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[Impeller] adjust coverage origin when rounding out SaveLayer bounds. (#161838)

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Fixes https://github.com/flutter/flutter/issues/161374

When we round out the texture size for a saveLayer, also round out the
coverage so that the drawing origin is correct. Otherwise we may
actually cut off the top left edge of rendering.

---------

Co-authored-by: gaaclarke <30870216+gaaclarke@users.noreply.github.com>
This commit is contained in:
Jonah Williams 2025-01-22 16:44:54 -08:00 committed by GitHub
parent 64c808b7c8
commit 948e31d19f
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GPG Key ID: B5690EEEBB952194
3 changed files with 40 additions and 1 deletions
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10
engine/src/flutter/impeller/display_list/canvas.cc
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@ -1017,12 +1017,19 @@ void Canvas::SaveLayer(const Paint& paint,
// sampling mode.
ISize subpass_size;
bool did_round_out = false;
Point coverage_origin_adjustment = Point{0, 0};
if (paint.image_filter) {
subpass_size = ISize(subpass_coverage.GetSize());
} else {
did_round_out = true;
subpass_size =
static_cast<ISize>(IRect::RoundOut(subpass_coverage).GetSize());
// If rounding out, adjust the coverage to account for the subpixel shift.
coverage_origin_adjustment =
Point(subpass_coverage.GetLeftTop().x -
std::floor(subpass_coverage.GetLeftTop().x),
subpass_coverage.GetLeftTop().y -
std::floor(subpass_coverage.GetLeftTop().y));
}
if (subpass_size.IsEmpty()) {
return SkipUntilMatchingRestore(total_content_depth);
@ -1156,7 +1163,8 @@ void Canvas::SaveLayer(const Paint& paint,
subpass_size, //
Color::BlackTransparent() //
)));
save_layer_state_.push_back(SaveLayerState{paint_copy, subpass_coverage});
save_layer_state_.push_back(SaveLayerState{
paint_copy, subpass_coverage.Shift(-coverage_origin_adjustment)});
CanvasStackEntry entry;
entry.transform = transform_stack_.back().transform;

28
engine/src/flutter/impeller/display_list/dl_golden_unittests.cc
View File

@ -4,6 +4,9 @@
#include "impeller/display_list/dl_golden_unittests.h"
#include "display_list/dl_color.h"
#include "display_list/dl_paint.h"
#include "display_list/geometry/dl_geometry_types.h"
#include "flutter/display_list/dl_builder.h"
#include "flutter/impeller/geometry/path_builder.h"
#include "flutter/testing/testing.h"
@ -307,5 +310,30 @@ TEST_P(DlGoldenTest, DashedLinesTest) {
ASSERT_TRUE(OpenPlaygroundHere(builder.Build()));
}
TEST_P(DlGoldenTest, SaveLayerAtFractionalValue) {
// Draws a stroked rounded rect at a fractional pixel value. The coverage must
// be adjusted so that we still have room to draw it, even though it lies on
// the fractional bounds of the saveLayer.
DisplayListBuilder builder;
builder.DrawPaint(DlPaint().setColor(DlColor::kWhite()));
auto save_paint = DlPaint().setAlpha(100);
builder.SaveLayer(nullptr, &save_paint);
builder.DrawRoundRect(DlRoundRect::MakeRectRadius(
DlRect::MakeLTRB(10.5, 10.5, 200.5, 200.5), 10),
DlPaint()
.setDrawStyle(DlDrawStyle::kStroke)
.setStrokeWidth(1.5)
.setColor(DlColor::kBlack()));
builder.DrawCircle(DlPoint::MakeXY(100, 100), 50.5,
DlPaint().setColor(DlColor::kAqua()));
builder.DrawCircle(DlPoint::MakeXY(110, 110), 50.5,
DlPaint().setColor(DlColor::kCyan()));
builder.Restore();
ASSERT_TRUE(OpenPlaygroundHere(builder.Build()));
}
} // namespace testing
} // namespace flutter

3
engine/src/flutter/testing/impeller_golden_tests_output.txt
View File

@ -981,6 +981,9 @@ impeller_Play_DlGoldenTest_GaussianVsRRectBlurScaled_Vulkan.png
impeller_Play_DlGoldenTest_GaussianVsRRectBlur_Metal.png
impeller_Play_DlGoldenTest_GaussianVsRRectBlur_OpenGLES.png
impeller_Play_DlGoldenTest_GaussianVsRRectBlur_Vulkan.png
impeller_Play_DlGoldenTest_SaveLayerAtFractionalValue_Metal.png
impeller_Play_DlGoldenTest_SaveLayerAtFractionalValue_OpenGLES.png
impeller_Play_DlGoldenTest_SaveLayerAtFractionalValue_Vulkan.png
impeller_Play_DlGoldenTest_StrokedRRectFastBlur_Metal.png
impeller_Play_DlGoldenTest_StrokedRRectFastBlur_OpenGLES.png
impeller_Play_DlGoldenTest_StrokedRRectFastBlur_Vulkan.png