1
2 /*
3 * Copyright 2011 Google Inc.
4 *
5 * Use of this source code is governed by a BSD-style license that can be
6 * found in the LICENSE file.
7 */
8 #include "SkBitmap.h"
9 #include "SkRegion.h"
10
scrollRect(const SkIRect * subset,int dx,int dy,SkRegion * inval) const11 bool SkBitmap::scrollRect(const SkIRect* subset, int dx, int dy,
12 SkRegion* inval) const
13 {
14 if (NULL != subset) {
15 SkBitmap tmp;
16
17 return this->extractSubset(&tmp, *subset) &&
18 // now call again with no rectangle
19 tmp.scrollRect(NULL, dx, dy, inval);
20 }
21
22 int shift;
23
24 switch (this->config()) {
25 case kIndex8_Config:
26 case kA8_Config:
27 shift = 0;
28 break;
29 case kARGB_4444_Config:
30 case kRGB_565_Config:
31 shift = 1;
32 break;
33 case kARGB_8888_Config:
34 shift = 2;
35 break;
36 default:
37 // can't scroll this config
38 return false;
39 }
40
41 int width = this->width();
42 int height = this->height();
43
44 // check if there's nothing to do
45 if ((dx | dy) == 0 || width <= 0 || height <= 0) {
46 if (NULL != inval) {
47 inval->setEmpty();
48 }
49 return true;
50 }
51
52 // compute the inval region now, before we see if there are any pixels
53 if (NULL != inval) {
54 SkIRect r;
55
56 r.set(0, 0, width, height);
57 // initial the region with the entire bounds
58 inval->setRect(r);
59 // do the "scroll"
60 r.offset(dx, dy);
61
62 // check if we scrolled completely away
63 if (!SkIRect::Intersects(r, inval->getBounds())) {
64 // inval has already been updated...
65 return true;
66 }
67
68 // compute the dirty area
69 inval->op(r, SkRegion::kDifference_Op);
70 }
71
72 SkAutoLockPixels alp(*this);
73 // if we have no pixels, just return (inval is already updated)
74 // don't call readyToDraw(), since we don't require a colortable per se
75 if (this->getPixels() == NULL) {
76 return true;
77 }
78
79 char* dst = (char*)this->getPixels();
80 const char* src = dst;
81 int rowBytes = this->rowBytes(); // need rowBytes to be signed
82
83 if (dy <= 0) {
84 src -= dy * rowBytes;
85 height += dy;
86 } else {
87 dst += dy * rowBytes;
88 height -= dy;
89 // now jump src/dst to the last scanline
90 src += (height - 1) * rowBytes;
91 dst += (height - 1) * rowBytes;
92 // now invert rowbytes so we copy backwards in the loop
93 rowBytes = -rowBytes;
94 }
95
96 if (dx <= 0) {
97 src -= dx << shift;
98 width += dx;
99 } else {
100 dst += dx << shift;
101 width -= dx;
102 }
103
104 // If the X-translation would push it completely beyond the region,
105 // then there's nothing to draw.
106 if (width <= 0) {
107 return true;
108 }
109
110 width <<= shift; // now width is the number of bytes to move per line
111 while (--height >= 0) {
112 memmove(dst, src, width);
113 dst += rowBytes;
114 src += rowBytes;
115 }
116 return true;
117 }
118