1// Copyright 2020 Google LLC.
2// Use of this source code is governed by a BSD-style license that can be found in the LICENSE file.
3#include "tools/fiddle/examples.h"
4// HASH=7d3751e82d1b6ec328ffa3d6f48ca831
5REG_FIDDLE(Canvas_saveLayer_4, 256, 256, false, 3) {
6void draw(SkCanvas* canvas) {
7    SkPaint pRed;
8    pRed.setColor(SK_ColorRED);
9
10    SkPaint pSolidBlue;
11    pSolidBlue.setColor(SK_ColorBLUE);
12
13    SkPaint pThirtyBlue;
14    pThirtyBlue.setColor(SK_ColorBLUE);
15    pThirtyBlue.setAlphaf(0.3);
16
17    SkPaint alpha;
18    alpha.setAlphaf(0.3);
19
20    // First row: Draw two opaque red rectangles into the 0th layer. Then draw two blue
21    // rectangles overlapping the red, one is solid, the other is 30% transparent.
22    canvas->drawRect(SkRect::MakeLTRB(10, 10, 60, 60), pRed);
23    canvas->drawRect(SkRect::MakeLTRB(150, 10, 200, 60), pRed);
24
25    canvas->drawRect(SkRect::MakeLTRB(30, 10, 80, 60), pSolidBlue);
26    canvas->drawRect(SkRect::MakeLTRB(170, 10, 220, 60), pThirtyBlue);
27
28    // Second row: Draw two opaque red rectangles into the 0th layer. Then save a new layer;
29    // when the 1st layer gets merged onto the 0th layer (i.e. when restore() is called), it will
30    // use the provided paint to do so. In this case, the paint is set to have 30% opacity, but
31    // it could also have things set like blend modes or image filters.
32    canvas->drawRect(SkRect::MakeLTRB(10, 70, 60, 120), pRed);
33    canvas->drawRect(SkRect::MakeLTRB(150, 70, 200, 120), pRed);
34
35    canvas->saveLayer(nullptr, &alpha);
36
37    // In the 1st layer, draw the same blue overlapping rectangles as in the first row. Notice in
38    // the final output, we have two different shades of purple. The layer's alpha made the
39    // opaque blue rectangle transparent, and it made the transparent blue rectangle even more so
40    canvas->drawRect(SkRect::MakeLTRB(30, 70, 80, 120), pSolidBlue);
41    canvas->drawRect(SkRect::MakeLTRB(170, 70, 220, 120), pThirtyBlue);
42
43    canvas->restore();
44
45    // Third row: save the layer first, before drawing the two red rectangle, followed by the
46    // overlapping blue rectangles. Notice that the blue overwrites the red in the same way as
47    // the first row because the alpha of the layer is not applied until the layer is restored.
48    canvas->saveLayer(nullptr, &alpha);
49
50    canvas->drawRect(SkRect::MakeLTRB(10, 130, 60, 180), pRed);
51    canvas->drawRect(SkRect::MakeLTRB(150, 130, 200, 180), pRed);
52
53    canvas->drawRect(SkRect::MakeLTRB(30, 130, 80, 180), pSolidBlue);
54    canvas->drawRect(SkRect::MakeLTRB(170, 130, 220, 180), pThirtyBlue);
55
56    canvas->restore();
57}
58}  // END FIDDLE
59