Skip to content

Fix unintentionally joined path contours #187522

New issue

Have a question about this project? Sign up for a free GitHub account to open an issue and contact its maintainers and the community.

Sign up for GitHub

By clicking “Sign up for GitHub”, you agree to our terms of service and privacy statement. We’ll occasionally send you account related emails.

Already on GitHub? Sign in to your account

Merged
auto-submit merged 2 commits into from
Jun 4, 2026
+76 −3
Merged

Fix unintentionally joined path contours #187522

Show file tree
Hide file tree
Changes from all commits
Commits
Show all changes
2 commits
Select commit Hold shift + click to select a range
5fa6e59
Fix unintentionally joined path contours
b-luk Jun 3, 2026
3ec6e33
add golden test
b-luk Jun 3, 2026
File filter

Filter by extension

Filter by extension
Conversations
Failed to load comments.
Loading
Jump to
Jump to file
Failed to load files.
Loading
Diff view
Diff view
26 changes: 26 additions & 0 deletions engine/src/flutter/impeller/display_list/aiks_dl_path_unittests.cc
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -983,6 +983,32 @@ TEST_P(AiksTest, TwoContourPathWithSinglePointContour) {
ASSERT_TRUE(OpenPlaygroundHere(builder.Build()));
}

TEST_P(AiksTest, TwoContourPathWithConnectingLines) {
DisplayListBuilder builder;

DlPaint paint;
paint.setColor(DlColor::kRed());
paint.setDrawStyle(DlDrawStyle::kStroke);
paint.setStrokeWidth(15.0);

builder.Translate(100, 0);
for (auto join : std::vector<DlStrokeJoin>{
DlStrokeJoin::kMiter, DlStrokeJoin::kRound, DlStrokeJoin::kBevel}) {
builder.Translate(0, 100);
paint.setStrokeJoin(join);

DlPathBuilder path_builder;
path_builder.MoveTo(DlPoint(0, 0));
path_builder.LineTo(DlPoint(50, 50));
path_builder.MoveTo(DlPoint(50, 50));
path_builder.LineTo(DlPoint(100, 0));

builder.DrawPath(path_builder.TakePath(), paint);
}

ASSERT_TRUE(OpenPlaygroundHere(builder.Build()));
}

TEST_P(AiksTest, StrokeCapsAndJoins) {
DisplayListBuilder builder;
builder.Scale(GetContentScale().x, GetContentScale().y);
Expand Down
51 changes: 49 additions & 2 deletions engine/src/flutter/impeller/entity/geometry/geometry_unittests.cc
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -810,7 +810,7 @@ TEST(EntityGeometryTest, TwoLineSegmentsRightTurnStrokeVerticesBevelJoin) {
Point(30, 25),
Point(30, 15),

// The points for the second segment (120, 20) -> (130, 20)
// The points for the second segment (30, 20) -> (30, 30)
Point(25, 20),
Point(35, 20),
Point(25, 30),
Expand Down Expand Up @@ -844,7 +844,7 @@ TEST(EntityGeometryTest, TwoLineSegmentsLeftTurnStrokeVerticesBevelJoin) {
Point(30, 25),
Point(30, 15),

// The points for the second segment (120, 20) -> (130, 20)
// The points for the second segment (30, 20) -> (30, 10)
Point(35, 20),
Point(25, 20),
Point(35, 10),
Expand All @@ -854,6 +854,53 @@ TEST(EntityGeometryTest, TwoLineSegmentsLeftTurnStrokeVerticesBevelJoin) {
EXPECT_EQ(points, expected);
}

TEST(EntityGeometryTest, TwoLineSegmentsInDifferentContoursAreNotJoined) {
flutter::DlPathBuilder path_builder;
// First contour with a single line.
path_builder.MoveTo({20, 20});
path_builder.LineTo({30, 20});
// Starts a new contour with a MoveTo command. The start of the new contour is
// specified to be the same as the end of the previous contour.
path_builder.MoveTo({30, 20});
// Add a line in the second contour.
path_builder.LineTo({30, 30});
flutter::DlPath path = path_builder.TakePath();

auto points = ImpellerEntityUnitTestAccessor::GenerateSolidStrokeVertices(
path,
{
.width = 10.0f,
.cap = Cap::kButt,
.join = Join::kBevel,
Copy link
Copy Markdown
Contributor

@flar flar Jun 3, 2026

Choose a reason for hiding this comment

The reason will be displayed to describe this comment to others. Learn more.

I would do a golden test of this case with all 3 join types.

Copy link
Copy Markdown
Contributor Author

@b-luk b-luk Jun 3, 2026

Choose a reason for hiding this comment

The reason will be displayed to describe this comment to others. Learn more.

Done. Added a golden test

Before:
Image

After:
Image

.miter_limit = 4.0f,
},
1.0f);

std::vector<Point> expected = {
// The points for the first segment (20, 20) -> (30, 20)
Point(20, 25),
Point(20, 15),
Point(30, 25),
Point(30, 15),

// The glue points that allow us to "pick up the pen" between segments.
// This prevents segments in different contours from being unintentionally
// joined with a bevel.
Point(30, 20),
Point(30, 20),
Point(30, 20),
Point(30, 20),

// The points for the second segment (30, 20) -> (30, 30)
Point(25, 20),
Point(35, 20),
Point(25, 30),
Point(35, 30),
};

EXPECT_EQ(points, expected);
}

TEST(EntityGeometryTest, TwoLineSegmentsRightTurnStrokeVerticesMiterJoin) {
flutter::DlPathBuilder path_builder;
path_builder.MoveTo({20, 20});
Expand Down
2 changes: 1 addition & 1 deletion engine/src/flutter/impeller/entity/geometry/stroke_path_geometry.cc
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -155,7 +155,7 @@ class StrokePathSegmentReceiver : public PathAndArcSegmentReceiver {
protected:
// |SegmentReceiver|
void BeginContour(Point origin, bool will_be_closed) override {
if (has_prior_contour_ && origin != last_point_) {
if (has_prior_contour_) {
Copy link
Copy Markdown
Contributor

@flar flar Jun 3, 2026

Choose a reason for hiding this comment

The reason will be displayed to describe this comment to others. Learn more.

The only question I would have is whether we need all 4 of these vertices if the 2 points are the same, but it shouldn't hurt anything I don't think?

Copy link
Copy Markdown
Contributor Author

@b-luk b-luk Jun 3, 2026

Choose a reason for hiding this comment

The reason will be displayed to describe this comment to others. Learn more.

I think if the 2 points are the same, we only need 2 extra vertices instead of all 4. But like you said, I don't think it hurts to have 4. And I like that this keeps the code more consistent and simpler with no extra branching for the same vs different cases.

// We only append these extra points if we have had a prior contour.
vtx_builder_.AppendVertex(last_point_);
vtx_builder_.AppendVertex(last_point_);
Expand Down
Loading