Fix issue where SliverPersistentHeader that is both floating and pinned would...

Fix issue where SliverPersistentHeader that is both floating and pinned would scroll down when scrolling past the beginning of the ScrollView (#27433)

packages/flutter/lib/src/rendering/sliver_persistent_header.dart

@@ -524,6 +524,7 @@ abstract class RenderSliverFloatingPinnedPersistentHeader extends RenderSliverFl
     final double layoutExtent = maxExtent - constraints.scrollOffset;
     geometry = SliverGeometry(
       scrollExtent: maxExtent,
+      paintOrigin: math.min(constraints.overlap, 0.0),
       paintExtent: clampedPaintExtent,
       layoutExtent: layoutExtent.clamp(0.0, clampedPaintExtent),
       maxPaintExtent: maxExtent,

packages/flutter/test/widgets/slivers_appbar_floating_pinned_test.dart

@@ -112,4 +112,106 @@ void main() {
     expect(render.geometry.paintExtent, availableHeight);
     expect(render.geometry.layoutExtent, 0.0);
   });
+
+  testWidgets('Pinned and floating SliverAppBar sticks to top the content is scroll down', (WidgetTester tester) async {
+    const Key anchor = Key('drag');
+    await tester.pumpWidget(
+      MaterialApp(
+        home: Center(
+          child: Container(
+            height: 300,
+            color: Colors.green,
+            child: CustomScrollView(
+              physics: const BouncingScrollPhysics(),
+              slivers: <Widget>[
+                const SliverAppBar(
+                  pinned: true,
+                  floating: true,
+                  expandedHeight: 100.0,
+                ),
+                SliverToBoxAdapter(child: Container(key: anchor, color: Colors.red, height: 100)),
+                SliverToBoxAdapter(child: Container(height: 600, color: Colors.green)),
+              ],
+            ),
+          ),
+        ),
+      ),
+    );
+    final RenderSliverFloatingPinnedPersistentHeader render = tester.renderObject(find.byType(SliverAppBar));
+
+    const double scrollDistance = 40;
+    final TestGesture gesture = await tester.press(find.byKey(anchor));
+    await gesture.moveBy(const Offset(0, scrollDistance));
+    await tester.pump();
+
+    expect(render.geometry.paintOrigin, -scrollDistance);
+  });
+
+  testWidgets('Floating SliverAppBar sticks to top the content is scroll down', (WidgetTester tester) async {
+    const Key anchor = Key('drag');
+    await tester.pumpWidget(
+      MaterialApp(
+        home: Center(
+          child: Container(
+            height: 300,
+            color: Colors.green,
+            child: CustomScrollView(
+              physics: const BouncingScrollPhysics(),
+              slivers: <Widget>[
+                const SliverAppBar(
+                  pinned: false,
+                  floating: true,
+                  expandedHeight: 100.0,
+                ),
+                SliverToBoxAdapter(child: Container(key: anchor, color: Colors.red, height: 100)),
+                SliverToBoxAdapter(child: Container(height: 600, color: Colors.green)),
+              ],
+            ),
+          ),
+        ),
+      ),
+    );
+    final RenderSliverFloatingPersistentHeader render = tester.renderObject(find.byType(SliverAppBar));
+
+    const double scrollDistance = 40;
+    final TestGesture gesture = await tester.press(find.byKey(anchor));
+    await gesture.moveBy(const Offset(0, scrollDistance));
+    await tester.pump();
+
+    expect(render.geometry.paintOrigin, -scrollDistance);
+  });
+
+  testWidgets('Pinned SliverAppBar sticks to top the content is scroll down', (WidgetTester tester) async {
+    const Key anchor = Key('drag');
+    await tester.pumpWidget(
+      MaterialApp(
+        home: Center(
+          child: Container(
+            height: 300,
+            color: Colors.green,
+            child: CustomScrollView(
+              physics: const BouncingScrollPhysics(),
+              slivers: <Widget>[
+                const SliverAppBar(
+                  pinned: true,
+                  floating: false,
+                  expandedHeight: 100.0,
+                ),
+                SliverToBoxAdapter(child: Container(key: anchor, color: Colors.red, height: 100)),
+                SliverToBoxAdapter(child: Container(height: 600, color: Colors.green)),
+              ],
+            ),
+          ),
+        ),
+      ),
+    );
+    final RenderSliverPinnedPersistentHeader render = tester.renderObject(find.byType(SliverAppBar));
+
+    const double scrollDistance = 40;
+    final TestGesture gesture = await tester.press(find.byKey(anchor));
+    await gesture.moveBy(const Offset(0, scrollDistance));
+    await tester.pump();
+
+    expect(render.geometry.paintOrigin, -scrollDistance);
+  });
 }