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Fix subpixel metrics with GDI.

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The previous code uncovered a rather strange issue with GDI, where it
appears that alternating between two HFONTs with the same attributes but
vastly different heights does not appear to invalidate the the 'x'
metrics (the 'y' metrics appear to be correct). As a result it is
possible to get completely useless results from GetGlyphOutlineW. This
change works around the issue by simply scaling the one font to the
required sizes, which also saves us an HFONT.

Review URL: https://codereview.chromium.org/21047008

git-svn-id: http://skia.googlecode.com/svn/trunk@10425 2bbb7eff-a529-9590-31e7-b0007b416f81
This commit is contained in:
bungeman@google.com 2013-07-30 01:07:48 +00:00
parent a3aaf16e0f
commit 6a774a1f26
1 changed files with 17 additions and 19 deletions
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36
src/ports/SkFontHost_win.cpp
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@ -550,14 +550,17 @@ private:
* Used to find the magnitude of advances.
*/
MAT2 fGsA;
/** The total matrix without the textSize. */
MAT2 fMat22;
/** Scales font to EM size. */
MAT2 fHighResMat22;
HDC fDDC;
HFONT fSavefont;
HFONT fFont;
HFONT fHiResFont;
SCRIPT_CACHE fSC;
int fGlyphCount;
/** The total matrix which also removes EM scale. */
SkMatrix fHiResMatrix;
/** fG_inv is the inverse of the rotational part of the total matrix.
* Used to set the direction of advances.
@ -595,7 +598,6 @@ SkScalerContext_Windows::SkScalerContext_Windows(SkTypeface* rawTypeface,
, fDDC(0)
, fSavefont(0)
, fFont(0)
, fHiResFont(0)
, fSC(0)
, fGlyphCount(-1)
{
@ -735,16 +737,17 @@ SkScalerContext_Windows::SkScalerContext_Windows(SkTypeface* rawTypeface,
success = GetOutlineTextMetrics(fDDC, sizeof(otm), &otm);
}
if (0 != success) {
lf.lfHeight = -SkToS32(otm.otmEMSquare);
fHiResFont = CreateFontIndirect(&lf);
if (!fHiResFont) {
return;
}
SkScalar scale = SkIntToScalar(otm.otmEMSquare);
// construct a matrix to go from HIRES logical units to our device units
fRec.getSingleMatrix(&fHiResMatrix);
SkScalar scale = SkScalarInvert(SkIntToScalar(otm.otmEMSquare));
fHiResMatrix.preScale(scale, scale);
SkScalar textScale = scale / textSize;
fHighResMat22.eM11 = float2FIXED(textScale);
fHighResMat22.eM12 = float2FIXED(0);
fHighResMat22.eM21 = float2FIXED(0);
fHighResMat22.eM22 = float2FIXED(textScale);
SkScalar invScale = SkScalarInvert(scale);
fHiResMatrix = A;
fHiResMatrix.preScale(invScale, invScale);
}
}
@ -778,9 +781,6 @@ SkScalerContext_Windows::~SkScalerContext_Windows() {
if (fFont) {
::DeleteObject(fFont);
}
if (fHiResFont) {
::DeleteObject(fHiResFont);
}
if (fSC) {
::ScriptFreeCache(&fSC);
}
@ -827,7 +827,6 @@ void SkScalerContext_Windows::generateAdvance(SkGlyph* glyph) {
this->generateMetrics(glyph);
}
static const MAT2 gMat2Identity = {{0, 1}, {0, 0}, {0, 0}, {0, 1}};
void SkScalerContext_Windows::generateMetrics(SkGlyph* glyph) {
SkASSERT(fDDC);
@ -898,17 +897,15 @@ void SkScalerContext_Windows::generateMetrics(SkGlyph* glyph) {
glyph->fRsbDelta = 0;
glyph->fLsbDelta = 0;
if (fHiResFont) {
SelectObject(fDDC, fHiResFont);
if (this->isSubpixel()) {
sk_bzero(&gm, sizeof(gm));
status = GetGlyphOutlineW(fDDC, glyphId, GGO_METRICS | GGO_GLYPH_INDEX, &gm, 0, NULL, &gMat2Identity);
status = GetGlyphOutlineW(fDDC, glyphId, GGO_METRICS | GGO_GLYPH_INDEX, &gm, 0, NULL, &fHighResMat22);
if (GDI_ERROR != status) {
SkPoint advance;
fHiResMatrix.mapXY(SkIntToScalar(gm.gmCellIncX), SkIntToScalar(gm.gmCellIncY), &advance);
glyph->fAdvanceX = SkScalarToFixed(advance.fX);
glyph->fAdvanceY = SkScalarToFixed(advance.fY);
}
SelectObject(fDDC, fFont);
} else if (!isAxisAligned(this->fRec)) {
status = GetGlyphOutlineW(fDDC, glyphId, GGO_METRICS | GGO_GLYPH_INDEX, &gm, 0, NULL, &fGsA);
if (GDI_ERROR != status) {
@ -920,6 +917,7 @@ void SkScalerContext_Windows::generateMetrics(SkGlyph* glyph) {
}
}
static const MAT2 gMat2Identity = {{0, 1}, {0, 0}, {0, 0}, {0, 1}};
void SkScalerContext_Windows::generateFontMetrics(SkPaint::FontMetrics* mx, SkPaint::FontMetrics* my) {
if (!(mx || my)) {
return;