Schedule new frame in markNeedsPaint

Flutter-Bounty-Hunters · Oct 12, 2023 · ceafa68 · ceafa68
1 parent c28dd5f
commit ceafa68
Showing 1 changed file with 26 additions and 27 deletions.
diff --git a/lib/src/follower.dart b/lib/src/follower.dart
@@ -305,15 +305,28 @@ class RenderFollower extends RenderProxyBox {
   void attach(PipelineOwner owner) {
     super.attach(owner);
 
-    _link.addFollowerLayerTransformChangeListener(_followerLayerTransformChanged);
+    // We repaint whenever the `FollowerLayer` changes its transform. This is why.
+    //
+    // We had a bug where the initial layout of an iOS toolbar wasn't positioning
+    // its arrow in the expected place. It was found that the `FollowerLayer` was
+    // running `_establishTransform()` after this `RenderFollower` was done with
+    // layout and paint. The `FollowerLayer` wasn't settling on its final transform
+    // until after this `RenderFollower` was done doing all of its work, which meant
+    // that content within a `Follower` never got a chance to react to the final
+    // `Follower` offset, leading to the wrong arrow position.
+    //
+    // By running another paint pass whenever the `FollowerLayer` changes its
+    // transform, `Follower`s like the iOS toolbar can correctly position its
+    // content at least within 1 frame of the desired moment.
+    _link.addFollowerLayerTransformChangeListener(markNeedsPaint);
     if (repaintWhenLeaderChanges) {
       _link.addListener(_onLinkChange);
     }
   }
 
   @override
   void detach() {
-    _link.removeFollowerLayerTransformChangeListener(_followerLayerTransformChanged);
+    _link.removeFollowerLayerTransformChangeListener(markNeedsPaint);
     if (repaintWhenLeaderChanges) {
       _link.removeListener(_onLinkChange);
     }
@@ -334,14 +347,14 @@ class RenderFollower extends RenderProxyBox {
 
     FtlLogs.follower.fine("Setting new link - $value");
 
-    _link.removeFollowerLayerTransformChangeListener(_followerLayerTransformChanged);
+    _link.removeFollowerLayerTransformChangeListener(markNeedsPaint);
     if (repaintWhenLeaderChanges) {
       _link.removeListener(_onLinkChange);
     }
 
     _link = value;
 
-    _link.addFollowerLayerTransformChangeListener(_followerLayerTransformChanged);
+    _link.addFollowerLayerTransformChangeListener(markNeedsPaint);
     if (repaintWhenLeaderChanges) {
       _link.addListener(_onLinkChange);
     }
@@ -574,6 +587,15 @@ class RenderFollower extends RenderProxyBox {
     }
   }
 
+  @override
+  void markNeedsPaint() {
+    super.markNeedsPaint();
+
+    // Immediately schedule a new frame to avoid being in a dirty in the cases
+    // where markNeedsPaint and there are no other frames scheduled.
+    WidgetsBinding.instance.scheduleFrame();
+  }
+
   void _paintDebugVisuals(PaintingContext context) {
     if (!showDebugPaint) {
       return;
@@ -749,29 +771,6 @@ class RenderFollower extends RenderProxyBox {
     properties.add(DiagnosticsProperty<bool>('showWhenUnlinked', showWhenUnlinked));
     properties.add(TransformProperty('current transform matrix', _getCurrentTransform()));
   }
-
-  void _followerLayerTransformChanged() {
-    // We repaint whenever the `FollowerLayer` changes its transform. This is why.
-    //
-    // We had a bug where the initial layout of an iOS toolbar wasn't positioning
-    // its arrow in the expected place. It was found that the `FollowerLayer` was
-    // running `_establishTransform()` after this `RenderFollower` was done with
-    // layout and paint. The `FollowerLayer` wasn't settling on its final transform
-    // until after this `RenderFollower` was done doing all of its work, which meant
-    // that content within a `Follower` never got a chance to react to the final
-    // `Follower` offset, leading to the wrong arrow position.
-    //
-    // By running another paint pass whenever the `FollowerLayer` changes its
-    // transform, `Follower`s like the iOS toolbar can correctly position its
-    // content at least within 1 frame of the desired moment.
-    WidgetsBinding.instance.addPostFrameCallback((timeStamp) {
-      if (!attached) {
-        return;
-      }
-
-      markNeedsPaint();
-    });
-  }
 }
 
 /// A composited layer that applies a transformation matrix to its children such