How to get stable layout when zooming text with CanvasKit?

[Yifeng Wang]

Hi, I'm using CanvasKit to render multi-line text. When user performs zooming, the text width and font size are scaled together. But in this case, the layout result is unstable, jumps in line height or line break can be observed. See online fiddle:

https://jsfiddle.skia.org/canvaskit/1722df96d460688cd8e6d8358017aad0a3e27cede8bf2d49e0c6e670c33804a7

Is this behavior expected (I filed an issue at https://bugs.chromium.org/p/skia/issues/detail?id=12042 but not sure if it's a bug)? Text scaling in browser doesn't have this issue, can we achieve similar result with some workaround? Thanks.

Regards

Yifeng Wang

[Shachar Langbeheim]

You can convert the text to a SkPath at a constant font size, and then scale the path. 
See this discussion:
https://groups.google.com/g/skia-discuss/c/0P6S8gkx3n8/m/Px_6T15tBgAJ?pli=1

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[Mike Reed]

Very nice test case!

Skia has settings (on the SkFont) that can smooth this out, but we may not have exposed them all to CanvasKit yet.

Have you tried font.setSubpixel(true) or font.setLinearMetrics(true) ?

We also have a baseline_snap setting which is not exposed. It may be needed to fixed the vertical snapping...

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[Ben Wagner]

Also "font.setHinting(CanvasKit.FontHinting.None);". Though "Slight"
should also work (it tends to hint in only the vertical direction). If
hinting is Normal or Full then hinting will happen, which expressly
trades off outline scalability for legibility.

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