tunnel down texture-size-constraint to imagefilters

src/image/SkImage_Gpu.cpp

Index: src/image/SkImage_Gpu.cpp
diff --git a/src/image/SkImage_Gpu.cpp b/src/image/SkImage_Gpu.cpp
index b1f78513ecfe394e1f1a1d6ba5e241add7426836..4cbc2fef0347d2dce4394be2116e20c6254d3ff4 100644
--- a/src/image/SkImage_Gpu.cpp
+++ b/src/image/SkImage_Gpu.cpp
@@ -24,7 +24,13 @@ SkImage_Gpu::SkImage_Gpu(int w, int h, uint32_t uniqueID, SkAlphaType at, GrText
     , fAlphaType(at)
     , fBudgeted(budgeted)
     , fAddedRasterVersionToCache(false)
-    {}
+{
+    // At the moment, we can't handle general transformations on textures (e.g. tiling,
+    // mip/filtering) unless they are exactly sized to match the "logical" size (image size).
+    // Hence these asserts.
+    SkASSERT(tex->width() == w);
+    SkASSERT(tex->height() == h);
+}
 
 SkImage_Gpu::~SkImage_Gpu() {
     if (fAddedRasterVersionToCache.load()) {
@@ -187,10 +193,10 @@ SkImage* SkImage_Gpu::onNewSubset(const SkIRect& subset) const {
 #include "SkImageFilter.h"
 
 class SkGpuImageFilterProxy : public SkImageFilter::Proxy {
-    GrContext* fCtx;
-
 public:
-    SkGpuImageFilterProxy(GrContext* ctx) : fCtx(ctx) {}
+    SkGpuImageFilterProxy(GrContext* ctx, bool requireExactTexSize)
+        : INHERITED(requireExactTexSize), fCtx(ctx)
+    {}
 
     SkBaseDevice* createDevice(int width, int height) override {
         GrSurfaceDesc desc;
@@ -216,6 +222,11 @@ public:
         return filter->canFilterImageGPU() &&
                filter->filterImageGPU(this, src, ctx, dst, offset);
     }
+
+private:
+    GrContext* fCtx;
+
+    typedef Proxy INHERITED;
 };
 
 static SkIRect compute_fast_ibounds(SkImageFilter* filter, const SkIRect& srcBounds) {
@@ -233,10 +244,14 @@ SkImage* SkImage_Gpu::onApplyFilter(SkImageFilter* filter, SkIPoint* offsetResul
         SkBitmap src;
         GrWrapTextureInBitmap(fTexture, this->width(), this->height(), this->isOpaque(), &src);
 
-        const SkIRect clipBounds = srcBounds;
-        SkGpuImageFilterProxy proxy(fTexture->getContext());
+        // Since we want to return an image that wraps the filter's texture, and our clients
+        // assume (at the moment) that the image can be scaled/tiled etc., we must have an exact
+        // sized texture (matching the image's logical size). Hence we pass true to the Proxy's
+        // constructor.
+        const bool kRequireExactTexSize = true;
+        SkGpuImageFilterProxy proxy(fTexture->getContext(), kRequireExactTexSize);
         SkAutoTUnref<SkImageFilter::Cache> cache(SkGpuDevice::NewImageFilterCache());
-        SkImageFilter::Context ctx(SkMatrix::I(), clipBounds, cache);
+        SkImageFilter::Context ctx(SkMatrix::I(), srcBounds, cache);
 
         SkBitmap dst;
         if (!filter->filterImage(&proxy, src, ctx, &dst, offsetResult)) {