[SVG] Fix precision loss in non-scaling-stroke with large coordinate translations #55856
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translations When SVG paths use vector-effect="non-scaling-stroke" with large viewBox coordinate translations (e.g. viewBox="2137678 0 96 50"), vertical lines would disappear due to floating-point precision loss in the transform calculations. The issue occurred because `ComputeNonScalingStrokeTransform()` was zeroing out translation components (SetE(0), SetF(0)) under the assumption that "stroke width is independent of translation." While this is true for stroke width calculation, removing translation can lead to large coordinate values, increasing the risk of precision loss as seen in the bug. In this CL, we preserve translation components in the non-scaling-stroke transform. This mitigates the precision loss caused by large offset but we only preserve this translation for non-scaling-stroke-path and not in general. Bug: 40718465 Change-Id: Id92acf5c5798eab264df33d8a4af4759376483f6 Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/7106499 Reviewed-by: Fredrik Söderquist <[email protected]> Reviewed-by: Vinay Singh <[email protected]> Commit-Queue: Divyansh Mangal <[email protected]> Cr-Commit-Position: refs/heads/main@{#1540470}
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When SVG paths use vector-effect="non-scaling-stroke" with large
viewBox coordinate translations (e.g. viewBox="2137678 0 96 50"),
vertical lines would disappear due to floating-point precision loss
in the transform calculations.
The issue occurred because
ComputeNonScalingStrokeTransform()waszeroing out translation components (SetE(0), SetF(0)) under the
assumption that "stroke width is independent of translation."
While this is true for stroke width calculation, removing
translation can lead to large coordinate values, increasing the
risk of precision loss as seen in the bug.
In this CL, we preserve translation components in the
non-scaling-stroke transform. This mitigates the precision loss
caused by large offset but we only preserve this translation for
non-scaling-stroke-path and not in general.
Bug: 40718465
Change-Id: Id92acf5c5798eab264df33d8a4af4759376483f6
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/7106499
Reviewed-by: Fredrik Söderquist <[email protected]>
Reviewed-by: Vinay Singh <[email protected]>
Commit-Queue: Divyansh Mangal <[email protected]>
Cr-Commit-Position: refs/heads/main@{#1540470}