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Add a GM that reproduces layout test failures with my new xfermode code.

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Inspired by https://storage.googleapis.com/chromium-layout-test-archives/linux_blink_rel/69169/layout-test-results/results.html

I think the root cause is overflow.

Also, adds tests for Sk16b::operator<().  It wasn't wrong, but it was suspect
(used in all three of these xfermode implementations) and so it's best to have
tests.

BUG=skia:

Review URL: https://codereview.chromium.org/1228393006
This commit is contained in:
mtklein 2015-07-13 12:06:33 -07:00 committed by Commit bot
parent cd8c499f2e
commit e20633ed26
2 changed files with 56 additions and 2 deletions
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52
gm/buggy_blend_modes.cpp Normal file
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@ -0,0 +1,52 @@
/*
* Copyright 2015 Google Inc.
*
* Use of this source code is governed by a BSD-style license that can be
* found in the LICENSE file.
*/
#include "SkCanvas.h"
#include "SkGradientShader.h"
#include "gm.h"
// This GM reproduces what I think are overflow bugs in the CPU implementations of a
// couple xfermodes. I've marked non-obvious keys to reproducing the bug // Essential!
DEF_SIMPLE_GM(buggy_blend_modes, canvas, 800, 200) {
const auto tiling = SkShader::kClamp_TileMode;
const auto flags = SkGradientShader::kInterpolateColorsInPremul_Flag; // Essential!
SkAutoTUnref<SkShader> cyanH, magentaV;
{
SkPoint pts[] = { {0,0}, {200, 0} };
SkColor colors[] = { 0x00000000, 0xFF00FFFF };
cyanH.reset(
SkGradientShader::CreateLinear(pts, colors, nullptr, 2, tiling, flags, nullptr));
}
{
SkPoint pts[] = { {0,0}, {0, 200} };
SkColor colors[] = { 0x00000000, 0xFFFF00FF };
magentaV.reset(
SkGradientShader::CreateLinear(pts, colors, nullptr, 2, tiling, flags, nullptr));
}
SkXfermode::Mode modes[] = {
SkXfermode::kDarken_Mode, // Looks ok?
SkXfermode::kHardLight_Mode, // Definitely wrong.
SkXfermode::kLighten_Mode, // Definitely wrong.
SkXfermode::kOverlay_Mode, // Same code as kHardLight_Mode.
};
canvas->clear(SK_ColorWHITE);
for (auto mode : modes) {
canvas->saveLayer(nullptr, nullptr); // Essential!
SkPaint h, v;
h.setShader(cyanH);
v.setShader(magentaV);
v.setXfermodeMode(mode);
canvas->drawRect(SkRect::MakeWH(200,200), h);
canvas->drawRect(SkRect::MakeWH(200,200), v);
canvas->restore();
canvas->translate(200, 0);
}
}

6
tests/SkNxTest.cpp
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@ -133,11 +133,13 @@ DEF_TEST(SkNi, r) {
test_Ni<8, int>(r);
}
DEF_TEST(SkNi_min, r) {
DEF_TEST(SkNi_min_lt, r) {
// Exhaustively check the 8x8 bit space.
for (int a = 0; a < (1<<8); a++) {
for (int b = 0; b < (1<<8); b++) {
REPORTER_ASSERT(r, Sk16b::Min(Sk16b(a), Sk16b(b)).kth<0>() == SkTMin(a, b));
Sk16b aw(a), bw(b);
REPORTER_ASSERT(r, Sk16b::Min(aw, bw).kth<0>() == SkTMin(a, b));
REPORTER_ASSERT(r, !(aw < bw).kth<0>() == !(a < b));
}}
// Exhausting the 16x16 bit space is kind of slow, so only do that in release builds.