Fix GrAtlasTextBlob bounds management

src/gpu/text/GrAtlasTextBlob.h

Index: src/gpu/text/GrAtlasTextBlob.h
diff --git a/src/gpu/text/GrAtlasTextBlob.h b/src/gpu/text/GrAtlasTextBlob.h
index 1c5ea5e60ea73d6e8253794e46813d4f922665c8..85dba63663ff0e25006359c2d7b6743cf70f8575 100644
--- a/src/gpu/text/GrAtlasTextBlob.h
+++ b/src/gpu/text/GrAtlasTextBlob.h
@@ -210,13 +210,11 @@ public:
     // We use this color vs the SkPaint color because it has the colorfilter applied.
     void initReusableBlob(GrColor color, const SkMatrix& viewMatrix, SkScalar x, SkScalar y) {
         fPaintColor = color;
-        fViewMatrix = viewMatrix;
-        fX = x;
-        fY = y;
+        this->setupViewMatrix(viewMatrix, x, y);
     }
 
-    void initThrowawayBlob(const SkMatrix& viewMatrix) {
-        fViewMatrix = viewMatrix;
+    void initThrowawayBlob(const SkMatrix& viewMatrix, SkScalar x, SkScalar y) {
+        this->setupViewMatrix(viewMatrix, x, y);
     }
 
     GrDrawBatch* test_createBatch(int glyphCount, int run, int subRun,
@@ -249,6 +247,16 @@ private:
                          SkDrawFilter* drawFilter, const SkMatrix& viewMatrix,
                          const SkIRect& clipBounds, SkScalar x, SkScalar y);
 
+    void setupViewMatrix(const SkMatrix& viewMatrix, SkScalar x, SkScalar y) {

[bsalomon, 2016/01/20 16:32:29]

what are x and y here?

[joshualitt, 2016/01/20 16:43:50]

I'm not 100% sure myself, but drawTextBlob(blob, x, y), for example.  They
become part of the masks.  I think its the offsets passed to the drawText call

[bsalomon, 2016/01/20 16:51:41]

I see, that makes sense. Add a comment?

+        fViewMatrix = viewMatrix;
+        if (!viewMatrix.invert(&fInitialViewMatrixInverse)) {
+            fInitialViewMatrixInverse = SkMatrix::I();

[bsalomon, 2016/01/20 16:32:29]

Is this really initial if we update it every time this is called? Seems like it
is always the inverse of fViewMatrix.

[joshualitt, 2016/01/20 16:43:50]

We only call setupViewMatrix when we fully regenerate the blob.  Otherwise, we
just update fViewMatrix and fX / fY directly.

[bsalomon, 2016/01/20 16:51:41]

Ok it'd be nice for that to be clearer. Maybe a comment?

+            SkDebugf("Could not invert viewmatrix\n");
+        }
+        fX = fInitialX = x;
+        fY = fInitialY = y;
+    }
+
     /*
      * Each Run inside of the blob can have its texture coordinates regenerated if required.
      * To determine if regeneration is necessary, fAtlasGeneration is used.  If there have been
@@ -276,7 +284,6 @@ private:
         Run()
             : fInitialized(false)
             , fDrawAsPaths(false) {
-            fVertexBounds.setLargestInverted();
             // To ensure we always have one subrun, we push back a fresh run here
             fSubRunInfo.push_back();
         }
@@ -290,10 +297,13 @@ private:
                 , fColor(GrColor_ILLEGAL)
                 , fMaskFormat(kA8_GrMaskFormat)
                 , fDrawAsDistanceFields(false)
-                , fUseLCDText(false) {}
+                , fUseLCDText(false) {
+                fVertexBounds.setLargestInverted();
+            }
             SubRunInfo(const SubRunInfo& that)
                 : fBulkUseToken(that.fBulkUseToken)
                 , fStrike(SkSafeRef(that.fStrike.get()))
+                , fVertexBounds(that.fVertexBounds)
                 , fAtlasGeneration(that.fAtlasGeneration)
                 , fVertexStartIndex(that.fVertexStartIndex)
                 , fVertexEndIndex(that.fVertexEndIndex)
@@ -338,6 +348,11 @@ private:
                 fVertexEndIndex = prev.vertexEndIndex();
             }
 
+            const SkRect& vertexBounds() const { return fVertexBounds; }
+            void joinGlyphBounds(const SkRect& glyphBounds) {
+                fVertexBounds.joinNonEmptyArg(glyphBounds);
+            }
+
             // df properties
             void setUseLCDText(bool useLCDText) { fUseLCDText = useLCDText; }
             bool hasUseLCDText() const { return fUseLCDText; }
@@ -347,6 +362,7 @@ private:
         private:
             GrBatchAtlas::BulkUseTokenUpdater fBulkUseToken;
             SkAutoTUnref<GrBatchTextStrike> fStrike;
+            SkRect fVertexBounds;
             uint64_t fAtlasGeneration;
             size_t fVertexStartIndex;
             size_t fVertexEndIndex;
@@ -368,7 +384,6 @@ private:
         }
         static const int kMinSubRuns = 1;
         SkAutoTUnref<SkTypeface> fTypeface;
-        SkRect fVertexBounds;
         SkSTArray<kMinSubRuns, SubRunInfo> fSubRunInfo;
         SkAutoDescriptor fDescriptor;
 
@@ -423,7 +438,10 @@ private:
     SkTArray<BigGlyph> fBigGlyphs;
     Key fKey;
     SkMatrix fViewMatrix;
+    SkMatrix fInitialViewMatrixInverse;
     GrColor fPaintColor;
+    SkScalar fInitialX;
+    SkScalar fInitialY;
     SkScalar fX;
     SkScalar fY;