1#Topic Automatic_Canvas_Restore
2
3#Subtopic Overview
4    #Subtopic Subtopics
5    #Populate
6    ##
7##
8
9#Class SkAutoCanvasRestore
10
11Stack helper class calls SkCanvas::restoreToCount() when SkAutoCanvasRestore
12goes out of scope. Use this to guarantee that the canvas is restored to a known
13state.
14
15#Subtopic Constructors
16#Populate
17##
18
19#Subtopic Member_Functions
20#Populate
21##
22
23#Method SkAutoCanvasRestore(SkCanvas* canvas, bool doSave)
24
25#Line # preserves Canvas save count ##
26Preserves Canvas save count. Optionally saves Canvas_Clip and Canvas_Matrix.
27
28#Param canvas  Canvas to guard ##
29#Param doSave  call SkCanvas::save() ##
30
31#Return utility to restore Canvas state on destructor ##
32
33#Example
34#Height 128
35    SkPaint p;
36    p.setAntiAlias(true);
37    p.setTextSize(64);
38    for (SkScalar sx : { -1, 1 } ) {
39        for (SkScalar sy : { -1, 1 } ) {
40            SkAutoCanvasRestore autoRestore(canvas, true);
41            SkMatrix m = SkMatrix::MakeAll(sx, 1, 96,    0, sy, 64,   0, 0, 1);
42            canvas->concat(m);
43            canvas->drawString("R", 0, 0, p);
44        }
45    }
46##
47
48#SeeAlso SkCanvas::save SkCanvas::restore
49
50##
51
52#Method ~SkAutoCanvasRestore()
53
54#Line # restores Canvas to saved state ##
55Restores Canvas to saved state. Destructor is called when container goes out of
56scope.
57
58#NoExample
59##
60
61#SeeAlso SkCanvas::save SkCanvas::restore
62
63##
64
65#Method void restore()
66
67#Line # restores Canvas to saved state ##
68Restores Canvas to saved state immediately. Subsequent calls and
69~SkAutoCanvasRestore have no effect.
70
71#Example
72for (bool callRestore : { false, true } ) {
73    for (bool saveCanvas : {false, true} ) {
74        SkAutoCanvasRestore autoRestore(canvas, saveCanvas);
75        if (!saveCanvas) {
76            canvas->save();
77        }
78        SkDebugf("saveCanvas: %s  before restore: %d\n",
79               saveCanvas ? "true" : "false", canvas->getSaveCount());
80        if (callRestore) autoRestore.restore();
81        SkDebugf("saveCanvas: %s  after restore: %d\n",
82               saveCanvas ? "true" : "false", canvas->getSaveCount());
83    }
84}
85SkDebugf("final count: %d\n", canvas->getSaveCount());
86#StdOut
87saveCanvas: false  before restore: 2
88saveCanvas: false  after restore: 2
89saveCanvas: true  before restore: 2
90saveCanvas: true  after restore: 2
91saveCanvas: false  before restore: 2
92saveCanvas: false  after restore: 1
93saveCanvas: true  before restore: 2
94saveCanvas: true  after restore: 1
95final count: 1
96##
97##
98
99#SeeAlso SkCanvas::save SkCanvas::restore
100
101##
102
103#Class SkAutoCanvasRestore ##
104
105#Topic Automatic_Canvas_Restore ##
106