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

src/gpu/SkGpuDevice.cpp

Index: src/gpu/SkGpuDevice.cpp
diff --git a/src/gpu/SkGpuDevice.cpp b/src/gpu/SkGpuDevice.cpp
index 83cdef701a077f71614feb6f202a327d75fdb810..0a678c69591b2476de1508142f3b1cab51eead77 100644
--- a/src/gpu/SkGpuDevice.cpp
+++ b/src/gpu/SkGpuDevice.cpp
@@ -1046,9 +1046,33 @@ void SkGpuDevice::drawBitmapCommon(const SkDraw& draw,
         }
     }
 
-    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;