michael@0: 
michael@0: /*
michael@0:  * Copyright 2011 Google Inc.
michael@0:  *
michael@0:  * Use of this source code is governed by a BSD-style license that can be
michael@0:  * found in the LICENSE file.
michael@0:  */
michael@0: #include "SkBitmap.h"
michael@0: #include "SkRegion.h"
michael@0: 
michael@0: bool SkBitmap::scrollRect(const SkIRect* subset, int dx, int dy,
michael@0:                           SkRegion* inval) const
michael@0: {
michael@0:     if (this->isImmutable() || kUnknown_SkColorType == this->colorType()) {
michael@0:         return false;
michael@0:     }
michael@0: 
michael@0:     if (NULL != subset) {
michael@0:         SkBitmap tmp;
michael@0: 
michael@0:         return  this->extractSubset(&tmp, *subset) &&
michael@0:                 // now call again with no rectangle
michael@0:                 tmp.scrollRect(NULL, dx, dy, inval);
michael@0:     }
michael@0: 
michael@0:     int shift = this->bytesPerPixel() >> 1;
michael@0:     int width = this->width();
michael@0:     int height = this->height();
michael@0: 
michael@0:     // check if there's nothing to do
michael@0:     if ((dx | dy) == 0 || width <= 0 || height <= 0) {
michael@0:         if (NULL != inval) {
michael@0:             inval->setEmpty();
michael@0:         }
michael@0:         return true;
michael@0:     }
michael@0: 
michael@0:     // compute the inval region now, before we see if there are any pixels
michael@0:     if (NULL != inval) {
michael@0:         SkIRect r;
michael@0: 
michael@0:         r.set(0, 0, width, height);
michael@0:         // initial the region with the entire bounds
michael@0:         inval->setRect(r);
michael@0:         // do the "scroll"
michael@0:         r.offset(dx, dy);
michael@0: 
michael@0:         // check if we scrolled completely away
michael@0:         if (!SkIRect::Intersects(r, inval->getBounds())) {
michael@0:             // inval has already been updated...
michael@0:             return true;
michael@0:         }
michael@0: 
michael@0:         // compute the dirty area
michael@0:         inval->op(r, SkRegion::kDifference_Op);
michael@0:     }
michael@0: 
michael@0:     SkAutoLockPixels    alp(*this);
michael@0:     // if we have no pixels, just return (inval is already updated)
michael@0:     // don't call readyToDraw(), since we don't require a colortable per se
michael@0:     if (this->getPixels() == NULL) {
michael@0:         return true;
michael@0:     }
michael@0: 
michael@0:     char*       dst = (char*)this->getPixels();
michael@0:     const char* src = dst;
michael@0:     int         rowBytes = (int)this->rowBytes();    // need rowBytes to be signed
michael@0: 
michael@0:     if (dy <= 0) {
michael@0:         src -= dy * rowBytes;
michael@0:         height += dy;
michael@0:     } else {
michael@0:         dst += dy * rowBytes;
michael@0:         height -= dy;
michael@0:         // now jump src/dst to the last scanline
michael@0:         src += (height - 1) * rowBytes;
michael@0:         dst += (height - 1) * rowBytes;
michael@0:         // now invert rowbytes so we copy backwards in the loop
michael@0:         rowBytes = -rowBytes;
michael@0:     }
michael@0: 
michael@0:     if (dx <= 0) {
michael@0:         src -= dx << shift;
michael@0:         width += dx;
michael@0:     } else {
michael@0:         dst += dx << shift;
michael@0:         width -= dx;
michael@0:     }
michael@0: 
michael@0:     // If the X-translation would push it completely beyond the region,
michael@0:     // then there's nothing to draw.
michael@0:     if (width <= 0) {
michael@0:         return true;
michael@0:     }
michael@0: 
michael@0:     width <<= shift;    // now width is the number of bytes to move per line
michael@0:     while (--height >= 0) {
michael@0:         memmove(dst, src, width);
michael@0:         dst += rowBytes;
michael@0:         src += rowBytes;
michael@0:     }
michael@0: 
michael@0:     this->notifyPixelsChanged();
michael@0:     return true;
michael@0: }