1/*
2 * Copyright 2014 Google Inc.
3 *
4 * Use of this source code is governed by a BSD-style license that can be
5 * found in the LICENSE file.
6 */
7
8#include "gm.h"
9#include "sk_tool_utils.h"
10#include "SkCanvas.h"
11#include "SkPaint.h"
12#include "SkRandom.h"
13#include "SkSurface.h"
14
15#if SK_SUPPORT_GPU
16
17namespace skiagm {
18
19/*
20 * This GM exercises SkCanvas::discard() by creating an offscreen SkSurface and repeatedly
21 * discarding it, drawing to it, and then drawing it to the main canvas.
22 */
23class DiscardGM : public GM {
24
25public:
26    DiscardGM() {
27    }
28
29protected:
30    SkString onShortName() override {
31        return SkString("discard");
32    }
33
34    SkISize onISize() override {
35        return SkISize::Make(100, 100);
36    }
37
38    void onDraw(SkCanvas* canvas) override {
39        GrContext* context = canvas->getGrContext();
40        if (nullptr == context) {
41            return;
42        }
43
44        SkISize size = this->getISize();
45        size.fWidth /= 10;
46        size.fHeight /= 10;
47        SkImageInfo info = SkImageInfo::MakeN32Premul(size);
48        auto surface = SkSurface::MakeRenderTarget(context, SkBudgeted::kNo, info);
49        if (nullptr == surface) {
50            return;
51        }
52
53        canvas->clear(SK_ColorBLACK);
54
55        SkRandom rand;
56        for (int x = 0; x < 10; ++x) {
57            for (int y = 0; y < 10; ++y) {
58              surface->getCanvas()->discard();
59              // Make something that isn't too close to the background color, black.
60              SkColor color = sk_tool_utils::color_to_565(rand.nextU() | 0xFF404040);
61              switch (rand.nextULessThan(3)) {
62                  case 0:
63                      surface->getCanvas()->drawColor(color);
64                      break;
65                  case 1:
66                      surface->getCanvas()->clear(color);
67                      break;
68                  case 2:
69                      SkPaint paint;
70                      paint.setShader(SkShader::MakeColorShader(color));
71                      surface->getCanvas()->drawPaint(paint);
72                      break;
73              }
74              surface->draw(canvas, 10.f*x, 10.f*y, nullptr);
75            }
76        }
77
78        surface->getCanvas()->discard();
79    }
80
81private:
82    typedef GM INHERITED;
83};
84
85//////////////////////////////////////////////////////////////////////////////
86
87DEF_GM(return new DiscardGM;)
88
89} // end namespace
90
91#endif
92