diff --git a/lib/web_ui/lib/src/engine/text/measurement.dart b/lib/web_ui/lib/src/engine/text/measurement.dart index d0c010f951fdaed1a41cfee1fe6df559496b09f2..4ca4f07e2a6d43a8b738d7e51d7f7d7eea7c94a0 100644 --- a/lib/web_ui/lib/src/engine/text/measurement.dart +++ b/lib/web_ui/lib/src/engine/text/measurement.dart @@ -373,7 +373,10 @@ class DomTextMeasurementService extends TextMeasurementService { @override ui.TextPosition getTextPositionForOffset(EngineParagraph paragraph, ui.ParagraphConstraints constraints, ui.Offset offset) { - assert(paragraph._plainText == null, 'should only be called for multispan'); + assert( + paragraph._measurementResult.lines == null, + 'should only be called when the faster lines-based approach is not possible', + ); final ParagraphGeometricStyle style = paragraph._geometricStyle; final ParagraphRuler ruler = diff --git a/lib/web_ui/lib/src/engine/text/paragraph.dart b/lib/web_ui/lib/src/engine/text/paragraph.dart index 67875e812d307efe478b7e864027606bfbe43e0e..dd9b892de1b4a7f2fa40f7254afff00830c39d97 100644 --- a/lib/web_ui/lib/src/engine/text/paragraph.dart +++ b/lib/web_ui/lib/src/engine/text/paragraph.dart @@ -378,17 +378,53 @@ class EngineParagraph implements ui.Paragraph { @override ui.TextPosition getPositionForOffset(ui.Offset offset) { - if (_plainText == null) { + final List lines = _measurementResult.lines; + if (lines == null) { return getPositionForMultiSpanOffset(offset); } + + final int lineNumber = offset.dy ~/ _measurementResult.lineHeight; + + // [offset] is below all the lines. + if (lineNumber >= lines.length) { + return ui.TextPosition( + offset: _plainText.length, + affinity: ui.TextAffinity.upstream, + ); + } + + final EngineLineMetrics lineMetrics = lines[lineNumber]; + final double lineLeft = lineMetrics.left; + final double lineRight = lineLeft + lineMetrics.width; + + // [offset] is to the left of the line. + if (offset.dx <= lineLeft) { + return ui.TextPosition( + offset: lineMetrics.startIndex, + affinity: ui.TextAffinity.downstream, + ); + } + + // [offset] is to the right of the line. + if (offset.dx >= lineRight) { + return ui.TextPosition( + offset: lineMetrics.endIndex, + affinity: ui.TextAffinity.upstream, + ); + } + + // If we reach here, it means the [offset] is somewhere within the line. The + // code below will do a binary search to find where exactly the [offset] + // falls within the line. + final double dx = offset.dx - _alignOffset; final TextMeasurementService instance = _measurementService; - int low = 0; - int high = _plainText.length; + int low = lineMetrics.startIndex; + int high = lineMetrics.endIndex; do { final int current = (low + high) ~/ 2; - final double width = instance.measureSubstringWidth(this, 0, current); + final double width = instance.measureSubstringWidth(this, lineMetrics.startIndex, current); if (width < dx) { low = current; } else if (width > dx) { @@ -403,8 +439,8 @@ class EngineParagraph implements ui.Paragraph { return ui.TextPosition(offset: high, affinity: ui.TextAffinity.upstream); } - final double lowWidth = instance.measureSubstringWidth(this, 0, low); - final double highWidth = instance.measureSubstringWidth(this, 0, high); + final double lowWidth = instance.measureSubstringWidth(this, lineMetrics.startIndex, low); + final double highWidth = instance.measureSubstringWidth(this, lineMetrics.startIndex, high); if (dx - lowWidth < highWidth - dx) { // The offset is closer to the low index. diff --git a/lib/web_ui/test/paragraph_test.dart b/lib/web_ui/test/paragraph_test.dart index 52f34a5afc1a777556b602a63fb66edd95edae00..6fb5ddd5bb51f4d053246f4e393be38803c57535 100644 --- a/lib/web_ui/test/paragraph_test.dart +++ b/lib/web_ui/test/paragraph_test.dart @@ -8,7 +8,7 @@ import 'package:ui/ui.dart'; import 'package:test/test.dart'; void testEachMeasurement(String description, VoidCallback body, {bool skip}) { - test(description, () async { + test('$description (dom measurement)', () async { try { TextMeasurementService.initialize(rulerCacheCapacity: 2); return body(); @@ -130,6 +130,154 @@ void main() async { }, // TODO(nurhan): https://github.com/flutter/flutter/issues/46638 skip: (browserEngine == BrowserEngine.firefox)); + testEachMeasurement('getPositionForOffset single-line', () { + final ParagraphBuilder builder = ParagraphBuilder(ParagraphStyle( + fontFamily: 'Ahem', + fontStyle: FontStyle.normal, + fontWeight: FontWeight.normal, + fontSize: 10, + textDirection: TextDirection.ltr, + )); + builder.addText('abcd efg'); + final Paragraph paragraph = builder.build(); + paragraph.layout(const ParagraphConstraints(width: 1000)); + + // At the beginning of the line. + expect( + paragraph.getPositionForOffset(Offset(0, 5)), + TextPosition(offset: 0, affinity: TextAffinity.downstream), + ); + // Below the line. + expect( + paragraph.getPositionForOffset(Offset(0, 12)), + TextPosition(offset: 8, affinity: TextAffinity.upstream), + ); + // Above the line. + expect( + paragraph.getPositionForOffset(Offset(0, -5)), + TextPosition(offset: 0, affinity: TextAffinity.downstream), + ); + // At the end of the line. + expect( + paragraph.getPositionForOffset(Offset(80, 5)), + TextPosition(offset: 8, affinity: TextAffinity.upstream), + ); + // On the left side of "b". + expect( + paragraph.getPositionForOffset(Offset(14, 5)), + TextPosition(offset: 1, affinity: TextAffinity.downstream), + ); + // On the right side of "b". + expect( + paragraph.getPositionForOffset(Offset(16, 5)), + TextPosition(offset: 2, affinity: TextAffinity.upstream), + ); + }); + + test('getPositionForOffset multi-line', () { + // [Paragraph.getPositionForOffset] for multi-line text doesn't work well + // with dom-based measurement. + TextMeasurementService.enableExperimentalCanvasImplementation = true; + TextMeasurementService.initialize(rulerCacheCapacity: 2); + + final ParagraphBuilder builder = ParagraphBuilder(ParagraphStyle( + fontFamily: 'Ahem', + fontStyle: FontStyle.normal, + fontWeight: FontWeight.normal, + fontSize: 10, + textDirection: TextDirection.ltr, + )); + builder.addText('abcd\n'); + builder.addText('abcdefg\n'); + builder.addText('ab'); + final Paragraph paragraph = builder.build(); + paragraph.layout(const ParagraphConstraints(width: 1000)); + + // First line: "abcd\n" + + // At the beginning of the first line. + expect( + paragraph.getPositionForOffset(Offset(0, 5)), + TextPosition(offset: 0, affinity: TextAffinity.downstream), + ); + // Above the first line. + expect( + paragraph.getPositionForOffset(Offset(0, -5)), + TextPosition(offset: 0, affinity: TextAffinity.downstream), + ); + // At the end of the first line. + expect( + paragraph.getPositionForOffset(Offset(50, 5)), + TextPosition(offset: 5, affinity: TextAffinity.upstream), + ); + // On the left side of "b" in the first line. + expect( + paragraph.getPositionForOffset(Offset(14, 5)), + TextPosition(offset: 1, affinity: TextAffinity.downstream), + ); + // On the right side of "b" in the first line. + expect( + paragraph.getPositionForOffset(Offset(16, 5)), + TextPosition(offset: 2, affinity: TextAffinity.upstream), + ); + + + // Second line: "abcdefg\n" + + // At the beginning of the second line. + expect( + paragraph.getPositionForOffset(Offset(0, 15)), + TextPosition(offset: 5, affinity: TextAffinity.downstream), + ); + // At the end of the second line. + expect( + paragraph.getPositionForOffset(Offset(100, 15)), + TextPosition(offset: 13, affinity: TextAffinity.upstream), + ); + // On the left side of "e" in the second line. + expect( + paragraph.getPositionForOffset(Offset(44, 15)), + TextPosition(offset: 9, affinity: TextAffinity.downstream), + ); + // On the right side of "e" in the second line. + expect( + paragraph.getPositionForOffset(Offset(46, 15)), + TextPosition(offset: 10, affinity: TextAffinity.upstream), + ); + + + // Last (third) line: "ab" + + // At the beginning of the last line. + expect( + paragraph.getPositionForOffset(Offset(0, 25)), + TextPosition(offset: 13, affinity: TextAffinity.downstream), + ); + // At the end of the last line. + expect( + paragraph.getPositionForOffset(Offset(40, 25)), + TextPosition(offset: 15, affinity: TextAffinity.upstream), + ); + // Below the last line. + expect( + paragraph.getPositionForOffset(Offset(0, 32)), + TextPosition(offset: 15, affinity: TextAffinity.upstream), + ); + // On the left side of "b" in the last line. + expect( + paragraph.getPositionForOffset(Offset(12, 25)), + TextPosition(offset: 14, affinity: TextAffinity.downstream), + ); + // On the right side of "a" in the last line. + expect( + paragraph.getPositionForOffset(Offset(9, 25)), + TextPosition(offset: 14, affinity: TextAffinity.upstream), + ); + + TextMeasurementService.clearCache(); + TextMeasurementService.enableExperimentalCanvasImplementation = false; + }); + testEachMeasurement('getBoxesForRange returns a box', () { final ParagraphBuilder builder = ParagraphBuilder(ParagraphStyle( fontFamily: 'Ahem',