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[_ASDisplayViewAccessiblity] Fix accessibility in scroll views (#2079)

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* Fixes issues with accessibility elements in scroll views

There are two changes here:

1. Because we can't reliably update the screen positions of accessibility elements
contained within a scroll view, we need to calculate them on demand, so we override
the accessibilityFrame method to do that.

2. Throwing away our calculated accessibility elements on frame change seemed to
cause the accessibility system to be confused.

Combining these two fixes together results in success, yay!

* Don't set the accessibilityFrame, getter is overridden.
This commit is contained in:
Garrett Moon
2016-08-16 17:01:06 -07:00
committed by Adlai Holler
parent 05dba2263c
commit 7d21ccc184
1 changed files with 24 additions and 18 deletions
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42
AsyncDisplayKit/Details/_ASDisplayViewAccessiblity.mm
View File

@@ -41,11 +41,22 @@ static void SortAccessibilityElements(NSMutableArray *elements)
[elements sortUsingComparator:comparator];
}
@implementation UIAccessibilityElement (_ASDisplayView)
@interface ASAccessibilityElement : UIAccessibilityElement
+ (UIAccessibilityElement *)accessibilityElementWithContainer:(id)container node:(ASDisplayNode *)node
@property (nonatomic, strong) ASDisplayNode *node;
@property (nonatomic, strong) ASDisplayNode *containerNode;
+ (ASAccessibilityElement *)accessibilityElementWithContainer:(UIView *)container node:(ASDisplayNode *)node containerNode:(ASDisplayNode *)containerNode;
@end
@implementation ASAccessibilityElement
+ (ASAccessibilityElement *)accessibilityElementWithContainer:(UIView *)container node:(ASDisplayNode *)node containerNode:(ASDisplayNode *)containerNode
{
UIAccessibilityElement *accessibilityElement = [[UIAccessibilityElement alloc] initWithAccessibilityContainer:container];
ASAccessibilityElement *accessibilityElement = [[ASAccessibilityElement alloc] initWithAccessibilityContainer:container];
accessibilityElement.node = node;
accessibilityElement.containerNode = containerNode;
accessibilityElement.accessibilityIdentifier = node.accessibilityIdentifier;
accessibilityElement.accessibilityLabel = node.accessibilityLabel;
accessibilityElement.accessibilityHint = node.accessibilityHint;
@@ -54,8 +65,14 @@ static void SortAccessibilityElements(NSMutableArray *elements)
return accessibilityElement;
}
@end
- (CGRect)accessibilityFrame
{
CGRect accessibilityFrame = [self.containerNode convertRect:self.node.bounds fromNode:self.node];
accessibilityFrame = UIAccessibilityConvertFrameToScreenCoordinates(accessibilityFrame, self.accessibilityContainer);
return accessibilityFrame;
}
@end
#pragma mark - _ASDisplayView / UIAccessibilityContainer
@@ -68,11 +85,7 @@ static void CollectUIAccessibilityElementsForNode(ASDisplayNode *node, ASDisplay
// For every subnode that is layer backed or it's supernode has shouldRasterizeDescendants enabled
// we have to create a UIAccessibilityElement as no view for this node exists
if (currentNode != containerNode && currentNode.isAccessibilityElement) {
UIAccessibilityElement *accessibilityElement = [UIAccessibilityElement accessibilityElementWithContainer:container node:currentNode];
// As the node hierarchy is flattened it's necessary to convert the frame for each subnode in the tree to the
// coordinate system of the supernode
CGRect frame = [containerNode convertRect:currentNode.bounds fromNode:currentNode];
accessibilityElement.accessibilityFrame = UIAccessibilityConvertFrameToScreenCoordinates(frame, container);
UIAccessibilityElement *accessibilityElement = [ASAccessibilityElement accessibilityElementWithContainer:container node:currentNode containerNode:containerNode];
[elements addObject:accessibilityElement];
}
});
@@ -97,10 +110,7 @@ static void CollectAccessibilityElementsForView(_ASDisplayView *view, NSMutableA
// An accessiblityElement can either be a UIView or a UIAccessibilityElement
if (subnode.isLayerBacked) {
// No view for layer backed nodes exist. It's necessary to create a UIAccessibilityElement that represents this node
UIAccessibilityElement *accessiblityElement = [UIAccessibilityElement accessibilityElementWithContainer:view node:subnode];
CGRect frame = [node convertRect:subnode.bounds fromNode:subnode];
[accessiblityElement setAccessibilityFrame:UIAccessibilityConvertFrameToScreenCoordinates(frame, view)];
UIAccessibilityElement *accessiblityElement = [ASAccessibilityElement accessibilityElementWithContainer:view node:subnode containerNode:node];
[elements addObject:accessiblityElement];
} else {
// Accessiblity element is not layer backed just add the view as accessibility element
@@ -118,7 +128,6 @@ static void CollectAccessibilityElementsForView(_ASDisplayView *view, NSMutableA
@interface _ASDisplayView () {
NSArray *_accessibleElements;
CGRect _lastAccessibleElementsFrame;
}
@end
@@ -139,13 +148,10 @@ static void CollectAccessibilityElementsForView(_ASDisplayView *view, NSMutableA
return @[];
}
CGRect screenFrame = UIAccessibilityConvertFrameToScreenCoordinates(self.bounds, self);
if (_accessibleElements != nil && CGRectEqualToRect(_lastAccessibleElementsFrame, screenFrame)) {
if (_accessibleElements != nil) {
return _accessibleElements;
}
_lastAccessibleElementsFrame = screenFrame;
NSMutableArray *accessibleElements = [NSMutableArray array];
CollectAccessibilityElementsForView(self, accessibleElements);
SortAccessibilityElements(accessibleElements);