1 #include "SkBitmap.h"
2 #include "SkRegion.h"
3
scrollRect(const SkIRect * subset,int dx,int dy,SkRegion * inval) const4 bool SkBitmap::scrollRect(const SkIRect* subset, int dx, int dy,
5 SkRegion* inval) const
6 {
7 if (NULL != subset) {
8 SkBitmap tmp;
9
10 return this->extractSubset(&tmp, *subset) &&
11 // now call again with no rectangle
12 tmp.scrollRect(NULL, dx, dy, inval);
13 }
14
15 int shift;
16
17 switch (this->config()) {
18 case kIndex8_Config:
19 case kA8_Config:
20 shift = 0;
21 break;
22 case kARGB_4444_Config:
23 case kRGB_565_Config:
24 shift = 1;
25 break;
26 case kARGB_8888_Config:
27 shift = 2;
28 break;
29 default:
30 // can't scroll this config
31 return false;
32 }
33
34 int width = this->width();
35 int height = this->height();
36
37 // check if there's nothing to do
38 if ((dx | dy) == 0 || width <= 0 || height <= 0) {
39 if (NULL != inval) {
40 inval->setEmpty();
41 }
42 return true;
43 }
44
45 // compute the inval region now, before we see if there are any pixels
46 if (NULL != inval) {
47 SkIRect r;
48
49 r.set(0, 0, width, height);
50 // initial the region with the entire bounds
51 inval->setRect(r);
52 // do the "scroll"
53 r.offset(dx, dy);
54
55 // check if we scrolled completely away
56 if (!SkIRect::Intersects(r, inval->getBounds())) {
57 // inval has already been updated...
58 return true;
59 }
60
61 // compute the dirty area
62 inval->op(r, SkRegion::kDifference_Op);
63 }
64
65 SkAutoLockPixels alp(*this);
66 // if we have no pixels, just return (inval is already updated)
67 // don't call readyToDraw(), since we don't require a colortable per se
68 if (this->getPixels() == NULL) {
69 return true;
70 }
71
72 // if we get this far, then we need to shift the pixels
73
74 char* dst = (char*)this->getPixels();
75 const char* src = dst;
76 int rowBytes = this->rowBytes(); // need rowBytes to be signed
77
78 if (dy <= 0) {
79 src -= dy * rowBytes;
80 height += dy;
81 } else {
82 dst += dy * rowBytes;
83 height -= dy;
84 // now jump src/dst to the last scanline
85 src += (height - 1) * rowBytes;
86 dst += (height - 1) * rowBytes;
87 // now invert rowbytes so we copy backwards in the loop
88 rowBytes = -rowBytes;
89 }
90
91 if (dx <= 0) {
92 src -= dx << shift;
93 width += dx;
94 } else {
95 dst += dx << shift;
96 width -= dx;
97 }
98
99 width <<= shift; // now width is the number of bytes to move per line
100 while (--height >= 0) {
101 memmove(dst, src, width);
102 dst += rowBytes;
103 src += rowBytes;
104 }
105 return true;
106 }
107
108