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
5 REG_FIDDLE(Canvas_saveLayer_4, 256, 256, false, 3) {
draw(SkCanvas * canvas)6 void 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