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* Copyright 2011 Google Inc.
* Use of this source code is governed by a BSD-style license that can be
* found in the LICENSE file.
#include "gm.h"
namespace skiagm {
/** Create a bitmap image suitable for testing SkBitmap::scrollRect().
* @param quarterWidth bitmap will be 4x this many pixels wide
* @param quarterHeight bitmap will be 4x this many pixels tall
* @param bitmap the bitmap data is written into this object
static void make_bitmap(int quarterWidth, int quarterHeight, SkBitmap *bitmap) {
SkPaint pRed, pWhite, pGreen, pBlue, pLine, pAlphaGray;
// Prepare bitmap, and a canvas that draws into it.
bitmap->allocN32Pixels(quarterWidth*4, quarterHeight*4);
SkCanvas canvas(*bitmap);
SkScalar w = SkIntToScalar(quarterWidth);
SkScalar h = SkIntToScalar(quarterHeight);
canvas.drawRectCoords( 0, 0, w*2, h*2, pRed);
canvas.drawRectCoords(w*2, 0, w*4, h*2, pGreen);
canvas.drawRectCoords( 0, h*2, w*2, h*4, pBlue);
canvas.drawRectCoords(w*2, h*2, w*4, h*4, pWhite);
canvas.drawRectCoords(w, h, w*3, h*3, pAlphaGray);
canvas.drawLine(w*2, 0, w*2, h*4, pLine);
canvas.drawLine( 0, h*2, w*4, h*2, pLine);
canvas.drawRectCoords(w, h, w*3, h*3, pLine);
class BitmapScrollGM : public GM {
bool fInited;
void init() {
if (fInited) {
fInited = true;
// Create the original bitmap.
make_bitmap(quarterWidth, quarterHeight, &origBitmap);
BitmapScrollGM() {
fInited = false;
SkString onShortName() override {
return SkString("bitmapscroll");
SkISize onISize() override {
return SkISize::Make(800, 600);
void onDraw(SkCanvas* canvas) override {
SkIRect scrollCenterRegion = SkIRect::MakeXYWH(
quarterWidth, quarterHeight, quarterWidth*2+1, quarterHeight*2+1);
int x = quarterWidth;
int y = quarterHeight;
int xSpacing = quarterWidth * 20;
int ySpacing = quarterHeight * 16;
// Draw left-hand text labels.
drawLabel(canvas, "scroll entire bitmap",
x, y, x, y + ySpacing);
drawLabel(canvas, "scroll part of bitmap",
x, y + ySpacing, x, y + ySpacing*2);
x += 30;
// Draw various permutations of scrolled bitmaps, scrolling a bit
// further each time.
draw9(canvas, x, y, NULL, quarterWidth*1/2, quarterHeight*1/2);
draw9(canvas, x, y+ySpacing, &scrollCenterRegion,
quarterWidth*1/2, quarterHeight*1/2);
x += xSpacing;
draw9(canvas, x, y, NULL, quarterWidth*3/2, quarterHeight*3/2);
draw9(canvas, x, y+ySpacing, &scrollCenterRegion,
quarterWidth*3/2, quarterHeight*3/2);
x += xSpacing;
draw9(canvas, x, y, NULL, quarterWidth*5/2, quarterHeight*5/2);
draw9(canvas, x, y+ySpacing, &scrollCenterRegion,
quarterWidth*5/2, quarterHeight*5/2);
x += xSpacing;
draw9(canvas, x, y, NULL, quarterWidth*9/2, quarterHeight*9/2);
draw9(canvas, x, y+ySpacing, &scrollCenterRegion,
quarterWidth*9/2, quarterHeight*9/2);
void drawLabel(SkCanvas* canvas, const char *text, int startX, int startY,
int endX, int endY) {
SkPaint paint;
SkPath path;
path.moveTo(SkIntToScalar(startX), SkIntToScalar(startY));
path.lineTo(SkIntToScalar(endX), SkIntToScalar(endY));
canvas->drawTextOnPath(text, strlen(text), path, NULL, paint);
/** Stamp out 9 copies of origBitmap, scrolled in each direction (and
* not scrolled at all).
void draw9(SkCanvas* canvas, int x, int y, SkIRect* subset,
int scrollX, int scrollY) {
for (int yMult=-1; yMult<=1; yMult++) {
for (int xMult=-1; xMult<=1; xMult++) {
// Figure out the (x,y) to draw this copy at
SkScalar bitmapX = SkIntToScalar(
x + quarterWidth * 5 * (xMult+1));
SkScalar bitmapY = SkIntToScalar(
y + quarterHeight * 5 * (yMult+1));
// Scroll a new copy of the bitmap, and then draw it.
// scrollRect() should always return true, even if it's a no-op
SkBitmap scrolledBitmap;
SkDEBUGCODE(bool copyToReturnValue = )origBitmap.copyTo(
&scrolledBitmap, origBitmap.colorType());
SkDEBUGCODE(bool scrollRectReturnValue = )scrolledBitmap.scrollRect(
subset, scrollX * xMult, scrollY * yMult);
canvas->drawBitmap(scrolledBitmap, bitmapX, bitmapY);
static const int quarterWidth = 10;
static const int quarterHeight = 14;
SkBitmap origBitmap;
static GM* MyFactory(void*) { return new BitmapScrollGM; }
static GMRegistry reg(MyFactory);