win dw: Fallback to aliased if ClearType 'succeeds' but returns empty

src/ports/SkScalerContext_win_dw.cpp

Index: src/ports/SkScalerContext_win_dw.cpp
diff --git a/src/ports/SkScalerContext_win_dw.cpp b/src/ports/SkScalerContext_win_dw.cpp
index f27497be62ef7e40fdc88fede12c183624cbb227..a5771260bc0bafdece519288fc0571aef7d60b91 100644
--- a/src/ports/SkScalerContext_win_dw.cpp
+++ b/src/ports/SkScalerContext_win_dw.cpp
@@ -399,6 +399,7 @@ void SkScalerContext_DW::generateAdvance(SkGlyph* glyph) {
 }
 
 void SkScalerContext_DW::generateMetrics(SkGlyph* glyph) {

[Shrikant Kelkar, 2014/08/27 21:09:13]

nit: optional

generateMetricsInternal(SKGlyph* glyph, textureType, renderingMode) {
  move code from current generateMetrics() here
}
and call return generateMetricsInternal(glyph, fTextureType, fRenderingMode)
from generateMetrics()

+try_again:
     glyph->fWidth = 0;
 
     this->generateAdvance(glyph);
@@ -440,6 +441,12 @@ void SkScalerContext_DW::generateMetrics(SkGlyph* glyph) {
     RECT bbox;
     HRVM(glyphRunAnalysis->GetAlphaTextureBounds(fTextureType, &bbox),
          "Could not get texture bounds.");
+    if (bbox.right == 0 && bbox.left == 0 && bbox.top == 0 && bbox.bottom == 0 &&
+            fTextureType == DWRITE_TEXTURE_CLEARTYPE_3x1) {
+        fTextureType = DWRITE_TEXTURE_ALIASED_1x1;
+        fRenderingMode = DWRITE_RENDERING_MODE_ALIASED;
+        goto try_again;
+    }
 
     glyph->fWidth = SkToU16(bbox.right - bbox.left);
     glyph->fHeight = SkToU16(bbox.bottom - bbox.top);