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Right aligned backspace bug #25229

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Merged
justinmc merged 7 commits into from
Dec 20, 2018
Merged

Right aligned backspace bug #25229

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978638f
Fix bug in calculation of downstream text distance when aligned: right
justinmc Dec 11, 2018
ee05613
After having affinity explained to me, match getOffset and tests to
justinmc Dec 12, 2018
73a3110
Clean up test formatting and fix analyze errors
justinmc Dec 14, 2018
e249b9c
Improve test comments and reorganize a bit
justinmc Dec 17, 2018
4937647
Merge branch 'master' into text-field-right-backspace
justinmc Dec 18, 2018
bbb2713
Specify logical pixels
justinmc Dec 19, 2018
85617ff
Merge branch 'master' into text-field-right-backspace
justinmc Dec 19, 2018
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12 changes: 12 additions & 0 deletions packages/flutter/lib/src/painting/text_painter.dart
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Original file line number Diff line number Diff line change
Expand Up @@ -417,13 +417,16 @@ class TextPainter {
// Unicode value for a zero width joiner character.
static const int _zwjUtf16 = 0x200d;

// Get the Offset of the cursor (in logical pixels) based off the near edge
// of the character upstream from the given string offset.
// TODO(garyq): Use actual extended grapheme cluster length instead of
// an increasing cluster length amount to achieve deterministic performance.
Offset _getOffsetFromUpstream(int offset, Rect caretPrototype) {
final String flattenedText = _text.toPlainText();
final int prevCodeUnit = _text.codeUnitAt(max(0, offset - 1));
if (prevCodeUnit == null)
return null;

// Check for multi-code-unit glyphs such as emojis or zero width joiner
final bool needsSearch = _isUtf16Surrogate(prevCodeUnit) || _text.codeUnitAt(offset) == _zwjUtf16;
int graphemeClusterLength = needsSearch ? 2 : 1;
Expand All @@ -447,13 +450,22 @@ class TextPainter {
continue;
}
final TextBox box = boxes.first;

// If the upstream character is a newline, cursor is at start of next line
const int NEWLINE_CODE_UNIT = 10;
if (prevCodeUnit == NEWLINE_CODE_UNIT) {
return Offset(_emptyOffset.dx, box.bottom);
}

final double caretEnd = box.end;
final double dx = box.direction == TextDirection.rtl ? caretEnd - caretPrototype.width : caretEnd;
return Offset(dx, box.top);
}
return null;
}

// Get the Offset of the cursor (in logical pixels) based off the near edge
// of the character downstream from the given string offset.
// TODO(garyq): Use actual extended grapheme cluster length instead of
// an increasing cluster length amount to achieve deterministic performance.
Offset _getOffsetFromDownstream(int offset, Rect caretPrototype) {
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