Fix scaling issue with distance field text.

src/gpu/GrDistanceFieldTextContext.cpp

Index: src/gpu/GrDistanceFieldTextContext.cpp
diff --git a/src/gpu/GrDistanceFieldTextContext.cpp b/src/gpu/GrDistanceFieldTextContext.cpp
index 0aafc544d7831df982c28c21d0ccb4c8fd0c0ad9..c62978462af18ac7a1d452bcebaacd080e59d430 100755
--- a/src/gpu/GrDistanceFieldTextContext.cpp
+++ b/src/gpu/GrDistanceFieldTextContext.cpp
@@ -130,9 +130,9 @@ void GrDistanceFieldTextContext::setupCoverageEffect(const SkColor& filteredColo
     
     // set up any flags
     uint32_t flags = 0;
-    flags |= fContext->getMatrix().isSimilarity() ? kSimilarity_DistanceFieldEffectFlag : 0;
+    flags |= fTextMatrix.isSimilarity() ? kSimilarity_DistanceFieldEffectFlag : 0;
     flags |= fUseLCDText ? kUseLCD_DistanceFieldEffectFlag : 0;
-    flags |= fUseLCDText && fContext->getMatrix().rectStaysRect() ?
+    flags |= fUseLCDText && fTextMatrix.rectStaysRect() ?
     kRectToRect_DistanceFieldEffectFlag : 0;
     bool useBGR = SkDeviceProperties::Geometry::kBGR_Layout ==
     fDeviceProperties.fGeometry.getLayout();
@@ -179,7 +179,8 @@ void GrDistanceFieldTextContext::flushGlyphs() {
 
     GrDrawState* drawState = fDrawTarget->drawState();
     GrDrawState::AutoRestoreEffects are(drawState);
-    drawState->setFromPaint(fPaint, fContext->getMatrix(), fContext->getRenderTarget());
+
+    drawState->setFromPaint(fPaint, fTextMatrix, fContext->getRenderTarget());
 
     if (fCurrVertex > 0) {
         // setup our sampler state for our text texture/atlas
@@ -198,8 +199,8 @@ void GrDistanceFieldTextContext::flushGlyphs() {
         // Effects could be stored with one of the cache objects (atlas?)
         int coordsIdx = drawState->hasColorVertexAttribute() ? kGlyphCoordsWithColorAttributeIndex :
                                                                kGlyphCoordsNoColorAttributeIndex;
-        drawState->addCoverageEffect(fCachedEffect.get(), coordsIdx);
-        
+        drawState->setGeometryProcessor(fCachedEffect.get(), coordsIdx);
+
         // Set draw state
         if (fUseLCDText) {
             GrColor colorNoPreMul = skcolor_to_grcolor_nopremultiply(filteredColor);
@@ -448,18 +449,32 @@ inline void GrDistanceFieldTextContext::init(const GrPaint& paint, const SkPaint
 
     fStrike = NULL;
 
+    fTextMatrix = fContext->getMatrix();
+
+    // getMaxScale doesn't support perspective, so neither do we at the moment
+    SkASSERT(!fTextMatrix.hasPerspective());
+    SkScalar maxScale = fTextMatrix.getMaxScale();
+    SkScalar textSize = fSkPaint.getTextSize();
+    // if we have non-unity scale, we need to adjust our text size accordingly
+    // to avoid aliasing, and prescale the matrix by the inverse to end up with the same size
+    // TODO: do we need to do this if we're scaling down (i.e. maxScale < 1)?

[bsalomon, 2014/09/15 13:33:19]

Should your GM test this?

[jvanverth1, 2014/09/15 13:43:53]

Yes, probably :)

+    if (maxScale > 0 && !SkScalarNearlyEqual(maxScale, SK_Scalar1)) {
+        textSize *= maxScale;
+        fTextMatrix.preScale(SK_Scalar1 / maxScale, SK_Scalar1 / maxScale);
+    }
+
     fCurrVertex = 0;
 
     fVertices = NULL;
 
-    if (fSkPaint.getTextSize() <= kSmallDFFontLimit) {
-        fTextRatio = fSkPaint.getTextSize()/kSmallDFFontSize;
+    if (textSize <= kSmallDFFontLimit) {
+        fTextRatio = textSize / kSmallDFFontSize;
         fSkPaint.setTextSize(SkIntToScalar(kSmallDFFontSize));
-    } else if (fSkPaint.getTextSize() <= kMediumDFFontLimit) {
-        fTextRatio = fSkPaint.getTextSize()/kMediumDFFontSize;
+    } else if (textSize <= kMediumDFFontLimit) {
+        fTextRatio = textSize / kMediumDFFontSize;
         fSkPaint.setTextSize(SkIntToScalar(kMediumDFFontSize));
     } else {
-        fTextRatio = fSkPaint.getTextSize()/kLargeDFFontSize;
+        fTextRatio = textSize / kLargeDFFontSize;
         fSkPaint.setTextSize(SkIntToScalar(kLargeDFFontSize));
     }