charted/lib/core/text_metrics.dart - Issue 1400473008: Roll Observatory packages and add a roll script

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Issue 1400473008: Roll Observatory packages and add a roll script (Closed) Base URL: git@github.com:dart-lang/observatory_pub_packages.git@master

Patch Set: Created 5 years, 2 months ago

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1 //

2 // Copyright 2014 Google Inc. All rights reserved.

3 //

4 // Use of this source code is governed by a BSD-style

5 // license that can be found in the LICENSE file or at

6 // https://developers.google.com/open-source/licenses/bsd

7 //

8

9 /// Provides a way to measure rendered text width for clipping

10 /// text on tooltips and ticks when they are too long.

11 library charted.core.text_metrics;

12

13 import "dart:html";

14 import "package:charted/core/text_metrics/segmentation.dart";

15

16 /// Utilities to measure text width.

17 class TextMetrics {

18 static CanvasElement canvas;

19 static CanvasRenderingContext2D context;

20 static TextMetrics instance;

21

22 static const MAX_STRING_LENGTH = 250;

23 static final FONT_SIZE_REGEX = new RegExp("\s?([0-9]+)px\s?");

24

25 final String fontStyle;

26 int fontSize = 16;

27

28 String currentFontStyle;

29

30 factory TextMetrics({String fontStyle}) {

31 if (canvas == null \|\| context == null) {

32 canvas = document.createElement('canvas');

33 context = canvas.getContext('2d');

34 }

35 if (instance == null) {

36 instance = new TextMetrics._internal(fontStyle);

37 }

38 return instance;

39 }

40 TextMetrics._internal(this.fontStyle) {

41 Match match = FONT_SIZE_REGEX.firstMatch(fontStyle);

42 fontSize = int.parse(match.group(1));

43 }

44

45 void setFontStyle(String fontStyle) {

46 if (fontStyle == null) {

47 fontStyle = this.fontStyle;

48 }

49 if (currentFontStyle != fontStyle) {

50 context.font = fontStyle;

51 currentFontStyle = fontStyle;

52 }

53 }

54

55 /// Measure width of [text] in pixels.

56 /// Optionally, uses [fontStyle] instead of using the default style

57 double getTextWidth(String text, {String fontStyle}) {

58 assert(text.length <= MAX_STRING_LENGTH);

59 setFontStyle(fontStyle);

60 return context.measureText(text).width;

61 }

62

63 /// Gets length of the longest string in the given [strings].

64 /// Optionally, uses [fontStyle] instead of using the default style.

65 double getLongestTextWidth(Iterable<String> strings, {String fontStyle}) {

66 setFontStyle(fontStyle);

67 double maxWidth = 0.0;

68 for (int i = 0; i < strings.length; ++i) {

69 assert(strings.elementAt(i).length <= MAX_STRING_LENGTH);

70 double width = context.measureText(strings.elementAt(i)).width;

71 if (width > maxWidth) {

72 maxWidth = width;

73 }

74 }

75

76 return maxWidth;

77 }

78

79 /// Truncates given [text] to fit in [width]. Adds an ellipsis to the

80 /// returned string, if it needed to be truncated.

81 /// Optionally, uses [fontStyle] instead of using the default style.

82 String ellipsizeText(String text, double width, {String fontStyle}) {

83 assert(text.length <= MAX_STRING_LENGTH);

84 setFontStyle(fontStyle);

85 double computedWidth = context.measureText(text).width;

86 if (computedWidth > width) {

87 var indices = graphemeBreakIndices(text);

88 var position = 0,

89 min = 0, max = indices.length - 1, mid,

90 ellipsis = context.measureText('…').width;

91 width = width - ellipsis;

92 while (max >= min) {

93 mid = (min + max) ~/ 2;

94 position = indices[mid];

95 if (context.measureText(text.substring(0, position)).width > width) {

96 max = mid - 1;

97 } else {

98 min = mid + 1;

99 }

100 }

101 text = text.substring(0, indices[max]) + '…';

102 }

103 return text;

104 }

105

106 /// Truncates text in the given [element], which is either a [SvgTextElement]

107 /// or a [SvgTspanElement] to fit in [width]. Appends an ellipsis to the text

108 /// if it had to be truncated.

109 /// Calling this method may force a layout on the document. For better

110 /// performance, use [TextMetrics.ellipsizeText].

111 static ellipsizeTextElement() {

112 }

113 }

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