Use preTranslate when applying offset to matrix #21648

knopp · 2020-10-07T12:39:24Z

Description

matrix.preTranslate(x,y) is identical to matrix.setConcat(matrix, SkMatrix::Translate(x,y)) which is the desired effect.

Related Issues

flutter/flutter#33939

Tests

I added the following tests:

OpacityLayerTest.TranslateChildren

Checklist

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I read the contributor guide and followed the process outlined there for submitting PRs.
I signed the CLA.
I read and followed the C++, Objective-C, Java style guides for the engine.
I read the tree hygiene wiki page, which explains my responsibilities.
I updated/added relevant documentation.
All existing and new tests are passing.
I am willing to follow-up on review comments in a timely manner.

Breaking Change

Did any tests fail when you ran them? Please read handling breaking changes.

No, no existing tests failed, so this is not a breaking change.
Yes, this is a breaking change. If not, delete the remainder of this section.

chinmaygarde · 2020-10-22T22:15:00Z

cc @liyuqian who wrote the original version.

liyuqian · 2020-10-23T04:09:20Z

@knopp : do you happen to also have a sample Flutter app that exhibits the difference before and after this PR? I'm very curious about what triggered you to discover this issue, and I'd like to dive deep to see if there are similar issues in other places (e.g., in PictureLayer). I personally tried the gallery app but couldn't find anything. A sample app would also help us see whether someone could rely on the old behavior which makes this a breaking change.

knopp · 2020-10-23T04:39:45Z

@liyuqian, This is related to partial redraw, which is work in progress. The issue here is that if I compute a damage area between last frame and current and then set it as cull-rect in preroll, some layers will be culled out even though they are within damage area due to wrongly calculated screen-space coordinates (as the unit test shows).

Given that this only causes issue when doing partial repaint you can't really reproduce it with current engine code. But I also can't imagine how any app would rely on wrong screen-space layer coordinates during pre-roll.

There are few other subtle issues that manifest while doing partial repaint related to Backdrop and ImageFilterLayers bounds, but I plan to address them in separate PRs.

flar · 2020-10-23T18:37:38Z

In both cases (opacity and picture layer), these layers use SkMatrix::postTranslate in their preroll, but leaf_nodes_canvas->translate in their Paint methods. The canvas translate method uses SkM44::preTranslate to do the operation.

(Actually, opacity uses a mixture of leaf_nodes_canvas and internal_nodes_canvas in its Paint method whereas picture uses only the leaf version. I don't know if that is another issue to consider...?)

The matrix in the Preroll method is only used for rasterizing layers AFAICT, and since we ignore the translation when we rasterize the layer, it won't affect the resulting image. During paint we then work out where to place the rasterized image and at that point the translation is correct and so we put it in the right position. So, even raster caching wouldn't detect this issue.

But, we do integer CTM adjustments on the transforms which might round in different directions if the offset was a fractional pixel, so this could lead to "off by 1" errors in the placement of cached layers?

knopp · 2020-10-23T18:45:27Z

Good point with the integer CTM. I think both ::Diff and ::Preroll needs be consistent with ::Paint for partial redraws.

liyuqian · 2020-10-26T06:56:52Z

The off by 1 error should be fine as we've already relaxed the constraint in

engine/flow/raster_cache.cc

Line 32 in 412e14d

std::abs(bounds.size().width() - image_->dimensions().width()) <= 1 &&

Since this translation only affects the raster cache slightly, I'm ready to approve it. Let's also correct the usage in PictureLayer to make it consistent. Then I think it's ready to merge.

knopp · 2020-10-26T16:25:33Z

Since this translation only affects the raster cache slightly, I'm ready to approve it. Let's also correct the usage in PictureLayer to make it consistent. Then I think it's ready to merge.

Not entirely sure what you mean. The patch already changes PictureLayer to preTranslate here. Is there something else you have in mind?

liyuqian

Ah, I missed that file. LGTM!

flar

That's a +1 from me too...

matrix.preTranslate(x,y) is identical to matrix.setConcat(matrix, SkMatrix::Translate(x,y));

…ne#21648)

* 53d5d68 Add dart-lang/sdk's new package:clock dependency (flutter/engine#22142) * c32e3d8 Roll Skia from 7737a5bd2510 to 5567a6091ceb (8 revisions) (flutter/engine#22146) * 376045c Roll Fuchsia Linux SDK from XYN02FThN... to UKgKCjxSA... (flutter/engine#22147) * 03395de Roll Fuchsia Mac SDK from GKPwGj1Ux... to xHjtLQPQ5... (flutter/engine#22151) * 0c7e952 Manual Dart SDK roll 6e015bd9cddb to 9c6e76468ca4 (6 revisions (flutter/engine#22153) * e5f168a Update constraint to latest integration test (flutter/engine#22169) * e61e8c2 Smooth window resizing on macOS (flutter/engine#21525) * acece00 Allow parse_and_send to use access tokens (flutter/engine#22019) * 0270632 Includes roles for links, checkboxes, and radio buttons in semantics (flutter/engine#22061) * 632354d Roll Fuchsia Linux SDK from UKgKCjxSA... to PY5hNI-wY... (flutter/engine#22175) * 62d50af Add plumbing for command line arguments on Windows (flutter/engine#22094) * 06b0910 Fix possible use of std::moved value in Rasterizer (flutter/engine#22125) * 005dec4 [web] Clean up unused previousStyle logic (flutter/engine#22150) * ca05bdc Roll Skia from 5567a6091ceb to f548a028ce70 (7 revisions) (flutter/engine#22155) * 5b07ac4 Roll Fuchsia Mac SDK from xHjtLQPQ5... to ICK_JlnKJ... (flutter/engine#22188) * d615a97 Roll Fuchsia Linux SDK from PY5hNI-wY... to Usec4YBzR... (flutter/engine#22197) * 11ed711 Invalidate the cached SkParagraph font collection when a new font manager is installed (flutter/engine#22157) * 07c780b [web] Assign default natural width/height for svgs that report 0,0 on firefox and ie11 (flutter/engine#22184) * b54bb88 Migrate runZoned to runZonedGuarded (flutter/engine#22198) * 247139a [web] Fix transform not invalidating path bounds causing debugValidate failure (flutter/engine#22172) * e4dffc1 [web] Fix scroll wheel line delta on Firefox. (flutter/engine#21928) * d6627c6 Reland [ios] Refactor IOSSurface factory and unify surface creation (flutter/engine#22016) * ce1dd11 Standardize macro names for dartdoc macros (flutter/engine#22180) * f81bc37 [profiling] Handle thread_info to account for killed threads (flutter/engine#22170) * fd94c86 Fix for firefox custom clipping (flutter/engine#22182) * 9ccf9f1 bring back build_test to ensure we validate licenses (flutter/engine#22201) * 38f6665 Set strut font to Roboto if the given font hasn't been registered (flutter/engine#22129) * caf32d5 Add a proc table version of embedder API (flutter/engine#21813) * ed0f477 Use preTranslate when applying offset to matrix (flutter/engine#21648) * b457e2d Refactor make_mock_engine into fl_test (flutter/engine#21585) * 28497c8 Fix typos in FlValue docs (flutter/engine#21875) * bb32446 Fix FlTextInputPlugin tear down (flutter/engine#22007) * 7a7804b Add "input shield" to capture pointer input for reinjection (flutter/engine#22067) * fe85f94 Update painting.dart (flutter/engine#22195) * 99cc50d [ios] Surface factory holds the canonical reference to the external view embedder (flutter/engine#22206)

…ne#21648)

googlebot added the cla: yes label Oct 7, 2020

auto-assign bot requested a review from jason-simmons October 7, 2020 12:40

knopp requested review from flar and removed request for jason-simmons October 7, 2020 12:52

liyuqian approved these changes Oct 26, 2020

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flar approved these changes Oct 26, 2020

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Use preTranslate when applying offset to matrix

1cfe7db

matrix.preTranslate(x,y) is identical to matrix.setConcat(matrix, SkMatrix::Translate(x,y));

knopp force-pushed the layer.use_pretranslate branch from 717b82f to 1cfe7db Compare October 27, 2020 22:15

chinmaygarde added the waiting for tree to go green This PR is approved and tested, but waiting for the tree to be green to land. label Oct 29, 2020

fluttergithubbot merged commit ed0f477 into flutter:master Oct 29, 2020

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Roll Engine from 073263e39d1d to fe85f946db04 (34 revisions) flutter/flutter#69343

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Roll engine from 073263e39d1d to fe85f946db04 (34 revisions) manual flutter/flutter#69347

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Roll Engine from 073263e39d1d to fe85f946db04 (34 revisions) flutter/flutter#69349

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Roll Engine from 073263e39d1d to 99cc50dfffab (35 revisions) flutter/flutter#69353

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Roll Engine from 073263e39d1d to 7d6180c3014a (37 revisions) flutter/flutter#69357

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Use preTranslate when applying offset to matrix (flutter#21648)

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Use preTranslate when applying offset to matrix #21648

Use preTranslate when applying offset to matrix #21648

knopp commented Oct 7, 2020

chinmaygarde commented Oct 22, 2020

liyuqian commented Oct 23, 2020

knopp commented Oct 23, 2020 •

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flar commented Oct 23, 2020

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liyuqian commented Oct 26, 2020

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Use preTranslate when applying offset to matrix #21648

Use preTranslate when applying offset to matrix #21648

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knopp commented Oct 7, 2020

Description

Related Issues

Tests

Checklist

Breaking Change

chinmaygarde commented Oct 22, 2020

liyuqian commented Oct 23, 2020

knopp commented Oct 23, 2020 • edited Loading

flar commented Oct 23, 2020

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knopp commented Oct 23, 2020 •

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