fixes nan

Author: chunhtai

shell/platform/darwin/ios/framework/Source/SemanticsObject.mm

@@ -221,16 +221,39 @@ - (id)accessibilityContainer {
 
 // private methods
 
+- (float)scrollExtentMax {
+  if (![_semanticsObject isAccessibilityBridgeAlive]) {
+    return 0.0;
+  }
+  float scrollExtentMax = _semanticsObject.node.scrollExtentMax;
+  if (isnan(scrollExtentMax)) {
+    scrollExtentMax = 0.0;
+  } else if (!isfinite(scrollExtentMax)) {
+    scrollExtentMax = kScrollExtentMaxForInf + [self scrollPosition];
+  }
+  return scrollExtentMax;
+}
+
+- (float)scrollPosition {
+  if (![_semanticsObject isAccessibilityBridgeAlive]) {
+    return 0.0;
+  }
+  float scrollPosition = _semanticsObject.node.scrollPosition;
+  if (isnan(scrollPosition)) {
+    scrollPosition = 0.0;
+  }
+  NSCAssert(isfinite(scrollPosition), @"The scrollPosition must not be infinity");
+  return scrollPosition;
+}
+
 - (CGSize)contentSizeInternal {
   CGRect result;
   const SkRect& rect = _semanticsObject.node.rect;
-  float scrollExtentMax = isfinite(_semanticsObject.node.scrollExtentMax)
-                              ? _semanticsObject.node.scrollExtentMax
-                              : kScrollExtentMaxForInf + _semanticsObject.node.scrollPosition;
+
   if (_semanticsObject.node.actions & flutter::kVerticalScrollSemanticsActions) {
-    result = CGRectMake(rect.x(), rect.y(), rect.width(), rect.height() + scrollExtentMax);
+    result = CGRectMake(rect.x(), rect.y(), rect.width(), rect.height() + [self scrollExtentMax]);
   } else if (_semanticsObject.node.actions & flutter::kHorizontalScrollSemanticsActions) {
-    result = CGRectMake(rect.x(), rect.y(), rect.width() + scrollExtentMax, rect.height());
+    result = CGRectMake(rect.x(), rect.y(), rect.width() + [self scrollExtentMax], rect.height());
   } else {
     result = CGRectMake(rect.x(), rect.y(), rect.width(), rect.height());
   }
@@ -242,11 +265,11 @@ - (CGPoint)contentOffsetInternal {
   CGPoint origin = self.frame.origin;
   const SkRect& rect = _semanticsObject.node.rect;
   if (_semanticsObject.node.actions & flutter::kVerticalScrollSemanticsActions) {
-    result = ConvertPointToGlobal(
-        _semanticsObject, CGPointMake(rect.x(), rect.y() + _semanticsObject.node.scrollPosition));
+    result = ConvertPointToGlobal(_semanticsObject,
+                                  CGPointMake(rect.x(), rect.y() + [self scrollPosition]));
   } else if (_semanticsObject.node.actions & flutter::kHorizontalScrollSemanticsActions) {
-    result = ConvertPointToGlobal(
-        _semanticsObject, CGPointMake(rect.x() + _semanticsObject.node.scrollPosition, rect.y()));
+    result = ConvertPointToGlobal(_semanticsObject,
+                                  CGPointMake(rect.x() + [self scrollPosition], rect.y()));
   } else {
     result = origin;
   }

shell/platform/darwin/ios/framework/Source/SemanticsObjectTest.mm

@@ -285,6 +285,44 @@ - (void)testCanHandleInfiniteScrollExtent {
                                     CGPointMake(0, scrollPosition * effectivelyScale)));
 }
 
+- (void)testCanHandleNaNScrollExtent {
+  fml::WeakPtrFactory<flutter::AccessibilityBridgeIos> factory(
+      new flutter::MockAccessibilityBridge());
+  fml::WeakPtr<flutter::AccessibilityBridgeIos> bridge = factory.GetWeakPtr();
+
+  float transformScale = 0.5f;
+  float screenScale = [[bridge->view() window] screen].scale;
+  float effectivelyScale = transformScale / screenScale;
+  float x = 10;
+  float y = 10;
+  float w = 100;
+  float h = 200;
+  float scrollExtentMax = std::nan("");
+  float scrollPosition = std::nan("");
+
+  flutter::SemanticsNode node;
+  node.flags = static_cast<int32_t>(flutter::SemanticsFlags::kHasImplicitScrolling);
+  node.actions = flutter::kVerticalScrollSemanticsActions;
+  node.rect = SkRect::MakeXYWH(x, y, w, h);
+  node.scrollExtentMax = scrollExtentMax;
+  node.scrollPosition = scrollPosition;
+  node.transform = {
+      transformScale, 0, 0, 0, 0, transformScale, 0, 0, 0, 0, transformScale, 0, 0, 0, 0, 1.0};
+  FlutterSemanticsObject* delegate = [[FlutterSemanticsObject alloc] initWithBridge:bridge uid:0];
+  FlutterScrollableSemanticsObject* scrollable =
+      [[FlutterScrollableSemanticsObject alloc] initWithSemanticsObject:delegate];
+  SemanticsObject* scrollable_object = static_cast<SemanticsObject*>(scrollable);
+  [scrollable_object setSemanticsNode:&node];
+  [scrollable_object accessibilityBridgeDidFinishUpdate];
+  XCTAssertTrue(
+      CGRectEqualToRect(scrollable.frame, CGRectMake(x * effectivelyScale, y * effectivelyScale,
+                                                     w * effectivelyScale, h * effectivelyScale)));
+  // Content size equal to the scrollable size.
+  XCTAssertTrue(CGSizeEqualToSize(scrollable.contentSize,
+                                  CGSizeMake(w * effectivelyScale, h * effectivelyScale)));
+  XCTAssertTrue(CGPointEqualToPoint(scrollable.contentOffset, CGPointMake(0, 0)));
+}
+
 - (void)testFlutterScrollableSemanticsObjectIsNotHittestable {
   fml::WeakPtrFactory<flutter::AccessibilityBridgeIos> factory(
       new flutter::MockAccessibilityBridge());