From 16088cfc807712650d6994df75ddd2c99b4c4e32 Mon Sep 17 00:00:00 2001
From: fufesou <linlong1266@gmail.com>
Date: Sun, 13 Sep 2026 14:53:47 +0800
Subject: [PATCH] Synchronize custom-scrollbar cursor geometry after relayout

---
 flutter/lib/desktop/pages/remote_page.dart | 10 ++++++----
 flutter/lib/models/model.dart              |  2 +-
 flutter/test/cursor_scroll_edge_test.dart  | 20 +++++++++++---------
 3 files changed, 18 insertions(+), 14 deletions(-)

diff --git a/flutter/lib/desktop/pages/remote_page.dart b/flutter/lib/desktop/pages/remote_page.dart
index 1c9aa9901..735820e07 100644
--- a/flutter/lib/desktop/pages/remote_page.dart
+++ b/flutter/lib/desktop/pages/remote_page.dart
@@ -1173,7 +1173,7 @@ class _ImagePaintState extends State<ImagePaint> {
               child: child);
         });
     if (c.imageOverflow.isTrue && c.scrollStyle != ScrollStyle.scrollauto) {
-      _syncEdgeScrollAfterLayout(c);
+      _syncScrollAfterLayout(c);
       final paintWidth = c.getDisplayWidth() * s;
       final paintHeight = c.getDisplayHeight() * s;
       final paintSize = Size(paintWidth, paintHeight);
@@ -1218,13 +1218,15 @@ class _ImagePaintState extends State<ImagePaint> {
     }
   }
 
-  void _syncEdgeScrollAfterLayout(CanvasModel canvas) {
-    if (canvas.scrollStyle != ScrollStyle.scrolledge) return;
+  void _syncScrollAfterLayout(CanvasModel canvas) {
+    // Custom scrollbars also paint from scroll fractions; preserve Original's path.
+    if (canvas.scrollStyle != ScrollStyle.scrolledge &&
+        canvas.viewStyle.style != kRemoteViewStyleCustom) return;
     final renderedScroll = (canvas.scrollX, canvas.scrollY);
     // Relayout can clamp or detach scroll positions without a scroll event.
     SchedulerBinding.instance.addPostFrameCallback((_) {
       if (!mounted) return;
-      canvas.updateEdgeScrollAfterLayout(renderedScroll);
+      canvas.updateScrollAfterLayout(renderedScroll);
     });
   }
 
diff --git a/flutter/lib/models/model.dart b/flutter/lib/models/model.dart
index 0582571a7..01d5d79b8 100644
--- a/flutter/lib/models/model.dart
+++ b/flutter/lib/models/model.dart
@@ -2702,7 +2702,7 @@ class CanvasModel with ChangeNotifier {
     notifyListeners();
   }
 
-  void updateEdgeScrollAfterLayout((double, double) renderedScroll) {
+  void updateScrollAfterLayout((double, double) renderedScroll) {
     updateScrollPercent();
     // A delayed refresh may already have changed the model without repainting.
     if (renderedScroll != (_scrollX, _scrollY)) {
diff --git a/flutter/test/cursor_scroll_edge_test.dart b/flutter/test/cursor_scroll_edge_test.dart
index dc7e2ef8a..9a7f4f1aa 100644
--- a/flutter/test/cursor_scroll_edge_test.dart
+++ b/flutter/test/cursor_scroll_edge_test.dart
@@ -47,7 +47,7 @@ class _Texture extends Fake implements TextureModel {
 }
 
 class _ScrollCanvas extends CanvasModel {
-  _ScrollCanvas(FFI ffi, String style)
+  _ScrollCanvas(FFI ffi, String style, this.scrollStyle)
       : viewStyle = ViewStyle(
             style: style,
             width: _viewport.width,
@@ -69,7 +69,7 @@ class _ScrollCanvas extends CanvasModel {
   @override
   double get y => (size.height - getDisplayHeight() * scale) / 2;
   @override
-  ScrollStyle get scrollStyle => ScrollStyle.scrolledge;
+  final ScrollStyle scrollStyle;
   @override
   final ViewStyle viewStyle;
 
@@ -100,10 +100,10 @@ class _Cursor extends CursorModel {
 
 class _FFI extends Fake implements FFI {
   _FFI(ui.Image frame, ui.Image cursor,
-      {required bool texture, required String style, required Offset position})
+      {required bool texture, required (String, ScrollStyle) style, required Offset position})
       : ffiModel = _Peer(frame) {
     imageModel = _Image(this, frame, texture);
-    canvasModel = _ScrollCanvas(this, style);
+    canvasModel = _ScrollCanvas(this, style.$1, style.$2);
     cursorModel = _Cursor(this, cursor, position);
   }
   @override
@@ -131,7 +131,9 @@ class _Draw extends Fake implements Canvas {
 }
 
 void main() {
-  for (final style in [kRemoteViewStyleOriginal, kRemoteViewStyleCustom]) {
+  for (final style in [(kRemoteViewStyleOriginal, ScrollStyle.scrolledge),
+    (kRemoteViewStyleCustom, ScrollStyle.scrolledge),
+    (kRemoteViewStyleCustom, ScrollStyle.scrollbar)]) {
     for (final texture in [false, true]) {
       for (final (frame, dpr) in [
         (const Size(199, 320), 1.0),
@@ -140,13 +142,13 @@ void main() {
         (const Size(400, 158), 1.0),
       ]) {
         testWidgets(
-            'ScrollEdge $style texture=$texture frame=$frame DPR=$dpr',
+            'Scroll $style texture=$texture frame=$frame DPR=$dpr',
             (tester) => tester
                 .runAsync(() => _check(tester, (style, texture, frame, dpr))));
       }
       for (final refreshBeforeLayout in [true, false]) {
         testWidgets(
-            'ScrollEdge relayout $style texture=$texture early=$refreshBeforeLayout',
+            'Scroll relayout $style texture=$texture early=$refreshBeforeLayout',
             (tester) => tester.runAsync(() =>
                 _checkRelayout(tester, (style, texture, refreshBeforeLayout))));
       }
@@ -155,7 +157,7 @@ void main() {
 }
 
 Future<void> _check(
-    WidgetTester tester, (String, bool, Size, double) testCase) async {
+    WidgetTester tester, ((String, ScrollStyle), bool, Size, double) testCase) async {
   final (style, texture, frame, dpr) = testCase;
   tester.view.devicePixelRatio = dpr;
   tester.view.physicalSize = _viewport * dpr;
@@ -195,7 +197,7 @@ Future<void> _check(
 }
 
 Future<void> _checkRelayout(
-    WidgetTester tester, (String, bool, bool) testCase) async {
+    WidgetTester tester, ((String, ScrollStyle), bool, bool) testCase) async {
   final (style, texture, refreshBeforeLayout) = testCase;
   tester.view.devicePixelRatio = 1;
   tester.view.physicalSize = _viewport;