use drawRect when drawing a bitmap with anti-aliasing on a non-msaa target

src/gpu/SkGpuDevice.cpp

 /*
  * 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 "SkGpuDevice.h"
 
 #include "effects/GrBicubicEffect.h"
@@ skipping 1028 matching lines @@
     } else {
         SkASSERT(dstSizePtr);
         srcRect = *srcRectPtr;
         dstSize = *dstSizePtr;
         if (srcRect.fLeft <= 0 && srcRect.fTop <= 0 &&
             srcRect.fRight >= bitmap.width() && srcRect.fBottom >= bitmap.height()) {
             flags = (SkCanvas::DrawBitmapRectFlags) (flags | SkCanvas::kBleed_DrawBitmapRectFlag);
         }
     }
 
-    if (paint.getMaskFilter()){
+    // if anti-aliasing without an msaa render target we must call drawRect
+    // or the result won't be anti-aliased
+    bool directDraw = fRenderTarget->isMultisampled() || !paint.isAntiAlias();
+    if (!directDraw) {
+        // if src and dst are pixel aligned we can still draw directly
+        if (fContext->getMatrix().rectStaysRect()) {
+            SkRect rect;
+            fContext->getMatrix().mapRect(&rect, srcRect);

[bsalomon, 2014/10/22 18:47:03]

Why does it matter if the src rect is aligned?

Also, this seems like it will break large bitmaps (> max texture size) that
currently get tiled. For those we need to apply AA just to the exterior edges of
the tiles.

There is a real problem here, that we don't antialias the edges of draw rect
calls. That definitely needs to be fixed but I think the tiling issue will
require a somewhat more complex solution.

+            const SkScalar *scalars = rect.asScalars();
+            bool isSrcPixelAligned = true;
+            for (int i = 0; i < 4; i++) {
+                if (!SkScalarIsInt(scalars[i])) {
+                    isSrcPixelAligned = false;
+                    break;
+                }
+            }
+
+            if (isSrcPixelAligned)
+                directDraw = SkScalarIsInt(dstSize.fWidth) &&
+                             SkScalarIsInt(dstSize.fHeight);
+        }
+    }
+
+    if (paint.getMaskFilter() || !directDraw) {
         // Convert the bitmap to a shader so that the rect can be drawn
-        // through drawRect, which supports mask filters.
+        // through drawRect, which supports mask filters and anti-aliasing
+        // without an msaa target.
         SkBitmap        tmp;    // subset of bitmap, if necessary
         const SkBitmap* bitmapPtr = &bitmap;
         SkMatrix localM;
         if (srcRectPtr) {
             localM.setTranslate(-srcRectPtr->fLeft, -srcRectPtr->fTop);
             localM.postScale(dstSize.fWidth / srcRectPtr->width(),
                              dstSize.fHeight / srcRectPtr->height());
             // In bleed mode we position and trim the bitmap based on the src rect which is
             // already accounted for in 'm' and 'srcRect'. In clamp mode we need to chop out
             // the desired portion of the bitmap and then update 'm' and 'srcRect' to
@@ skipping 762 matching lines @@
     GrLayerHoister::UnlockLayers(fContext, atlased, nonAtlased, recycled);
 
     return true;
 }
 
 SkImageFilter::Cache* SkGpuDevice::getImageFilterCache() {
     // We always return a transient cache, so it is freed after each
     // filter traversal.
     return SkImageFilter::Cache::Create(kDefaultImageFilterCacheSize);
 }