- From: therahedwig via GitHub <sysbot+gh@w3.org>
- Date: Sun, 30 Oct 2022 13:32:17 +0000
- To: public-svg-issues@w3.org
therahedwig has just created a new issue for https://github.com/w3c/svgwg:
== Some suggested textLength algorithm adjustments. ==
When implementing the textLength algorithm, I found it had problems with right-to-left text, but unlike my other problems, I actually managed to find a solution to these, which are twofold:
1. For RTL text, it is important that the textLength shift is applied in the 'visual' post-bidi algorithm order instead of the logical one. Otherwise it will look as if the shift is happening in the opposite direction.
2. For nested textLength, all characters that follow a textLength span but are still in the same text chunk should be adjusted with shift as well, otherwise they'll overlap. This affects LTR text too.
3. Combining the above two, you will need to, after doing the adjustments inside the textLength span in visual order, look forward (or backward for RTL), note down all logical characters and their visual indices until you find the end of the text chunk. Then, in visual order, adjust the shift of each result as long as the visual index is above the highest visual index that is part of the textLength span.
This should give the most complete results, though it will require knowing the visual index in addition to the logical one.
(The XO's are a test-font)
```
<svg width="355px" height="210px"
xmlns="http://www.w3.org/2000/svg" version="2.0">
<g id="testRect" >
<rect stroke="red" fill="none" x="255" y="5" width="95" height="200" />
<rect stroke="red" fill="none" x="5" y="5" width="250" height="200" />
<text id="test1" x="5" y="20"
font-family="DejaVu Sans" font-size="15"
fill="blue"
textLength="250">Lorem ipsum dolor sit amet</text>
<text id="test2" x="5" y="40"
font-family="DejaVu Sans" font-size="15"
fill="cyan"
textLength="250">Lorem ipsum dolor sit amet<tspan x="5" y="55">Lorem ipsum dolor sit amet</tspan></text>
<text id="test3" x="155" y="40"
font-family="DejaVu Sans" font-size="15"
fill="green"
textLength="100">Lorem ipsum dolor sit amet</text>
<text id="test4" x="155" y="55"
font-family="DejaVu Sans" font-size="15"
fill="lightgreen"
textLength="100"
lengthAdjust="spacingAndGlyphs">Lorem ipsum dolor sit amet</text>
<text id="test5" x="5" y="70"
font-family="DejaVu Sans" font-size="15"
fill="magenta"
textLength="250"
lengthAdjust="spacingAndGlyphs">Lorem ipsum dolor sit amet</text>
<text id="test6" x="5" y="85"
font-family="DejaVu Sans" font-size="15"
fill="orange"
textLength="250">Lorem ipsum <tspan textLength="100">dolor</tspan> sit amet</text>
<text id="test7" x="5" y="100"
font-family="DejaVu Sans" font-size="15"
fill="purple"
lengthAdjust="spacingAndGlyphs"
textLength="250">Lorem ipsum <tspan textLength="100" lengthAdjust="spacingAndGlyphs">dolor</tspan> sit amet</text>
<text id="test1rtl" x="255" y="120"
font-family="DejaVu Sans" font-size="15"
fill="blue"
direction="rtl"
textLength="250">اللغة العربية المعيارية الحديثة</text>
<text id="test2rtl" x="255" y="140"
font-family="DejaVu Sans" font-size="15"
fill="cyan"
direction="rtl"
textLength="250">اللغة العربية المعيارية الحديثة<tspan x="255" y="155">اللغة العربية المعيارية الحديثة </tspan></text>
<text id="test3rtl" x="105" y="140"
font-family="DejaVu Sans" font-size="15"
fill="green"
direction="rtl"
textLength="100">اللغة العربية المعيارية الحديثة</text>
<text id="test4rtl" x="105" y="155"
font-family="DejaVu Sans" font-size="15"
fill="lightgreen"
direction="rtl"
textLength="100"
lengthAdjust="spacingAndGlyphs">اللغة العربية المعيارية الحديثة</text>
<text id="test5rtl" x="255" y="170"
font-family="DejaVu Sans" font-size="15"
fill="magenta"
textLength="250"
direction="rtl"
lengthAdjust="spacingAndGlyphs">اللغة العربية المعيارية الحديثة</text>
<text id="test6rtl" x="255" y="185"
font-family="DejaVu Sans" font-size="15"
fill="orange"
direction="rtl"
textLength="250">اللغة <tspan textLength="100">العربية</tspan> المعيارية الحديثة</text>
<text id="test7rtl" x="255" y="200"
font-family="DejaVu Sans" font-size="15"
fill="purple"
direction="rtl"
lengthAdjust="spacingAndGlyphs"
textLength="250">اللغة <tspan textLength="100" lengthAdjust="spacingAndGlyphs">العربية</tspan> المعيارية الحديثة</text>
<text id="test1ttb" x="265" y="5"
font-family="Krita_Test_Unicode_Variation_A, sans" font-size="15"
writing-mode="vertical-rl"
fill="blue"
textLength="200">ああああ芦芦芦ああああ</text>
<text id="test2ttb" x="280" y="5"
font-family="sans" font-size="15"
writing-mode="vertical-rl"
fill="cyan"
textLength="180">ああああ芦芦芦ああああ<tspan x="295" y="5">ああああ芦芦芦ああああ</tspan></text>
<text id="test3ttb" x="280" y="110"
font-family="sans" font-size="15"
fill="green"
writing-mode="vertical-rl"
textLength="95">ああああ芦芦芦ああああ</text>
<text id="test4ttb" x="295" y="110"
font-family="sans" font-size="15"
fill="lightgreen"
writing-mode="vertical-rl"
textLength="95"
lengthAdjust="spacingAndGlyphs">ああああ芦芦芦ああああ</text>
<text id="test5ttb" x="310" y="5"
font-family="sans" font-size="15"
fill="magenta"
textLength="200"
writing-mode="vertical-rl"
lengthAdjust="spacingAndGlyphs">ああああ芦芦芦ああああ</text>
<text id="test6ttb" x="325" y="5"
font-family="sans" font-size="15"
fill="orange"
writing-mode="vertical-rl"
textLength="200">ああああ<tspan textLength="100">芦芦芦</tspan>ああああ</text>
<text id="test7ttb" x="340" y="5"
font-family="sans" font-size="15"
fill="purple"
lengthAdjust="spacingAndGlyphs"
writing-mode="vertical-rl"
textLength="200">ああああ<tspan textLength="100" lengthAdjust="spacingAndGlyphs">芦芦芦</tspan>ああああ</text>
</g>
</svg>
```
Please view or discuss this issue at https://github.com/w3c/svgwg/issues/899 using your GitHub account
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Received on Sunday, 30 October 2022 13:32:19 UTC