[Impeller] Fix overdraw in DrawRect geometry #174735
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This pull request addresses an overdraw issue in DrawRect geometry for stroked rectangles. For Bevel and Miter joins, the vertex generation has been updated to create geometry without inherent overdraw, and a special case has been added for thick strokes that collapse on themselves. For Round joins, the geometry is now flagged to use the pipeline's overdraw prevention, which fixes the visual artifact at a performance cost as noted. New tests are included to verify the rendering of wide stroked rectangles.
engine/src/flutter/impeller/display_list/aiks_dl_basic_unittests.cc
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Golden file changes have been found for this pull request. Click here to view and triage (e.g. because this is an intentional change). If you are still iterating on this change and are not ready to resolve the images on the Flutter Gold dashboard, consider marking this PR as a draft pull request above. You will still be able to view image results on the dashboard, commenting will be silenced, and the check will not try to resolve itself until marked ready for review. For more guidance, visit Writing a golden file test for Reviewers: Read the Tree Hygiene page and make sure this patch meets those guidelines before LGTMing. |
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Golden file changes are available for triage from new commit, Click here to view. For more guidance, visit Writing a golden file test for Reviewers: Read the Tree Hygiene page and make sure this patch meets those guidelines before LGTMing. |
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All tests passed and the goldens for the new tests look correct (no overdraw anomalies that I could see). This PR is ready for review now. |
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ping @gaaclarke @chinmaygarde |
engine/src/flutter/impeller/display_list/aiks_dl_basic_unittests.cc
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| // Most(all?) of our geometry is produced in full with an explicit mode | ||
| // specified in the returned GeometryResult, but just in case we missed | ||
| // a case, the safest mode to return here is kPreventOverdraw. | ||
| return GeometryResult::Mode::kPreventOverdraw; |
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I may be missing something obvious. But this should no longer be necessary now right?
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My reading of "PreventOverdraw" is "there may be overlapping triangles produced by this geometry but I want you to render them as though there aren't". The fix for the linked issue is either to just specify this result mode, or not produce any overlapping trianges. Not both I'd think.
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In case anyone adds a new case somewhere that isn't explicitly tagged, I wanted to make sure that we returned the safest option.
This "you can specify it if you want, the default is the one that is least safe but fastest, or you can return it from a method and some of our code might fill it in for you" spectrum of how this Mode is handled can be confusing and I don't think we are doing anyone any maintenance favors by having all of the defaults be "do it the fastest you can and don't worry about the consequences"...?
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Put another way, I bet the test passes if you only specify this and literally nothing else. So, why not just specify this for simplicity. As I understand, this specification forces a slower path to account for overlaps.
Or am I just mistaken?
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It also runs 50% slower.
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kPreventOverdraw isn't magic. It costs - a lot.
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Yeah, so why specify that as the default on the off chance we missed some edge case.
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Oh poop, I missed the spot where you explicitly set the mode to be normal for the known fast cases.
I take it that its by far the most common case? If so, all good 😊
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It's not just the most common case, it never falls through. I removed it for now, but I don't like the entire design of this API that assumes things that have consequences that aren't immediately obvious and we construct an entire operation.
| vertex_count * sizeof(Point), alignof(Point), | ||
| [hsw = half_stroke_width, &rect, vertex_count, | ||
| &trigs](uint8_t* buffer) { | ||
| [hsw = half_stroke_width, &rect, vertex_count, &trigs, |
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No abbreviations ("hsw")
https://google.github.io/styleguide/cppguide.html#General_Naming_Rules
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Not going to change this. The following code would become unreadable and unmaintainable.
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However, a name should not distract the reader by repeating information that's present in the immediate context. Generally, this means that descriptiveness should be proportional to the name's scope of visibility.
hsw has a short scope of visibility and is defined in the calls of each of these lambdas. It also keeps the coordinate equations well-aligned and balanced.
| Scalar right = rect.GetRight(); | ||
| Scalar bottom = rect.GetBottom(); | ||
| auto vertices = reinterpret_cast<Point*>(buffer); | ||
| // Zig-zag pattern: UL, UR, LL, LR |
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Upper-left, upper-right, lower-left, lower-right?
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Please, update the comment to avoid these abbreviations.
chinmaygarde
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Sorry about the confusion regarding overlap content mode in the default case.
I can totally empathize with the argument that we should fall back to a known safe but slow technique in case we missed something. OTOH, if we missed something, I'd rather folks report it to us as a bug instead of a mysterious performance issue that we'd have a harder time tracking down. Right now, I don't think there are cases we know we will miss. So I don't want to introduce a potential performance cliff.
Perhaps @gaaclarke has a different take but the current state of the patch without the fallback lgtm.
I'm not as familiar as you guys are with the ramifications of using different |
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The gist of it is that strokes that overlap but also have a translucent stroke color will look weird where they overlap. I'll need to lookup the technique used to render them right but the a solid stroke is rendered offscreen and composited with the alpha component onscreen. Hence the slowness. |
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Golden file changes are available for triage from new commit, Click here to view. For more guidance, visit Writing a golden file test for Reviewers: Read the Tree Hygiene page and make sure this patch meets those guidelines before LGTMing. |
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Looks like the golden diffs are for the test cases you added 🎉 |
Roll Flutter from 6b18740 to 87d5b75 (88 revisions) flutter/flutter@6b18740...87d5b75 2025-09-05 bkonyi@google.com [ Device Lab ] Add regression testing for flutter/flutter#174952 (flutter/flutter#174956) 2025-09-05 engine-flutter-autoroll@skia.org Roll Skia from 0ca53adfc6cc to 845ec125e94c (2 revisions) (flutter/flutter#174978) 2025-09-05 bruno.leroux@gmail.com [a11y-app] Fix NavigationRail leading and trailing labels (flutter/flutter#174861) 2025-09-05 engine-flutter-autoroll@skia.org Roll Skia from d7e99be07d5d to 0ca53adfc6cc (5 revisions) (flutter/flutter#174972) 2025-09-05 engine-flutter-autoroll@skia.org Roll Fuchsia Linux SDK from izfNA3o_2zL4Cjqmy... to xG_uERsxHvUwFHpF2... (flutter/flutter#174970) 2025-09-04 bruno.leroux@gmail.com Fix IconButton.color overrided by IconButtomTheme (flutter/flutter#174515) 2025-09-04 mdebbar@google.com [web] Reuse chrome instance to run all flutter tests (flutter/flutter#174957) 2025-09-04 pedromassango.developer@gmail.com fix(Semantics): Ensure semantics properties take priority over button's (flutter/flutter#174473) 2025-09-04 15619084+vashworth@users.noreply.github.com Make every LLDB Init error message actionable (flutter/flutter#174726) 2025-09-04 jhy03261997@gmail.com Fix table cell semantics rect alignment issues. (flutter/flutter#174914) 2025-09-04 34465683+rkishan516@users.noreply.github.com Fix: Use route navigator for CupertinoSheetRoute pop (flutter/flutter#173103) 2025-09-04 bkonyi@google.com [ Widget Preview] Add `group` property to `Preview` (flutter/flutter#174849) 2025-09-04 47866232+chunhtai@users.noreply.github.com Allow OverlayPortal.overlayChildLayoutBuilder to choose root Overlay (flutter/flutter#174239) 2025-09-04 engine-flutter-autoroll@skia.org Roll Skia from 7c2f502e3304 to d7e99be07d5d (18 revisions) (flutter/flutter#174936) 2025-09-04 mdebbar@google.com Remove 'terms of use' wording from web_unicode (flutter/flutter#174939) 2025-09-04 bkonyi@google.com [ Tool ] Remove leftover Android x86 deprecation warning constant (flutter/flutter#174941) 2025-09-04 15619084+vashworth@users.noreply.github.com Prevent potential crash when accessing window in FlutterSceneDelegate (flutter/flutter#174873) 2025-09-04 engine-flutter-autoroll@skia.org Roll Packages from 42bb347 to 98580c6 (5 revisions) (flutter/flutter#174943) 2025-09-04 bkonyi@google.com [ Device Lab ] Fix wakefulness check to only match log entries with string values (flutter/flutter#174953) 2025-09-04 bruno.leroux@gmail.com Fix expanded DropdownMenu panel is shorter than text field (flutter/flutter#174443) 2025-09-04 31859944+LongCatIsLooong@users.noreply.github.com Add a `viewController` property to the ios/macOS `FlutterPluginRegistrar` protocol (flutter/flutter#174168) 2025-09-03 engine-flutter-autoroll@skia.org Roll Fuchsia Linux SDK from J3T_wZqL_57mRfWky... to izfNA3o_2zL4Cjqmy... (flutter/flutter#174908) 2025-09-03 47866232+chunhtai@users.noreply.github.com Wires up Android API to set section locale (flutter/flutter#173364) 2025-09-03 chinmaygarde@google.com Delete impeller::SPrintF. (flutter/flutter#174900) 2025-09-03 ahmedsameha1@gmail.com Make sure that a DropdownMenuFormField doesn't crash in 0x0 environment (flutter/flutter#174777) 2025-09-03 mdebbar@google.com Remove unnecessary `presubmit_max_attempts` from .ci.yaml (flutter/flutter#174885) 2025-09-03 mdebbar@google.com Use local canvaskit in `dart_data_asset_test.dart` (flutter/flutter#174891) 2025-09-03 98614782+auto-submit[bot]@users.noreply.github.com Reverts "Mark Linux web_canvaskit_tests_7_last as bringup (#174878)" (flutter/flutter#174897) 2025-09-03 victorsanniay@gmail.com Correct intrinsics calculation for CupertinoTextField with placeholder (flutter/flutter#174889) 2025-09-03 11901536+romaingyh@users.noreply.github.com Considers large title height in CupertinoNavigationBar's preferred size (flutter/flutter#173722) 2025-09-03 victorsanniay@gmail.com [A11y] Add semantics for CupertinoExpansionTile (flutter/flutter#174480) 2025-09-03 sokolovskyi.konstantin@gmail.com Fix LinearProgressIndicator track painting. (flutter/flutter#173108) 2025-09-03 matt.boetger@gmail.com update triage documentation to include team-android (flutter/flutter#174850) 2025-09-03 mdebbar@google.com Update `test_timeout_secs` to match `timeout` for `Linux web_skwasm_tests_*` and `Linux web_canvaskit_tests_*` (flutter/flutter#174881) 2025-09-03 engine-flutter-autoroll@skia.org Roll Packages from 5d785a0 to 42bb347 (10 revisions) (flutter/flutter#174876) 2025-09-03 chinmaygarde@google.com Fixup formatting of gn files in the old buildroot. (flutter/flutter#174852) 2025-09-03 iinozemtsev@google.com Roll Dart SDK to 3.10.0-162.1.beta (flutter/flutter#174834) 2025-09-03 mdebbar@google.com Mark Linux web_canvaskit_tests_7_last as bringup (flutter/flutter#174878) 2025-09-02 flar@google.com [Impeller] Fix overdraw in DrawRect geometry (flutter/flutter#174735) 2025-09-02 chinmaygarde@google.com Patch .clang-format files to specify C++20. (flutter/flutter#174848) 2025-09-02 mosum@google.com Add data assets (flutter/flutter#174685) 2025-09-02 mohellebiabdessalem@gmail.com refactors `FlutterPlugin.kt` to use one line statement in the `into` bloc (flutter/flutter#174759) 2025-09-02 47866232+chunhtai@users.noreply.github.com Ensures initial semantics state is sent to engine (flutter/flutter#174845) 2025-09-02 43054281+camsim99@users.noreply.github.com [Android] Break up plugin_test integration tests (flutter/flutter#174728) 2025-09-02 34465683+rkishan516@users.noreply.github.com Fix: Assertion failure in RawScrollbarState with dynamic controller assignment (flutter/flutter#173156) 2025-09-02 engine-flutter-autoroll@skia.org Roll Skia from 359f3d7cc7ed to 7c2f502e3304 (1 revision) (flutter/flutter#174844) ...
Fixes flutter#174579 Vertex lists for stroked rects were fixed by being more careful about the creation of the vertices so that they have no inherent overdraw. These operations continue to use the fastest kNormal vertex mode but no longer create rendering artifacts due to multiple triangles covering the same area.
Fixes flutter#174579 Vertex lists for stroked rects were fixed by being more careful about the creation of the vertices so that they have no inherent overdraw. These operations continue to use the fastest kNormal vertex mode but no longer create rendering artifacts due to multiple triangles covering the same area.
Roll Flutter from 6b18740 to 87d5b75 (88 revisions) flutter/flutter@6b18740...87d5b75 2025-09-05 bkonyi@google.com [ Device Lab ] Add regression testing for flutter/flutter#174952 (flutter/flutter#174956) 2025-09-05 engine-flutter-autoroll@skia.org Roll Skia from 0ca53adfc6cc to 845ec125e94c (2 revisions) (flutter/flutter#174978) 2025-09-05 bruno.leroux@gmail.com [a11y-app] Fix NavigationRail leading and trailing labels (flutter/flutter#174861) 2025-09-05 engine-flutter-autoroll@skia.org Roll Skia from d7e99be07d5d to 0ca53adfc6cc (5 revisions) (flutter/flutter#174972) 2025-09-05 engine-flutter-autoroll@skia.org Roll Fuchsia Linux SDK from izfNA3o_2zL4Cjqmy... to xG_uERsxHvUwFHpF2... (flutter/flutter#174970) 2025-09-04 bruno.leroux@gmail.com Fix IconButton.color overrided by IconButtomTheme (flutter/flutter#174515) 2025-09-04 mdebbar@google.com [web] Reuse chrome instance to run all flutter tests (flutter/flutter#174957) 2025-09-04 pedromassango.developer@gmail.com fix(Semantics): Ensure semantics properties take priority over button's (flutter/flutter#174473) 2025-09-04 15619084+vashworth@users.noreply.github.com Make every LLDB Init error message actionable (flutter/flutter#174726) 2025-09-04 jhy03261997@gmail.com Fix table cell semantics rect alignment issues. (flutter/flutter#174914) 2025-09-04 34465683+rkishan516@users.noreply.github.com Fix: Use route navigator for CupertinoSheetRoute pop (flutter/flutter#173103) 2025-09-04 bkonyi@google.com [ Widget Preview] Add `group` property to `Preview` (flutter/flutter#174849) 2025-09-04 47866232+chunhtai@users.noreply.github.com Allow OverlayPortal.overlayChildLayoutBuilder to choose root Overlay (flutter/flutter#174239) 2025-09-04 engine-flutter-autoroll@skia.org Roll Skia from 7c2f502e3304 to d7e99be07d5d (18 revisions) (flutter/flutter#174936) 2025-09-04 mdebbar@google.com Remove 'terms of use' wording from web_unicode (flutter/flutter#174939) 2025-09-04 bkonyi@google.com [ Tool ] Remove leftover Android x86 deprecation warning constant (flutter/flutter#174941) 2025-09-04 15619084+vashworth@users.noreply.github.com Prevent potential crash when accessing window in FlutterSceneDelegate (flutter/flutter#174873) 2025-09-04 engine-flutter-autoroll@skia.org Roll Packages from 42bb347 to 98580c6 (5 revisions) (flutter/flutter#174943) 2025-09-04 bkonyi@google.com [ Device Lab ] Fix wakefulness check to only match log entries with string values (flutter/flutter#174953) 2025-09-04 bruno.leroux@gmail.com Fix expanded DropdownMenu panel is shorter than text field (flutter/flutter#174443) 2025-09-04 31859944+LongCatIsLooong@users.noreply.github.com Add a `viewController` property to the ios/macOS `FlutterPluginRegistrar` protocol (flutter/flutter#174168) 2025-09-03 engine-flutter-autoroll@skia.org Roll Fuchsia Linux SDK from J3T_wZqL_57mRfWky... to izfNA3o_2zL4Cjqmy... (flutter/flutter#174908) 2025-09-03 47866232+chunhtai@users.noreply.github.com Wires up Android API to set section locale (flutter/flutter#173364) 2025-09-03 chinmaygarde@google.com Delete impeller::SPrintF. (flutter/flutter#174900) 2025-09-03 ahmedsameha1@gmail.com Make sure that a DropdownMenuFormField doesn't crash in 0x0 environment (flutter/flutter#174777) 2025-09-03 mdebbar@google.com Remove unnecessary `presubmit_max_attempts` from .ci.yaml (flutter/flutter#174885) 2025-09-03 mdebbar@google.com Use local canvaskit in `dart_data_asset_test.dart` (flutter/flutter#174891) 2025-09-03 98614782+auto-submit[bot]@users.noreply.github.com Reverts "Mark Linux web_canvaskit_tests_7_last as bringup (#174878)" (flutter/flutter#174897) 2025-09-03 victorsanniay@gmail.com Correct intrinsics calculation for CupertinoTextField with placeholder (flutter/flutter#174889) 2025-09-03 11901536+romaingyh@users.noreply.github.com Considers large title height in CupertinoNavigationBar's preferred size (flutter/flutter#173722) 2025-09-03 victorsanniay@gmail.com [A11y] Add semantics for CupertinoExpansionTile (flutter/flutter#174480) 2025-09-03 sokolovskyi.konstantin@gmail.com Fix LinearProgressIndicator track painting. (flutter/flutter#173108) 2025-09-03 matt.boetger@gmail.com update triage documentation to include team-android (flutter/flutter#174850) 2025-09-03 mdebbar@google.com Update `test_timeout_secs` to match `timeout` for `Linux web_skwasm_tests_*` and `Linux web_canvaskit_tests_*` (flutter/flutter#174881) 2025-09-03 engine-flutter-autoroll@skia.org Roll Packages from 5d785a0 to 42bb347 (10 revisions) (flutter/flutter#174876) 2025-09-03 chinmaygarde@google.com Fixup formatting of gn files in the old buildroot. (flutter/flutter#174852) 2025-09-03 iinozemtsev@google.com Roll Dart SDK to 3.10.0-162.1.beta (flutter/flutter#174834) 2025-09-03 mdebbar@google.com Mark Linux web_canvaskit_tests_7_last as bringup (flutter/flutter#174878) 2025-09-02 flar@google.com [Impeller] Fix overdraw in DrawRect geometry (flutter/flutter#174735) 2025-09-02 chinmaygarde@google.com Patch .clang-format files to specify C++20. (flutter/flutter#174848) 2025-09-02 mosum@google.com Add data assets (flutter/flutter#174685) 2025-09-02 mohellebiabdessalem@gmail.com refactors `FlutterPlugin.kt` to use one line statement in the `into` bloc (flutter/flutter#174759) 2025-09-02 47866232+chunhtai@users.noreply.github.com Ensures initial semantics state is sent to engine (flutter/flutter#174845) 2025-09-02 43054281+camsim99@users.noreply.github.com [Android] Break up plugin_test integration tests (flutter/flutter#174728) 2025-09-02 34465683+rkishan516@users.noreply.github.com Fix: Assertion failure in RawScrollbarState with dynamic controller assignment (flutter/flutter#173156) 2025-09-02 engine-flutter-autoroll@skia.org Roll Skia from 359f3d7cc7ed to 7c2f502e3304 (1 revision) (flutter/flutter#174844) ...
Fixes flutter#174579 Vertex lists for stroked rects were fixed by being more careful about the creation of the vertices so that they have no inherent overdraw. These operations continue to use the fastest kNormal vertex mode but no longer create rendering artifacts due to multiple triangles covering the same area.
Fixes #174579
Vertex lists for stroked rects were fixed by being more careful about the creation of the vertices so that they have no inherent overdraw. These operations continue to use the fastest kNormal vertex mode but no longer create rendering artifacts due to multiple triangles covering the same area.