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[Impeller][WIp] performance improvements for polyline generation. #52078

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[Impeller][WIp] performance improvements for polyline generation. #52078

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jonahwilliams
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Replace this paragraph with a description of what this PR is changing or adding, and why. Consider including before/after screenshots.

List which issues are fixed by this PR. You must list at least one issue.

If you had to change anything in the flutter/tests repo, include a link to the migration guide as per the breaking change policy.

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@jonahwilliams jonahwilliams mentioned this pull request Apr 13, 2024
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auto-submit bot pushed a commit that referenced this pull request Apr 15, 2024
@jonahwilliams
[Impeller] Use Wang's formula for quad/cubic subdivision. (#52079)
96365c5 
Use a faster method to compute the number of subdivisions of quadradic and cubic curves. Unlike the adaptive subdivison we use this may give us more line segments around straight-ish parts of a curve ... but who cares! the rasterizer can handle it. This is enough to lop off about 2ms from the animated tessellation benchmark (5.5 to 3.5 on a Pixel 7), and there are some additional savings we can book by removing some of the incidental allocations. This part will be done in a follow up (#52078).

### Before

![image](https://github.com/flutter/engine/assets/8975114/8dc45012-3999-4598-ac3b-713e09d5a31f)

### After

![image](https://github.com/flutter/engine/assets/8975114/8a90636f-9698-46e6-bd3f-2f47c8abdbba)

From looking at the proproptions I think this is in the 3x-5x faster range.

Code originally taken from https://github.com/google/skia/blob/main/src/gpu/tessellate/WangsFormula.h
@jonahwilliams
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Following up here: #52131

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