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Skip redrawing iOS Text when only its position changes #59155

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Skip redrawing iOS Text when only its position changes #59155

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37 changes: 34 additions & 3 deletions packages/react-native/React/Fabric/Mounting/ComponentViews/Text/RCTParagraphComponentView.mm
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Original file line number Diff line number Diff line change
Expand Up @@ -34,6 +34,16 @@ - (CGRect)drawingFrameForAttributedString:(const facebook::react::AttributedStri

@end

static BOOL RCTAttributedStringHasAttachments(const AttributedString &attributedString)
{
for (const auto &fragment : attributedString.getFragments()) {
if (fragment.isAttachment()) {
return YES;
}
}
return NO;
}

// ParagraphTextView is an auxiliary view we set as contentView so the drawing
// can happen on top of the layers manipulated by RCTViewComponentView (the parent view)
@interface RCTParagraphTextView : UIView
Expand Down Expand Up @@ -135,8 +145,22 @@ - (void)updateProps:(const Props::Shared &)props oldProps:(const Props::Shared &

- (void)updateState:(const State::Shared &)state oldState:(const State::Shared &)oldState
{
_textView.state = std::static_pointer_cast<const ParagraphShadowNode::ConcreteState>(state);
[_textView setNeedsDisplay];
auto newState = std::static_pointer_cast<const ParagraphShadowNode::ConcreteState>(state);
// A relayout yields a new state even for unchanged text (the attributed
// string records fragment layout metrics); redraw only when content or
// paragraph attributes changed. Attachments are sized from those metrics.
BOOL needsDisplay = YES;
if (newState && oldState && _textView.state) {
const auto &newData = newState->getData();
const auto &oldData = std::static_pointer_cast<const ParagraphShadowNode::ConcreteState>(oldState)->getData();
needsDisplay = !newData.attributedString.isContentEqual(oldData.attributedString) ||
newData.paragraphAttributes != oldData.paragraphAttributes ||
RCTAttributedStringHasAttachments(newData.attributedString);
}
_textView.state = newState;
if (needsDisplay) {
[_textView setNeedsDisplay];
}

// If the attributed string has changed, we need to notify the accessibility system that something changed,
// otherwise it may hold on to stale values (this happens most often when an element is updated async)
Expand All @@ -161,11 +185,18 @@ - (void)updateState:(const State::Shared &)state oldState:(const State::Shared &
- (void)updateLayoutMetrics:(const LayoutMetrics &)layoutMetrics
oldLayoutMetrics:(const LayoutMetrics &)oldLayoutMetrics
{
// Drawing depends on size, content frame and scale, not on position.
BOOL needsDisplay = _layoutMetrics.frame.size != layoutMetrics.frame.size ||
_layoutMetrics.getContentFrame() != layoutMetrics.getContentFrame() ||
_layoutMetrics.pointScaleFactor != layoutMetrics.pointScaleFactor;

// Using stored `_layoutMetrics` as `oldLayoutMetrics` here to avoid
// re-applying individual sub-values which weren't changed.
[super updateLayoutMetrics:layoutMetrics oldLayoutMetrics:_layoutMetrics];
_textView.layoutMetrics = _layoutMetrics;
[_textView setNeedsDisplay];
if (needsDisplay) {
[_textView setNeedsDisplay];
}
}

- (void)finalizeUpdates:(RNComponentViewUpdateMask)updateMask
Expand Down
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