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