Fix scaling issue with distance field text.

src/gpu/GrDistanceFieldTextContext.cpp

 /*
  * Copyright 2013 Google Inc.
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 #include "GrDistanceFieldTextContext.h"
 #include "GrAtlas.h"
 #include "SkColorFilter.h"
@@ skipping 109 matching lines @@
 }
 
 void GrDistanceFieldTextContext::setupCoverageEffect(const SkColor& filteredColor) {
     GrTextureParams params(SkShader::kRepeat_TileMode, GrTextureParams::kBilerp_FilterMode);
     GrTextureParams gammaParams(SkShader::kClamp_TileMode, GrTextureParams::kNone_FilterMode);
     
     uint32_t textureUniqueID = fCurrTexture->getUniqueID();
     
     // 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();
     flags |= fUseLCDText && useBGR ? kBGR_DistanceFieldEffectFlag : 0;
     
     // see if we need to create a new effect
     if (textureUniqueID != fEffectTextureUniqueID ||
         filteredColor != fEffectColor ||
         flags != fEffectFlags) {
         if (fUseLCDText) {
@@ skipping 26 matching lines @@
     
 }
 
 void GrDistanceFieldTextContext::flushGlyphs() {
     if (NULL == fDrawTarget) {
         return;
     }
 
     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
         SkASSERT(SkIsAlign4(fCurrVertex));
 
         // get our current color
         SkColor filteredColor;
         SkColorFilter* colorFilter = fSkPaint.getColorFilter();
         if (colorFilter) {
             filteredColor = colorFilter->filterColor(fSkPaint.getColor());
@@ skipping 246 matching lines @@
     }
 
     fCurrVertex += 4;
 }
 
 inline void GrDistanceFieldTextContext::init(const GrPaint& paint, const SkPaint& skPaint) {
     GrTextContext::init(paint, 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)?
+    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));
     }
 
     fUseLCDText = fSkPaint.isLCDRenderText();
 
     fSkPaint.setLCDRenderText(false);
     fSkPaint.setAutohinted(false);
     fSkPaint.setHinting(SkPaint::kNormal_Hinting);
     fSkPaint.setSubpixelText(true);
 
@@ skipping 179 matching lines @@
                                       SkScalarToFixed(x) - (glyph.fAdvanceX >> alignShift),
                                       SkScalarToFixed(y) - (glyph.fAdvanceY >> alignShift),
                                       fontScaler);
             }
             pos += scalarsPerPosition;
         }
     }
 
     this->finish();
 }