Fix SkXfermodeImageFilter when an input is cropped out.

src/effects/SkXfermodeImageFilter.cpp

 /*
  * Copyright 2013 The Android Open Source Project
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 #include "SkXfermodeImageFilter.h"
 #include "SkCanvas.h"
 #include "SkDevice.h"
@@ skipping 35 matching lines @@
                                             const SkBitmap& src,
                                             const Context& ctx,
                                             SkBitmap* dst,
                                             SkIPoint* offset) const {
     SkBitmap background = src, foreground = src;
     SkImageFilter* backgroundInput = getInput(0);
     SkImageFilter* foregroundInput = getInput(1);
     SkIPoint backgroundOffset = SkIPoint::Make(0, 0);
     if (backgroundInput &&
         !backgroundInput->filterImage(proxy, src, ctx, &background, &backgroundOffset)) {
-        return false;
+        background.reset();
     }
     SkIPoint foregroundOffset = SkIPoint::Make(0, 0);
     if (foregroundInput &&
         !foregroundInput->filterImage(proxy, src, ctx, &foreground, &foregroundOffset)) {
-        return false;
+        foreground.reset();
     }
 
     SkIRect bounds, foregroundBounds;
     if (!applyCropRect(ctx, foreground, foregroundOffset, &foregroundBounds)) {
+        foregroundBounds.setEmpty();
+        foreground.reset();
+    }
+    if (!applyCropRect(ctx, background, backgroundOffset, &bounds)) {
+        bounds.setEmpty();
+        background.reset();
+    }
+    bounds.join(foregroundBounds);
+    if (bounds.isEmpty()) {
         return false;
     }
-    if (!applyCropRect(ctx, background, backgroundOffset, &bounds)) {
-        return false;
-    }
-    bounds.join(foregroundBounds);
 
     SkAutoTUnref<SkBaseDevice> device(proxy->createDevice(bounds.width(), bounds.height()));
     if (NULL == device.get()) {
         return false;
     }
     SkCanvas canvas(device);
     canvas.translate(SkIntToScalar(-bounds.left()), SkIntToScalar(-bounds.top()));
     SkPaint paint;
     paint.setXfermodeMode(SkXfermode::kSrc_Mode);
     canvas.drawBitmap(background, SkIntToScalar(backgroundOffset.fX),
                       SkIntToScalar(backgroundOffset.fY), &paint);
     paint.setXfermode(fMode);
     canvas.drawBitmap(foreground, SkIntToScalar(foregroundOffset.fX),
                       SkIntToScalar(foregroundOffset.fY), &paint);
     canvas.clipRect(SkRect::Make(foregroundBounds), SkRegion::kDifference_Op);
     paint.setColor(SK_ColorTRANSPARENT);
     canvas.drawPaint(paint);
     *dst = device->accessBitmap(false);
     offset->fX = bounds.left();
     offset->fY = bounds.top();
     return true;
 }
 
 #if SK_SUPPORT_GPU
 
+bool SkXfermodeImageFilter::canFilterImageGPU() const {
+    return fMode && fMode->asNewEffect(NULL, NULL) && !cropRectIsSet();
+}
+
 bool SkXfermodeImageFilter::filterImageGPU(Proxy* proxy,
                                            const SkBitmap& src,
                                            const Context& ctx,
                                            SkBitmap* result,
                                            SkIPoint* offset) const {
     SkBitmap background = src;
     SkIPoint backgroundOffset = SkIPoint::Make(0, 0);
     if (getInput(0) && !getInput(0)->getInputResultGPU(proxy, src, ctx, &background,
                                                        &backgroundOffset)) {
-        return false;
+        return onFilterImage(proxy, src, ctx, result, offset);
     }
     GrTexture* backgroundTex = background.getTexture();
     SkBitmap foreground = src;
     SkIPoint foregroundOffset = SkIPoint::Make(0, 0);
     if (getInput(1) && !getInput(1)->getInputResultGPU(proxy, src, ctx, &foreground,
                                                        &foregroundOffset)) {
-        return false;
+        return onFilterImage(proxy, src, ctx, result, offset);
     }
     GrTexture* foregroundTex = foreground.getTexture();
     GrContext* context = foregroundTex->getContext();
 
     GrEffectRef* xferEffect = NULL;
 
     GrTextureDesc desc;
     desc.fFlags = kRenderTarget_GrTextureFlagBit | kNoStencil_GrTextureFlagBit;
     desc.fWidth = src.width();
     desc.fHeight = src.height();
     desc.fConfig = kSkia8888_GrPixelConfig;
 
     GrAutoScratchTexture ast(context, desc);
     SkAutoTUnref<GrTexture> dst(ast.detach());
 
     GrContext::AutoRenderTarget art(context, dst->asRenderTarget());
 
-    SkXfermode::Coeff sm, dm;
-    if (!SkXfermode::AsNewEffectOrCoeff(fMode, &xferEffect, &sm, &dm, backgroundTex)) {
+    if (!fMode || !fMode->asNewEffect(&xferEffect, backgroundTex)) {
+        // canFilterImageGPU() should've taken care of this
+        SkASSERT(false);
         return false;
     }
 
     SkMatrix foregroundMatrix = GrEffect::MakeDivByTextureWHMatrix(foregroundTex);
     foregroundMatrix.preTranslate(SkIntToScalar(backgroundOffset.fX-foregroundOffset.fX),
                                   SkIntToScalar(backgroundOffset.fY-foregroundOffset.fY));
 
 
     SkRect srcRect;
     src.getBounds(&srcRect);
-    if (NULL != xferEffect) {
-        GrPaint paint;
-        paint.addColorTextureEffect(foregroundTex, foregroundMatrix);
-        paint.addColorEffect(xferEffect)->unref();
-        context->drawRect(paint, srcRect);
-    } else {
-        GrPaint backgroundPaint;
-        SkMatrix backgroundMatrix = GrEffect::MakeDivByTextureWHMatrix(backgroundTex);
-        backgroundPaint.addColorTextureEffect(backgroundTex, backgroundMatrix);
-        context->drawRect(backgroundPaint, srcRect);
 
-        GrPaint foregroundPaint;
-        foregroundPaint.setBlendFunc(sk_blend_to_grblend(sm), sk_blend_to_grblend(dm));
-        foregroundPaint.addColorTextureEffect(foregroundTex, foregroundMatrix);
-        context->drawRect(foregroundPaint, srcRect);
-    }
+    GrPaint paint;
+    paint.addColorTextureEffect(foregroundTex, foregroundMatrix);
+    paint.addColorEffect(xferEffect)->unref();
+    context->drawRect(paint, srcRect);
+
     offset->fX = backgroundOffset.fX;
     offset->fY = backgroundOffset.fY;
     WrapTexture(dst, src.width(), src.height(), result);
     return true;
 }
 
 #endif