text: /*
   * Copyright 2017 Google Inc.
   *
   * Use of this source code is governed by a BSD-style license that can be
   * found in the LICENSE file.
   */
  
  #include "SkTypes.h"
  
  #include "SkCanvas.h"
  #include "SkSurface.h"
  
  #if SK_SUPPORT_GPU
  
  #include "GrContext.h"
  #include "GrTest.h"
  #include "Test.h"
  
  static SkBitmap read_pixels(sk_sp<SkSurface> surface) {
      SkBitmap bmp;
      bmp.allocN32Pixels(surface->width(), surface->height());
      if (!surface->getCanvas()->readPixels(bmp, 0, 0)) {
          SkDebugf("readPixels failed\n");
      }
      return bmp;
  }
  
  static sk_sp<SkSurface> make_surface(GrContext* context) {
      SkImageInfo info = SkImageInfo::Make(50, 50, kRGBA_8888_SkColorType, kPremul_SkAlphaType);
      return SkSurface::MakeRenderTarget(context, SkBudgeted::kNo, info, 4,
                                         kBottomLeft_GrSurfaceOrigin, nullptr);
  }
  
  // Tests that readPixels returns up-to-date results. Demonstrates a bug on Galaxy S6
  // (Mali T760), in MSAA mode.
  DEF_GPUTEST_FOR_RENDERING_CONTEXTS(skbug6653, reporter, ctxInfo) {
      GrContext* ctx = ctxInfo.grContext();
      SkRect rect = SkRect::MakeWH(50, 50);
  
      SkPaint paint;
      paint.setColor(SK_ColorWHITE);
      paint.setStrokeWidth(5);
      paint.setStyle(SkPaint::kStroke_Style);
  
      // The one device that fails this test (Galaxy S6) does so in a flaky fashion. Trying many
      // times makes it more likely to fail. Also, interacting with the phone (eg swiping between
      // different home screens) while the test is running makes it fail close to 100%.
      static const int kNumIterations = 50;
  
      for (int i = 0; i < kNumIterations; ++i) {
          auto s0 = make_surface(ctx);
          if (!s0) {
              // MSAA may not be supported
              return;
          }
  
          auto s1 = make_surface(ctx);
          s1->getCanvas()->clear(SK_ColorBLACK);
          s1->getCanvas()->drawOval(rect, paint);
          SkBitmap b1 = read_pixels(s1);
          s1 = nullptr;
  
          // The bug requires that all three of the following surfaces are cleared to the same color
          auto s2 = make_surface(ctx);
          s2->getCanvas()->clear(SK_ColorBLUE);
          SkBitmap b2 = read_pixels(s2);
          s2 = nullptr;
  
          auto s3 = make_surface(ctx);
          s3->getCanvas()->clear(SK_ColorBLUE);
          SkBitmap b3 = read_pixels(s3);
          s0->getCanvas()->drawBitmap(b3, 0, 0);
          s3 = nullptr;
  
          auto s4 = make_surface(ctx);
          s4->getCanvas()->clear(SK_ColorBLUE);
          s4->getCanvas()->drawOval(rect, paint);
  
          // When this fails, b4 will "succeed", but return an empty bitmap (containing just the
          // clear color). Regardless, b5 will contain the oval that was just drawn, so diffing the
          // two bitmaps tests for the failure case.
          SkBitmap b4 = read_pixels(s4);
          SkBitmap b5 = read_pixels(s4);
  
          bool match = true;
          for (int y = 0; y < b4.height() && match; ++y) {
              for (int x = 0; x < b4.width() && match; ++x) {
                  uint32_t pixelA = *b4.getAddr32(x, y);
                  uint32_t pixelB = *b5.getAddr32(x, y);
                  if (pixelA != pixelB) {
                      match = false;
                  }
              }
          }
  
          REPORTER_ASSERT(reporter, match);
      }
  }
  
  #endif
  