorState.from(snapshot);
-        long oldCursorRow = lastCursor.viewportRow();
-        long newCursorRow = cursor.viewportRow();
-        boolean cursorChanged = !cursor.equals(lastCursor);
-        double bandMin = Double.POSITIVE_INFINITY;
-        double bandMax = Double.NEGATIVE_INFINITY;
-
-        for (RenderRow row : snapshot.renderRows()) {
-            int rowIndex = row.row();
-            if (rowIndex < 0 || rowIndex >= rowHashes.length) {
-                return false;
-            }
-
-            long hash = rowHash(row);
-            boolean repaint = hash != rowHashes[rowIndex]
-                    || (cursorChanged && (rowIndex == oldCursorRow || rowIndex == newCursorRow));
-            if (!repaint) {
-                continue;
-            }
-
-            double y0 = Math.floor(top + (rowIndex * lineHeight));
-            double y1 = Math.ceil(top + ((rowIndex + 1) * lineHeight));
-            gc.setFill(PANE_BACKGROUND);
-            gc.fillRect(px, y0, pw, y1 - y0);
-            paintSidePadding(gc, row, px, pw, left, cellWidth, y0, y1 - y0);
-            drawRow(gc, row, left, top, baseline, cellWidth, lineHeight);
-            rowHashes[rowIndex] = hash;
-            bandMin = Math.min(bandMin, y0);
-            bandMax = Math.max(bandMax, y1);
-
-            if (rowIndex == 0) {
-                gc.setFill(rowEdgeBackground(row, true));
-                gc.fillRect(px, py, pw, top - py);
-                bandMin = Math.min(bandMin, py);
-            }
-            if (rowIndex == lastRow) {
-                gc.setFill(rowEdgeBackground(row, true));
-                gc.fillRect(px, contentBottom, pw, py + ph - contentBottom);
-                bandMax = Math.max(bandMax, py + ph);
-            }
-        }
-
-        lastCursor = cursor;
-        if (bandMin > bandMax) {
-            return true;
-        }
-        drawCursor(gc, snapshot, left, top, cellWidth, lineHeight);
-        gc.save();
-        clipRect(gc, px, bandMin, pw, bandMax - bandMin);
-        drawBorder(gc, px, py, pw, ph, active);
-        gc.restore();
-        return true;
-    }
-
     // Full content render: background, border, all rows, cursor, and (when enabled) kitty
     // graphics. Used by the kitty direct path and by full redraws.
     private void drawContent(
@@ -280,7 +190,6 @@ final class GhosttyTerminalRenderer extends TerminalRenderer {
             }
             paintSidePadding(gc, row, px, pw, left, cellWidth, y0, y1 - y0);
             drawRow(gc, row, left, top, baseline, cellWidth, lineHeight);
-            rememberRow(row);
             bandMin = Math.min(bandMin, y0);
             bandMax = Math.max(bandMax, y1);
             // Edge rows also own the top/bottom padding strip; repaint it and extend the
@@ -308,7 +217,6 @@ final class GhosttyTerminalRenderer extends TerminalRenderer {
         if (cursorRowDirty) {
             drawCursor(gc, snapshot, left, top, cellWidth, lineHeight);
         }
-        lastCursor = CursorState.from(snapshot);
         // Repainting rows clears the side borders within the band; restore just those
         // segments, clipped to the band so we don't redraw the whole outline.
         gc.save();
@@ -336,62 +244,6 @@ final class GhosttyTerminalRenderer extends TerminalRenderer {
         gc.strokeRect(x + 0.5, y + 0.5, width - 1.0, height - 1.0);
     }
 
-    private void rememberSnapshot(RenderStateSnapshot snapshot) {
-        if (snapshot == null) {
-            rowHashes = new long[0];
-            lastCursor = CursorState.none();
-            return;
-        }
-        if (rowHashes.length != snapshot.rows()) {
-            rowHashes = new long[snapshot.rows()];
-        }
-        for (RenderRow row : snapshot.renderRows()) {
-            rememberRow(row);
-        }
-        lastCursor = CursorState.from(snapshot);
-    }
-
-    private void rememberRow(RenderRow row) {
-        if (row.row() >= 0 && row.row() < rowHashes.length) {
-            rowHashes[row.row()] = rowHash(row);
-        }
-    }
-
-    private static long rowHash(RenderRow row) {
-        long hash = 0xcbf29ce484222325L;
-        hash = mix(hash, row.row());
-        for (RenderCell cell : row.cells()) {
-            hash = mix(hash, cell.column());
-            hash = mix(hash, cell.inverse() ? 1 : 0);
-            hash = mix(hash, cell.selected() ? 1 : 0);
-            hash = mixColor(hash, cell.foreground().orElse(null));
-            hash = mixColor(hash, cell.background().orElse(null));
-            for (int codepoint : cell.codepoints()) {
-                hash = mix(hash, codepoint);
-            }
-            if (cell.kittyPlaceholder().isPresent()) {
-                KittyPlaceholder placeholder = cell.kittyPlaceholder().get();
-                hash = mix(hash, placeholder.imageId());
-                hash = mix(hash, placeholder.placementId());
-                hash = mix(hash, placeholder.sourceRow());
-                hash = mix(hash, placeholder.sourceColumn());
-            }
-        }
-        return hash;
-    }
-
-    private static long mixColor(long hash, RenderColor color) {
-        if (color == null) {
-            return mix(hash, -1);
-        }
-        return mix(hash, (color.red() << 16) | (color.green() << 8) | color.blue());
-    }
-
-    private static long mix(long hash, long value) {
-        hash ^= value;
-        return hash * 0x100000001b3L;
-    }
-
     // Effective background colour of a cell as it is drawn (reverse video swaps fg/bg, an
     // unset colour falls back to the defaults).
     private static Color cellBackgroundColor(RenderCell cell) {
@@ -823,29 +675,6 @@ final class GhosttyTerminalRenderer extends TerminalRenderer {
     private record SourceRect(double x, double y, double width, double height) {
     }
 
-    private record CursorState(boolean visible, boolean hasViewport, long viewportX, long viewportY, RenderCursorStyle style) {
-        private static CursorState none() {
-            return new CursorState(false, false, -1, -1, null);
-        }
-
-        private static CursorState from(RenderStateSnapshot snapshot) {
-            if (snapshot == null) {
-                return none();
-            }
-            boolean hasViewport = snapshot.cursorViewportHasValue();
-            return new CursorState(
-                    snapshot.cursorVisible(),
-                    hasViewport,
-                    hasViewport ? snapshot.cursorViewportX() : -1,
-                    hasViewport ? snapshot.cursorViewportY() : -1,
-                    snapshot.cursorStyle());
-        }
-
-        private long viewportRow() {
-            return visible && hasViewport ? viewportY : -1;
-        }
-    }
-
     private static final class KittyPlaceholderBounds {
         private int minRow = Integer.MAX_VALUE;
         private int maxRow = Integer.MIN_VALUE;