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New TextBreakIterator's default behavior breaks after space run
Before this change, we were considering breaking opportunities before space runs. This approach allowed us to avoid re-shaping in many cases, which has an important advantage in terms of performance. However, the Unicode spec (UAX#14) state that breaking before a space character is not allowed [1], so we had to implement this logic after our TextBreakIterator had already determined the best breaking opportunity. This approach has been working fine so far for regular spaces (white-space, tabs, ...), but it doesn't work correctly for other BA [2] class characters; in the CSS Text specification, these are known as "other space separators" [3]. In order to implement the correct behavior for any kind of space, we would need to change our TextBreakIterator implementation so that matches the Unicode rules, considering breaking opportunity after space runs. This change should also consider the performance impact of the extra re-shaping operations required to deal with trailing spaces. In order to prevent performance regressions, we'll store the position of the 'end of non-hangable run', which will be used in case of items with styles dictating rules to collapse trailing spaces. [1] https://unicode-org.atlassian.net/browse/ICU-20843 [2] https://www.unicode.org/reports/tr14/tr14-39.html#BA [3] https://drafts.csswg.org/css-text-3/#other-space-separators Change-Id: Ie4a3890c75a3faff1a0155d4a40bcaa85bc6ac06
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css/css-text/white-space/reference/white-space-pre-wrap-trailing-spaces-013-ref.html
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,13 @@ | ||
| <!doctype html> | ||
| <meta charset=utf-8> | ||
| <meta http-equiv="content-language" content="en, ja" /> | ||
| <title>CSS test Reference</title> | ||
| <link rel="author" title="Javier Fernandez" href="mailto:jfernandez@igalia.com" /> | ||
| <style> | ||
| div { white-space: pre; } | ||
| span { background: blue; } | ||
| </style> | ||
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| <p>This test passes if the line is after the white space, which hangs (blue). | ||
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| <div>ああ<span> <br>X</span></div> |
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css/css-text/white-space/white-space-pre-wrap-trailing-spaces-012.html
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,35 @@ | ||
| <!doctype html> | ||
| <meta charset=utf-8> | ||
| <title>CSS Text test: hanging trailing spaces with white-space:pre-wrap</title> | ||
| <link rel="author" title="Javier Fernandez" href="mailto:jfernandez@igalia.com"> | ||
| <link rel="help" title="3. White Space and Wrapping: the white-space property" href="https://drafts.csswg.org/css-text-3/#white-space-property"> | ||
| <link rel="help" href="https://drafts.csswg.org/css-text-3/#valdef-white-space-pre-wrap"> | ||
| <link rel="help" title="4.1.3. Phase II: Trimming and Positioning" href="https://drafts.csswg.org/css-text-3/#white-space-phase-2"> | ||
| <link rel="help" title="5.2. Breaking Rules for Letters: the word-break property" href="https://drafts.csswg.org/css-text-3/#word-break-property"> | ||
| <link rel="help" href="https://drafts.csswg.org/css-text-3/#valdef-word-break-normal"> | ||
| <link rel="match" href="reference/white-space-pre-wrap-trailing-spaces-004-ref.html"> | ||
| <meta name="assert" content="Previous breaking opportunities are not considered if the overflow is caused by hanging trailing spaces."> | ||
| <link rel="stylesheet" type="text/css" href="/fonts/ahem.css"> | ||
| <style> | ||
| div { | ||
| font: 10px/1 Ahem; | ||
| } | ||
| .ref { | ||
| position: absolute; | ||
| color: red; | ||
| z-index: -1; | ||
| } | ||
| .ref span { color: green; } | ||
| span { background: green; } | ||
| .test { | ||
| color: green; | ||
|
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| width: 4ch; | ||
| white-space: pre-wrap; | ||
| } | ||
| </style> | ||
|
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| <p>This test passes if there is a green square and no red. | ||
| <div class="ref">XX<span>X</span>XX<br>XXXXX</span><br>XXXXX<br>XXXXX<br>XXXXX</div> | ||
| <div class="test">XX X<span> X</span><span>XX </span>XXXXX<br>XXXXX<br>XXXXX</div> | ||
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css/css-text/white-space/white-space-pre-wrap-trailing-spaces-013.html
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,24 @@ | ||
| <!doctype html> | ||
| <meta charset=utf-8> | ||
| <meta http-equiv="content-language" content="en, ja" /> | ||
| <title>CSS Text test: hanging trailing spaces with white-space:pre-wrap</title> | ||
| <link rel="author" title="Javier Fernandez" href="mailto:jfernandez@igalia.com"> | ||
| <link rel="help" title="3. White Space and Wrapping: the white-space property" href="https://drafts.csswg.org/css-text-3/#white-space-property"> | ||
| <link rel="help" href="https://drafts.csswg.org/css-text-3/#valdef-white-space-pre-wrap"> | ||
| <link rel="help" title="4.1.3. Phase II: Trimming and Positioning" href="https://drafts.csswg.org/css-text-3/#white-space-phase-2"> | ||
| <link rel="help" title="5.2. Breaking Rules for Letters: the word-break property" href="https://drafts.csswg.org/css-text-3/#word-break-property"> | ||
| <link rel="help" href="https://drafts.csswg.org/css-text-3/#valdef-word-break-normal"> | ||
| <link rel="match" href="reference/white-space-pre-wrap-trailing-spaces-013-ref.html"> | ||
| <meta name="assert" content="Previous breaking opportunities are not considered if the overflow is caused by hanging trailing spaces."> | ||
| <style> | ||
| div { | ||
| width: 2em; | ||
| white-space: pre-wrap; | ||
| } | ||
| span { background: blue; } /* If the space is removed instead of hanging, there will be no blue box*/ | ||
| </style> | ||
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| <p>This test passes if the line is after the white space, which hangs (blue). | ||
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| <div>ああ<span> X<span></div> | ||
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css/css-text/white-space/white-space-pre-wrap-trailing-spaces-014.html
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,35 @@ | ||
| <!doctype html> | ||
| <meta charset=utf-8> | ||
| <title>CSS Text test: hanging trailing spaces with white-space:pre-wrap</title> | ||
| <link rel="author" title="Javier Fernandez" href="mailto:jfernandez@igalia.com"> | ||
| <link rel="help" title="3. White Space and Wrapping: the white-space property" href="https://drafts.csswg.org/css-text-3/#white-space-property"> | ||
| <link rel="help" href="https://drafts.csswg.org/css-text-3/#valdef-white-space-pre-wrap"> | ||
| <link rel="help" title="4.1.3. Phase II: Trimming and Positioning" href="https://drafts.csswg.org/css-text-3/#white-space-phase-2"> | ||
| <link rel="help" title="5.2. Breaking Rules for Letters: the word-break property" href="https://drafts.csswg.org/css-text-3/#word-break-property"> | ||
| <link rel="help" href="https://drafts.csswg.org/css-text-3/#valdef-word-break-normal"> | ||
| <link rel="match" href="reference/white-space-pre-wrap-trailing-spaces-004-ref.html"> | ||
| <meta name="assert" content="Previous breaking opportunities are not considered if the overflow is caused by hanging trailing spaces."> | ||
| <link rel="stylesheet" type="text/css" href="/fonts/ahem.css"> | ||
| <style> | ||
| div { | ||
| font: 10px/1 Ahem; | ||
| } | ||
| .ref { | ||
| position: absolute; | ||
| color: red; | ||
| z-index: -1; | ||
| } | ||
| span { background: green; } | ||
| .ref span { color: green; } | ||
| .test { | ||
| color: green; | ||
|
|
||
| width: 4ch; | ||
| white-space: pre-wrap; | ||
| } | ||
| </style> | ||
|
|
||
| <p>This test passes if there is a green square and no red. | ||
| <div class="ref">XX<span>X</span>X<span>X</span><br>XXXXX</span><br>XXXXX<br>XXXXX<br>XXXXX</div> | ||
| <div class="test">XX<span> X</span> X<span>XX </span>XXXXX<br>XXXXX<br>XXXXX</div> | ||
|
|
35 changes: 35 additions & 0 deletions
35
css/css-text/white-space/white-space-pre-wrap-trailing-spaces-015.html
This file contains bidirectional Unicode text that may be interpreted or compiled differently than what appears below. To review, open the file in an editor that reveals hidden Unicode characters.
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,35 @@ | ||
| <!doctype html> | ||
| <meta charset=utf-8> | ||
| <title>CSS Text test: hanging trailing spaces with white-space:pre-wrap</title> | ||
| <link rel="author" title="Javier Fernandez" href="mailto:jfernandez@igalia.com"> | ||
| <link rel="help" title="3. White Space and Wrapping: the white-space property" href="https://drafts.csswg.org/css-text-3/#white-space-property"> | ||
| <link rel="help" href="https://drafts.csswg.org/css-text-3/#valdef-white-space-pre-wrap"> | ||
| <link rel="help" title="4.1.3. Phase II: Trimming and Positioning" href="https://drafts.csswg.org/css-text-3/#white-space-phase-2"> | ||
| <link rel="help" title="5.2. Breaking Rules for Letters: the word-break property" href="https://drafts.csswg.org/css-text-3/#word-break-property"> | ||
| <link rel="help" href="https://drafts.csswg.org/css-text-3/#valdef-word-break-normal"> | ||
| <link rel="match" href="reference/white-space-pre-wrap-trailing-spaces-004-ref.html"> | ||
| <meta name="assert" content="Previous breaking opportunities are not considered if the overflow is caused by hanging trailing spaces."> | ||
| <link rel="stylesheet" type="text/css" href="/fonts/ahem.css"> | ||
| <style> | ||
| div { | ||
| font: 10px/1 Ahem; | ||
| } | ||
| .ref { | ||
| position: absolute; | ||
| color: red; | ||
| z-index: -1; | ||
| } | ||
| span { background: green; } | ||
| .ref span { color: green; } | ||
| .test { | ||
| color: green; | ||
|
|
||
| width: 5ch; | ||
| white-space: pre-wrap; | ||
| } | ||
| </style> | ||
|
|
||
| <p>This test passes if there is a green square and no red. | ||
| <div class="ref">XX<span>XXX</span><br>XXX<span>X</span>X<br>XXXXX</span><br>XXXXX<br>XXXXX<br></div> | ||
| <div class="test">XX XX<span>X X</span><br>XXXXX<br>XXXXX<br>XXXXX</div> | ||
|
|
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