Add support for basic ASTextNode2 link highlighting (#1518)

* Add support for basic ASTextNode2 link highlighting

* Add approach to fix line highlighting

* Enable proper highlighting for first row

* Fix snapshot highlighting test for ASTextNode2

* Update screenshot again

* Address comments

Source/ASTextNode.mm

@@ -766,6 +766,7 @@ static NSArray *DefaultLinkAttributeNames() {
 - (void)_setHighlightRange:(NSRange)highlightRange forAttributeName:(NSString *)highlightedAttributeName value:(id)highlightedAttributeValue animated:(BOOL)animated
 {
   ASDisplayNodeAssertMainThread();
+  ASLockScopeSelf();
 
   _highlightedLinkAttributeName = highlightedAttributeName;
   _highlightedLinkAttributeValue = highlightedAttributeValue;
@@ -825,7 +826,6 @@ static NSArray *DefaultLinkAttributeNames() {
       }
 
       if (highlightTargetLayer != nil) {
-        ASLockScopeSelf();
         ASTextKitRenderer *renderer = [self _locked_renderer];
 
         NSArray *highlightRects = [renderer rectsForTextRange:highlightRange measureOption:ASTextKitRendererMeasureOptionBlock];

Source/ASTextNode2.mm

@@ -137,6 +137,8 @@ static NS_RETURNS_RETAINED ASTextLayout *ASTextNodeCompatibleLayoutWithContainer
   return layout;
 }
 
+static const NSTimeInterval ASTextNodeHighlightFadeOutDuration = 0.15;
+static const NSTimeInterval ASTextNodeHighlightFadeInDuration = 0.1;
 static const CGFloat ASTextNodeHighlightLightOpacity = 0.11;
 static const CGFloat ASTextNodeHighlightDarkOpacity = 0.22;
 static NSString *ASTextNodeTruncationTokenAttributeName = @"ASTextNodeTruncationAttribute";
@@ -778,17 +780,114 @@ static NSArray *DefaultLinkAttributeNames() {
 
 - (void)_setHighlightRange:(NSRange)highlightRange forAttributeName:(NSString *)highlightedAttributeName value:(id)highlightedAttributeValue animated:(BOOL)animated
 {
+  ASDisplayNodeAssertMainThread();
   ASLockScopeSelf(); // Protect usage of _highlight* ivars.
 
   // Set these so that link tapping works.
   _highlightedLinkAttributeName = highlightedAttributeName;
   _highlightedLinkAttributeValue = highlightedAttributeValue;
-  _highlightRange = highlightRange;
 
-  AS_TEXT_ALERT_UNIMPLEMENTED_FEATURE();
-  // Much of the code from original ASTextNode is probably usable here.
+  if (!NSEqualRanges(highlightRange, _highlightRange) && ((0 != highlightRange.length) || (0 != _highlightRange.length))) {
 
-  return;
+    _highlightRange = highlightRange;
+
+    if (_activeHighlightLayer) {
+      if (animated) {
+        __weak CALayer *weakHighlightLayer = _activeHighlightLayer;
+        _activeHighlightLayer = nil;
+
+        weakHighlightLayer.opacity = 0.0;
+
+        CFTimeInterval beginTime = CACurrentMediaTime();
+        CABasicAnimation *possibleFadeIn = (CABasicAnimation *)[weakHighlightLayer animationForKey:@"opacity"];
+        if (possibleFadeIn) {
+          // Calculate when we should begin fading out based on the end of the fade in animation,
+          // Also check to make sure that the new begin time hasn't already passed
+          CGFloat newBeginTime = (possibleFadeIn.beginTime + possibleFadeIn.duration);
+          if (newBeginTime > beginTime) {
+            beginTime = newBeginTime;
+          }
+        }
+
+        CABasicAnimation *fadeOut = [CABasicAnimation animationWithKeyPath:@"opacity"];
+        fadeOut.timingFunction = [CAMediaTimingFunction functionWithName:kCAMediaTimingFunctionEaseInEaseOut];
+        fadeOut.fromValue = possibleFadeIn.toValue ? : @(((CALayer *)weakHighlightLayer.presentationLayer).opacity);
+        fadeOut.toValue = @0.0;
+        fadeOut.fillMode = kCAFillModeBoth;
+        fadeOut.duration = ASTextNodeHighlightFadeOutDuration;
+        fadeOut.beginTime = beginTime;
+
+        dispatch_block_t prev = [CATransaction completionBlock];
+        [CATransaction setCompletionBlock:^{
+          [weakHighlightLayer removeFromSuperlayer];
+        }];
+
+        [weakHighlightLayer addAnimation:fadeOut forKey:fadeOut.keyPath];
+
+        [CATransaction setCompletionBlock:prev];
+
+      } else {
+        [_activeHighlightLayer removeFromSuperlayer];
+        _activeHighlightLayer = nil;
+      }
+    }
+    if (0 != highlightRange.length) {
+      // Find layer in hierarchy that allows us to draw highlighting on.
+      CALayer *highlightTargetLayer = self.layer;
+      while (highlightTargetLayer != nil) {
+        if (highlightTargetLayer.as_allowsHighlightDrawing) {
+          break;
+        }
+        highlightTargetLayer = highlightTargetLayer.superlayer;
+      }
+
+      if (highlightTargetLayer != nil) {
+        // TODO: The copy and application of size shouldn't be required, but it is currently.
+        // See discussion in https://github.com/TextureGroup/Texture/pull/396
+        ASTextContainer *textContainerCopy = [_textContainer copy];
+        textContainerCopy.size = self.calculatedSize;
+        ASTextLayout *layout = ASTextNodeCompatibleLayoutWithContainerAndText(textContainerCopy, _attributedText);
+
+        NSArray<ASTextSelectionRect *> *highlightRects = [layout selectionRectsWithoutStartAndEndForRange:[ASTextRange rangeWithRange:highlightRange]];
+        NSMutableArray *converted = [NSMutableArray arrayWithCapacity:highlightRects.count];
+
+        CALayer *layer = self.layer;
+        UIEdgeInsets shadowPadding = self.shadowPadding;
+        for (ASTextSelectionRect *rectValue in highlightRects) {
+          // Adjust shadow padding
+          CGRect rendererRect = ASTextNodeAdjustRenderRectForShadowPadding(rectValue.rect, shadowPadding);
+          CGRect highlightedRect = [layer convertRect:rendererRect toLayer:highlightTargetLayer];
+
+          // We set our overlay layer's frame to the bounds of the highlight target layer.
+          // Offset highlight rects to avoid double-counting target layer's bounds.origin.
+          highlightedRect.origin.x -= highlightTargetLayer.bounds.origin.x;
+          highlightedRect.origin.y -= highlightTargetLayer.bounds.origin.y;
+          [converted addObject:[NSValue valueWithCGRect:highlightedRect]];
+        }
+
+        ASHighlightOverlayLayer *overlayLayer = [[ASHighlightOverlayLayer alloc] initWithRects:converted];
+        overlayLayer.highlightColor = [[self class] _highlightColorForStyle:self.highlightStyle];
+        overlayLayer.frame = highlightTargetLayer.bounds;
+        overlayLayer.masksToBounds = NO;
+        overlayLayer.opacity = [[self class] _highlightOpacityForStyle:self.highlightStyle];
+        [highlightTargetLayer addSublayer:overlayLayer];
+
+        if (animated) {
+          CABasicAnimation *fadeIn = [CABasicAnimation animationWithKeyPath:@"opacity"];
+          fadeIn.fromValue = @0.0;
+          fadeIn.toValue = @(overlayLayer.opacity);
+          fadeIn.duration = ASTextNodeHighlightFadeInDuration;
+          fadeIn.beginTime = CACurrentMediaTime();
+
+          [overlayLayer addAnimation:fadeIn forKey:fadeIn.keyPath];
+        }
+
+        [overlayLayer setNeedsDisplay];
+
+        _activeHighlightLayer = overlayLayer;
+      }
+    }
+  }
 }
 
 - (void)_clearHighlightIfNecessary
@@ -812,6 +911,12 @@ static NSArray *DefaultLinkAttributeNames() {
 
 #pragma mark - Text rects
 
+static CGRect ASTextNodeAdjustRenderRectForShadowPadding(CGRect rendererRect, UIEdgeInsets shadowPadding) {
+  rendererRect.origin.x -= shadowPadding.left;
+  rendererRect.origin.y -= shadowPadding.top;
+  return rendererRect;
+}
+
 - (NSArray *)rectsForTextRange:(NSRange)textRange
 {
   AS_TEXT_ALERT_UNIMPLEMENTED_FEATURE();

Source/Private/TextExperiment/Component/ASTextLayout.mm

@@ -2146,7 +2146,9 @@ dispatch_semaphore_signal(_lock);
       if (isVertical) {
         topRect.rect = CGRectMake(startLine.left, topOffset, startLine.width, (_container.path ? startLine.bottom : _container.size.height - _container.insets.bottom) - topOffset);
       } else {
-        topRect.rect = CGRectMake(topOffset, startLine.top, (_container.path ? startLine.right : _container.size.width - _container.insets.right) - topOffset, startLine.height);
+        // TODO: Fixes highlighting first row only to the end of the text and not highlight
+        //       the while line to the end. Needs to brought over to multiline support
+        topRect.rect = CGRectMake(topOffset, startLine.top, (_container.path ? startLine.right : _container.size.width - _container.insets.right) - topOffset - (_container.size.width - _container.insets.right - startLine.right), startLine.height);
       }
     }
     [rects addObject:topRect];