flow/paint_utils.cc

// Copyright 2013 The Flutter Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

#include "flutter/flow/paint_utils.h"

#include <stdlib.h>

#include "third_party/skia/include/core/SkBitmap.h"
#include "third_party/skia/include/core/SkImage.h"

namespace flutter {

namespace {

std::shared_ptr<DlColorSource> CreateCheckerboardShader(SkColor c1,
                                                        SkColor c2,
                                                        int size) {
  SkBitmap bm;
  bm.allocN32Pixels(2 * size, 2 * size);
  bm.eraseColor(c1);
  bm.eraseArea(SkIRect::MakeLTRB(0, 0, size, size), c2);
  bm.eraseArea(SkIRect::MakeLTRB(size, size, 2 * size, 2 * size), c2);
  auto image = DlImage::Make(SkImages::RasterFromBitmap(bm));
  return std::make_shared<DlImageColorSource>(
      image, DlTileMode::kRepeat, DlTileMode::kRepeat,
      DlImageSampling::kNearestNeighbor);
}

}  // anonymous namespace

void DrawCheckerboard(DlCanvas* canvas, const SkRect& rect) {
  // Draw a checkerboard
  canvas->Save();
  canvas->ClipRect(rect, DlCanvas::ClipOp::kIntersect, false);

  // Secure random number generation isn't needed here.
  // NOLINTBEGIN(clang-analyzer-security.insecureAPI.rand)
  auto checkerboard_color =
      SkColorSetARGB(64, rand() % 256, rand() % 256, rand() % 256);
  // NOLINTEND(clang-analyzer-security.insecureAPI.rand)

  DlPaint paint;
  paint.setColorSource(
      CreateCheckerboardShader(checkerboard_color, 0x00000000, 12));
  canvas->DrawPaint(paint);
  canvas->Restore();

  // Stroke the drawn area
  DlPaint debug_paint;
  debug_paint.setStrokeWidth(8);
  debug_paint.setColor(DlColor(SkColorSetA(checkerboard_color, 255)));
  debug_paint.setDrawStyle(DlDrawStyle::kStroke);
  canvas->DrawRect(rect, debug_paint);
}

}  // namespace flutter