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 "SkCanvas.h"
10#include "SkColorShader.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        SkSurface* surface = SkSurface::NewRenderTarget(context, SkBudgeted::kNo, info);
49
50        if (nullptr == surface) {
51            return;
52        }
53
54        canvas->clear(SK_ColorBLACK);
55
56        SkRandom rand;
57        for (int x = 0; x < 10; ++x) {
58            for (int y = 0; y < 10; ++y) {
59              surface->getCanvas()->discard();
60              // Make something that isn't too close to the background color, black.
61              SkColor color = sk_tool_utils::color_to_565(rand.nextU() | 0xFF404040);
62              switch (rand.nextULessThan(3)) {
63                  case 0:
64                      surface->getCanvas()->drawColor(color);
65                      break;
66                  case 1:
67                      surface->getCanvas()->clear(color);
68                      break;
69                  case 2:
70                      SkColorShader shader(color);
71                      SkPaint paint;
72                      paint.setShader(&shader);
73                      surface->getCanvas()->drawPaint(paint);
74                      break;
75              }
76              surface->draw(canvas, 10.f*x, 10.f*y, nullptr);
77            }
78        }
79
80        surface->getCanvas()->discard();
81        surface->unref();
82    }
83
84private:
85    typedef GM INHERITED;
86};
87
88//////////////////////////////////////////////////////////////////////////////
89
90DEF_GM(return new DiscardGM;)
91
92} // end namespace
93
94#endif
95