[svgwg] Compatibility mid-line rendering attribute to textPath

msand has just created a new issue for https://github.com/w3c/svgwg:

== Compatibility mid-line rendering attribute to textPath ==
Specification: SVG 2, Text chapter, 11.8.3. Text on a path layout rules
https://svgwg.org/svg2-draft/text.html#GlyphMidline
And following list item.

Excerpt:
> Determine the glyph-midline, which is the vertical line in the glyph's coordinate system that goes through the glyph's x-axis midpoint. (In the picture above, the glyph-midline is shown as a dashed line.)
> 
> Position the glyph such that the glyph-midline passes through the midpoint-on-the-path and is perpendicular to the line through the startpoint-on-the-path and the endpoint-on-the-path.

This wording is different from how Chrome, Firefox, Opera etc render text on a path. Only Edge seems to actually implement this. I'm implementing and improving the svg spec conformance of react-native-svg, and have implemented both algorithms almost completely (extending the path for the start to end-point calculation, when midpoint is on the path but either start or end is not, is still missing). https://github.com/react-native-community/react-native-svg/pull/406

I've would like to suggest adding a compatibility 'mid-line' attribute for the 'textPath' element, with the values 'sharp | smooth', initial value 'smooth'. 
The initial value would be the strict interpretation of the spec, and sharp would be the one currently implemented in the wild.

```
 Name
 mid-line
 Value
 sharp | smooth
 initial value
 smooth
 Animatable
 yes
```

The current common behavior is that it doesn't e.g., bend text smoothly along a right angle curve, (like Edge does) but keeps the mid-line orthogonal to the mid-point tangent at all times instead.

I've already added this attribute to react-native-svg in my fork:
https://github.com/msand/react-native-svg/commit/d08103168a4ee78c163f2614e5f3e8e7cede6b9d

Example screenshot: (Smooth on top, sharp below)
![screenshot_1501031659](https://user-images.githubusercontent.com/1131362/28600171-fddeb4f6-71b8-11e7-8eee-f7d275f839ee.png)


Please view or discuss this issue at https://github.com/w3c/svgwg/issues/337 using your GitHub account

Received on Wednesday, 26 July 2017 01:18:14 UTC