Revert "Support scrolling in iOS accessibility (flutter#26671)" (flutter#26803)

This reverts commit e56dd3a.

Author: chunhtai

lib/ui/semantics/semantics_node.h

@@ -44,17 +44,12 @@ enum class SemanticsAction : int32_t {
   kSetText = 1 << 21,
 };
 
-const int kVerticalScrollSemanticsActions =
+const int kScrollableSemanticsActions =
+    static_cast<int32_t>(SemanticsAction::kScrollLeft) |
+    static_cast<int32_t>(SemanticsAction::kScrollRight) |
     static_cast<int32_t>(SemanticsAction::kScrollUp) |
     static_cast<int32_t>(SemanticsAction::kScrollDown);
 
-const int kHorizontalScrollSemanticsActions =
-    static_cast<int32_t>(SemanticsAction::kScrollLeft) |
-    static_cast<int32_t>(SemanticsAction::kScrollRight);
-
-const int kScrollableSemanticsActions =
-    kVerticalScrollSemanticsActions | kHorizontalScrollSemanticsActions;
-
 /// C/C++ representation of `SemanticsFlags` defined in
 /// `lib/ui/semantics.dart`.
 ///\warning This must match the `SemanticsFlags` enum in

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

@@ -31,7 +31,7 @@ constexpr int32_t kRootNodeId = 0;
  * The parent of this node in the node tree. Will be nil for the root node and
  * during transient state changes.
  */
-@property(nonatomic, assign) SemanticsObject* parent;
+@property(nonatomic, readonly) SemanticsObject* parent;
 
 /**
  * The accessibility bridge that this semantics object is attached to. This
@@ -94,14 +94,6 @@ constexpr int32_t kRootNodeId = 0;
 
 - (BOOL)onCustomAccessibilityAction:(FlutterCustomAccessibilityAction*)action;
 
-/**
- * Called after accessibility bridge finishes a semantics update.
- *
- * Subclasses can override this method if they contain states that can only be
- * updated once every node in the accessibility tree has finished updating.
- */
-- (void)accessibilityBridgeDidFinishUpdate;
-
 #pragma mark - Designated initializers
 
 - (instancetype)init __attribute__((unavailable("Use initWithBridge instead")));
@@ -167,18 +159,6 @@ constexpr int32_t kRootNodeId = 0;
 
 @end
 
-/// The semantics object for scrollable. This class creates an UIScrollView to interact with the
-/// iOS.
-@interface FlutterScrollableSemanticsObject : UIScrollView
-
-- (instancetype)init NS_UNAVAILABLE;
-- (instancetype)initWithFrame:(CGRect)frame NS_UNAVAILABLE;
-- (instancetype)initWithCoder:(NSCoder*)coder NS_UNAVAILABLE;
-- (instancetype)initWithSemanticsObject:(SemanticsObject*)semanticsObject NS_DESIGNATED_INITIALIZER;
-- (void)accessibilityBridgeDidFinishUpdate;
-
-@end
-
 /**
  * Represents a semantics object that has children and hence has to be presented to the OS as a
  * UIAccessibilityContainer.

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

@@ -34,58 +34,6 @@
   return flutter::SemanticsAction::kScrollUp;
 }
 
-SkM44 GetGlobalTransform(SemanticsObject* reference) {
-  SkM44 globalTransform = [reference node].transform;
-  for (SemanticsObject* parent = [reference parent]; parent; parent = parent.parent) {
-    globalTransform = parent.node.transform * globalTransform;
-  }
-  return globalTransform;
-}
-
-SkPoint ApplyTransform(SkPoint& point, const SkM44& transform) {
-  SkV4 vector = transform.map(point.x(), point.y(), 0, 1);
-  return SkPoint::Make(vector.x / vector.w, vector.y / vector.w);
-}
-
-CGPoint ConvertPointToGlobal(SemanticsObject* reference, CGPoint local_point) {
-  SkM44 globalTransform = GetGlobalTransform(reference);
-  SkPoint point = SkPoint::Make(local_point.x, local_point.y);
-  point = ApplyTransform(point, globalTransform);
-  // `rect` is in the physical pixel coordinate system. iOS expects the accessibility frame in
-  // the logical pixel coordinate system. Therefore, we divide by the `scale` (pixel ratio) to
-  // convert.
-  CGFloat scale = [[[reference bridge]->view() window] screen].scale;
-  auto result = CGPointMake(point.x() / scale, point.y() / scale);
-  return [[reference bridge]->view() convertPoint:result toView:nil];
-}
-
-CGRect ConvertRectToGlobal(SemanticsObject* reference, CGRect local_rect) {
-  SkM44 globalTransform = GetGlobalTransform(reference);
-
-  SkPoint quad[4] = {
-      SkPoint::Make(local_rect.origin.x, local_rect.origin.y),                          // top left
-      SkPoint::Make(local_rect.origin.x + local_rect.size.width, local_rect.origin.y),  // top right
-      SkPoint::Make(local_rect.origin.x + local_rect.size.width,
-                    local_rect.origin.y + local_rect.size.height),  // bottom right
-      SkPoint::Make(local_rect.origin.x,
-                    local_rect.origin.y + local_rect.size.height)  // bottom left
-  };
-  for (auto& point : quad) {
-    point = ApplyTransform(point, globalTransform);
-  }
-  SkRect rect;
-  NSCAssert(rect.setBoundsCheck(quad, 4), @"Transformed points can't form a rect");
-  rect.setBounds(quad, 4);
-
-  // `rect` is in the physical pixel coordinate system. iOS expects the accessibility frame in
-  // the logical pixel coordinate system. Therefore, we divide by the `scale` (pixel ratio) to
-  // convert.
-  CGFloat scale = [[[reference bridge]->view() window] screen].scale;
-  auto result =
-      CGRectMake(rect.x() / scale, rect.y() / scale, rect.width() / scale, rect.height() / scale);
-  return UIAccessibilityConvertFrameToScreenCoordinates(result, [reference bridge]->view());
-}
-
 }  // namespace
 
 @implementation FlutterSwitchSemanticsObject {
@@ -140,152 +88,6 @@ - (UIAccessibilityTraits)accessibilityTraits {
 
 @end  // FlutterSwitchSemanticsObject
 
-@interface FlutterScrollableSemanticsObject ()
-@property(nonatomic, strong) SemanticsObject* semanticsObject;
-@end
-
-@implementation FlutterScrollableSemanticsObject {
-  fml::scoped_nsobject<SemanticsObjectContainer> _container;
-}
-
-- (instancetype)initWithSemanticsObject:(SemanticsObject*)semanticsObject {
-  self = [super initWithFrame:CGRectZero];
-  if (self) {
-    _semanticsObject = [semanticsObject retain];
-    [semanticsObject.bridge->view() addSubview:self];
-  }
-  return self;
-}
-
-- (void)dealloc {
-  _container.get().semanticsObject = nil;
-  [_semanticsObject release];
-  [self removeFromSuperview];
-  [super dealloc];
-}
-
-- (UIView*)hitTest:(CGPoint)point withEvent:(UIEvent*)event {
-  return nil;
-}
-
-- (NSMethodSignature*)methodSignatureForSelector:(SEL)sel {
-  NSMethodSignature* result = [super methodSignatureForSelector:sel];
-  if (!result) {
-    result = [_semanticsObject methodSignatureForSelector:sel];
-  }
-  return result;
-}
-
-- (void)forwardInvocation:(NSInvocation*)anInvocation {
-  [anInvocation setTarget:_semanticsObject];
-  [anInvocation invoke];
-}
-
-- (void)accessibilityBridgeDidFinishUpdate {
-  // In order to make iOS think this UIScrollView is scrollable, the following
-  // requirements must be true.
-  // 1. contentSize must be bigger than the frame size.
-  // 2. The scrollable isAccessibilityElement must return YES
-  //
-  // Once the requirements are met, the iOS uses contentOffset to determine
-  // what scroll actions are available. e.g. If the view scrolls vertically and
-  // contentOffset is 0.0, only the scroll down action is available.
-  [self setFrame:[_semanticsObject accessibilityFrame]];
-  [self setContentSize:[self contentSizeInternal]];
-  [self setContentOffset:[self contentOffsetInternal] animated:NO];
-  if (self.contentSize.width > self.frame.size.width ||
-      self.contentSize.height > self.frame.size.height) {
-    self.isAccessibilityElement = YES;
-  } else {
-    self.isAccessibilityElement = NO;
-    ;
-  }
-}
-
-- (void)setChildren:(NSArray<SemanticsObject*>*)children {
-  [_semanticsObject setChildren:children];
-  // The children's parent is pointing to _semanticsObject, need to manually
-  // set it this object.
-  for (SemanticsObject* child in _semanticsObject.children) {
-    child.parent = (SemanticsObject*)self;
-  }
-}
-
-- (id)accessibilityContainer {
-  if (_container == nil) {
-    _container.reset([[SemanticsObjectContainer alloc]
-        initWithSemanticsObject:(SemanticsObject*)self
-                         bridge:[_semanticsObject bridge]]);
-  }
-  return _container.get();
-}
-
-// private methods
-
-- (CGSize)contentSizeInternal {
-  CGRect result;
-  const SkRect& rect = _semanticsObject.node.rect;
-  if (_semanticsObject.node.actions & flutter::kVerticalScrollSemanticsActions) {
-    result = CGRectMake(rect.x(), rect.y(), rect.width(),
-                        rect.height() + _semanticsObject.node.scrollExtentMax);
-  } else if (_semanticsObject.node.actions & flutter::kHorizontalScrollSemanticsActions) {
-    result = CGRectMake(rect.x(), rect.y(), rect.width() + _semanticsObject.node.scrollExtentMax,
-                        rect.height());
-  } else {
-    result = CGRectMake(rect.x(), rect.y(), rect.width(), rect.height());
-  }
-  return ConvertRectToGlobal(_semanticsObject, result).size;
-}
-
-- (CGPoint)contentOffsetInternal {
-  CGPoint result;
-  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));
-  } else if (_semanticsObject.node.actions & flutter::kHorizontalScrollSemanticsActions) {
-    result = ConvertPointToGlobal(
-        _semanticsObject, CGPointMake(rect.x() + _semanticsObject.node.scrollPosition, rect.y()));
-  } else {
-    result = origin;
-  }
-  return CGPointMake(result.x - origin.x, result.y - origin.y);
-}
-
-// The following methods are explicitly forwarded to the wrapped SemanticsObject because the
-// forwarding logic above doesn't apply to them since they are also implemented in the
-// UIScrollView class, the base class.
-
-- (BOOL)accessibilityActivate {
-  return [_semanticsObject accessibilityActivate];
-}
-
-- (void)accessibilityIncrement {
-  [_semanticsObject accessibilityIncrement];
-}
-
-- (void)accessibilityDecrement {
-  [_semanticsObject accessibilityDecrement];
-}
-
-- (BOOL)accessibilityScroll:(UIAccessibilityScrollDirection)direction {
-  return [_semanticsObject accessibilityScroll:direction];
-}
-
-- (BOOL)accessibilityPerformEscape {
-  return [_semanticsObject accessibilityPerformEscape];
-}
-
-- (void)accessibilityElementDidBecomeFocused {
-  [_semanticsObject accessibilityElementDidBecomeFocused];
-}
-
-- (void)accessibilityElementDidLoseFocus {
-  [_semanticsObject accessibilityElementDidLoseFocus];
-}
-@end  // FlutterScrollableSemanticsObject
-
 @implementation FlutterCustomAccessibilityAction {
 }
 @end
@@ -372,9 +174,6 @@ - (void)setSemanticsNode:(const flutter::SemanticsNode*)node {
   _node = *node;
 }
 
-- (void)accessibilityBridgeDidFinishUpdate { /* Do nothing by default */
-}
-
 /**
  * Whether calling `setSemanticsNode:` with `node` would cause a layout change.
  */
@@ -599,9 +398,27 @@ - (CGRect)accessibilityFrame {
 }
 
 - (CGRect)globalRect {
-  const SkRect& rect = [self node].rect;
-  CGRect localRect = CGRectMake(rect.x(), rect.y(), rect.width(), rect.height());
-  return ConvertRectToGlobal(self, localRect);
+  SkM44 globalTransform = [self node].transform;
+  for (SemanticsObject* parent = [self parent]; parent; parent = parent.parent) {
+    globalTransform = parent.node.transform * globalTransform;
+  }
+
+  SkPoint quad[4];
+  [self node].rect.toQuad(quad);
+  for (auto& point : quad) {
+    SkV4 vector = globalTransform.map(point.x(), point.y(), 0, 1);
+    point.set(vector.x / vector.w, vector.y / vector.w);
+  }
+  SkRect rect;
+  rect.setBounds(quad, 4);
+
+  // `rect` is in the physical pixel coordinate system. iOS expects the accessibility frame in
+  // the logical pixel coordinate system. Therefore, we divide by the `scale` (pixel ratio) to
+  // convert.
+  CGFloat scale = [[[self bridge]->view() window] screen].scale;
+  auto result =
+      CGRectMake(rect.x() / scale, rect.y() / scale, rect.width() / scale, rect.height() / scale);
+  return UIAccessibilityConvertFrameToScreenCoordinates(result, [self bridge]->view());
 }
 
 #pragma mark - UIAccessibilityElement protocol