Restore GDI text size rounding.
Add call to SkScalarRoundToScalar(). The old code calculated the scale
from the text size, but now the text size is calculated from the scale
(which is arguably the right way to think about it). However, the old
code always rounded the final resulting text size, while the new code
does not.
In the 'no hinting' case, the text size is already rounded to an integer
(so that the rest of the matrix is minimized). In the 'hinted' case, the
entire scale has been removed from the matrix, so the scale value is the
'real' residual size. The old code rounded this size, and the new code
should as well.
BUG=chromium:464784
Review URL: https://codereview.chromium.org/1014953002
Cherry-pick: 6f94076da504a9e292c7f6173b039d2692d47c51
Approval: https://code.google.com/p/chromium/issues/detail?id=464784#c25
diff --git a/src/ports/SkFontHost_win.cpp b/src/ports/SkFontHost_win.cpp
index 5ea55bd..311eb00 100755
--- a/src/ports/SkFontHost_win.cpp
+++ b/src/ports/SkFontHost_win.cpp
@@ -617,8 +617,8 @@
SetGraphicsMode(fDDC, GM_ADVANCED);
SetBkMode(fDDC, TRANSPARENT);
- // When GDI hinting, remove the entire Y scale to prevent 'subpixel' metrics.
- // When not hinting, remove only the gdiTextSize scale which will be applied by GDI.
+ // When GDI hinting, remove the entire Y scale from sA and GsA. (Prevents 'linear' metrics.)
+ // When not hinting, remove only the integer Y scale from sA and GsA. (Applied by GDI.)
SkScalerContextRec::PreMatrixScale scaleConstraints =
(fRec.getHinting() == SkPaint::kNo_Hinting || fRec.getHinting() == SkPaint::kSlight_Hinting)
? SkScalerContextRec::kVerticalInteger_PreMatrixScale
@@ -634,7 +634,19 @@
fGsA.eM21 = SkScalarToFIXED(-GsA.get(SkMatrix::kMSkewX));
fGsA.eM22 = SkScalarToFIXED(GsA.get(SkMatrix::kMScaleY));
- SkScalar gdiTextSize = scale.fY;
+ // When not hinting, scale was computed with kVerticalInteger, so is already an integer.
+ // The sA and GsA transforms will be used to create 'linear' metrics.
+
+ // When hinting, scale was computed with kVertical, stating that our port can handle
+ // non-integer scales. This is done so that sA and GsA are computed without any 'residual'
+ // scale in them, preventing 'linear' metrics. However, GDI cannot actually handle non-integer
+ // scales so we need to round in this case. This is fine, since all of the scale has been
+ // removed from sA and GsA, so GDI will be handling the scale completely.
+ SkScalar gdiTextSize = SkScalarRoundToScalar(scale.fY);
+
+ // GDI will not accept a size of zero, so round the range [0, 1] to 1.
+ // If the size was non-zero, the scale factors will also be non-zero and 1px tall text is drawn.
+ // If the size actually was zero, the scale factors will also be zero, so GDI will draw nothing.
if (gdiTextSize == 0) {
gdiTextSize = SK_Scalar1;
}
