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Apply the drawShadow bounds workaround to the Web HTML backend (flutter/engine#42304)

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Previously the Flutter framework had been inflating the rectangle computed for the bounds of a drawShadow operation in order to work around potential inaccuracies in the SkPicture's bounds calculation.

That workaround is now obsolete for most platforms and was removed from the framework (see https://github.com/flutter/flutter/pull/127052). But the Web HTML backend is using different code for computing shadow bounds.  This PR restores the workaround for Web HTML for consistency with the old behavior.
This commit is contained in:
Jason Simmons 2023-05-26 07:31:26 -07:00 committed by GitHub
parent 916a526271
commit 6bd25a9256
2 changed files with 9 additions and 2 deletions
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9
engine/src/flutter/lib/web_ui/lib/src/engine/shadow.dart
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@ -73,12 +73,19 @@ ui.Rect computePenumbraBounds(ui.Rect shape, double elevation) {
final double dx = elevation * tx;
final double dy = elevation * ty;
final ui.Offset offset = computeShadowOffset(elevation);
return ui.Rect.fromLTRB(
final ui.Rect bounds = ui.Rect.fromLTRB(
shape.left - dx,
shape.top - dy,
shape.right + dx,
shape.bottom + dy,
).shift(offset);
// Expand the bounds rectangle to compensate for inaccuracy in the shadow
// calculation. This is similar to a workaround that had previously been
// used in the Flutter framework to adjust the bounds for shadows drawn
// by Skia.
// (See https://github.com/flutter/flutter/pull/127052)
return bounds.inflate(20);
}
/// Information needed to render a shadow using CSS or canvas.

2
engine/src/flutter/lib/web_ui/test/html/recording_canvas_golden_test.dart
View File

@ -416,7 +416,7 @@ Future<void> testMain() async {
expect(
rc.pictureBounds,
within(
distance: 0.05, from: const Rect.fromLTRB(17.9, 28.5, 103.5, 114.1)),
distance: 0.05, from: const Rect.fromLTRB(0.0, 8.5, 123.5, 134.1)),
);
await checkScreenshot(rc, 'path_with_shadow');
});