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Draw text with unbounded height on iOS (#59793) #59793

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Merged
meta-codesync merged 1 commit into from
Nov 6, 2026
+15 −3
Merged

Draw text with unbounded height on iOS (#59793) #59793

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18 changes: 15 additions & 3 deletions ...r/textlayoutmanager/platform/ios/react/renderer/textlayoutmanager/RCTTextLayoutManager.mm
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Original file line number Diff line number Diff line change
Expand Up @@ -39,6 +39,18 @@ static NSLineBreakMode RCTNSLineBreakModeFromEllipsizeMode(EllipsizeMode ellipsi
}
}

// Text is laid out with an unbounded height, as during measurement, so that lines and attachments end up where
// measurement placed them. A container clamped to the frame height makes TextKit squeeze the remaining content into
// the last line that fits. The paragraph view clips the drawing to its bounds.
static CGSize RCTTextLayoutSizeForFrameSize(CGSize frameSize, const ParagraphAttributes &paragraphAttributes)
{
if (paragraphAttributes.adjustsFontSizeToFit) {
// Font scaling shrinks the text until it fits the frame height.
return frameSize;
}
return CGSize{frameSize.width, CGFLOAT_MAX};
}

- (TextMeasurement)measureNSAttributedString:(NSAttributedString *)attributedString
paragraphAttributes:(ParagraphAttributes)paragraphAttributes
layoutContext:(TextLayoutContext)layoutContext
Expand Down Expand Up @@ -136,7 +148,7 @@ - (void)drawAttributedString:(const AttributedString &)attributedString
NSTextStorage *textStorage = [self
_textStorageAndLayoutManagerWithAttributesString:[self _nsAttributedStringFromAttributedString:attributedString]
paragraphAttributes:paragraphAttributes
size:frame.size];
size:RCTTextLayoutSizeForFrameSize(frame.size, paragraphAttributes)];
NSLayoutManager *layoutManager = textStorage.layoutManagers.firstObject;
NSTextContainer *textContainer = layoutManager.textContainers.firstObject;

Expand Down Expand Up @@ -475,7 +487,7 @@ - (NSTextStorage *)_textStorageAndLayoutManagerWithAttributesString:(NSAttribute
NSTextStorage *textStorage = [self
_textStorageAndLayoutManagerWithAttributesString:[self _nsAttributedStringFromAttributedString:attributedString]
paragraphAttributes:paragraphAttributes
size:frame.size];
size:RCTTextLayoutSizeForFrameSize(frame.size, paragraphAttributes)];
NSLayoutManager *layoutManager = textStorage.layoutManagers.firstObject;
NSTextContainer *textContainer = layoutManager.textContainers.firstObject;

Expand Down Expand Up @@ -506,7 +518,7 @@ - (void)getRectWithAttributedString:(const AttributedString &)attributedString
NSTextStorage *textStorage = [self
_textStorageAndLayoutManagerWithAttributesString:[self _nsAttributedStringFromAttributedString:attributedString]
paragraphAttributes:paragraphAttributes
size:frame.size];
size:RCTTextLayoutSizeForFrameSize(frame.size, paragraphAttributes)];

NSLayoutManager *layoutManager = textStorage.layoutManagers.firstObject;
NSTextContainer *textContainer = layoutManager.textContainers.firstObject;
Expand Down
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