Use bitmap-based glyph metrics instead of outline-based metrics

src/ports/SkFontHost_win.cpp

 
 /*
  * Copyright 2006 The Android Open Source Project
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 #include "SkAdvancedTypefaceMetrics.h"
 #include "SkBase64.h"
@@ skipping 795 matching lines @@
         apply_outset(glyph, fOutset);
         return;
     }
 
     GLYPHMETRICS gm;
     sk_bzero(&gm, sizeof(gm));
 
     glyph->fRsbDelta = 0;
     glyph->fLsbDelta = 0;
 
-    // Note: need to use GGO_GRAY8_BITMAP instead of GGO_METRICS because GGO_METRICS returns a smaller
-    // BlackBlox; we need the bigger one in case we need the image.  fAdvance is the same.
-    uint32_t ret = GetGlyphOutlineW(fDDC, glyph->getGlyphID(0), GGO_GRAY8_BITMAP | GGO_GLYPH_INDEX, &gm, 0, NULL, &fMat22);
+    // Note 1: Don't use GGO_GRAY8_BITMAP because it always returns outline-based metrics.
+    //         When embedded bitmap exists, bitmap-based metrics have to be used.
+    //         If not, slightly smaller metrics is returned (anti-alias gap)
+    //         so outset is necessary.
+    // Note 2: Don't change glyph shape because in that case GetGlyphOutline always returns
+    //         outline-based metrics.
+    fMat22.eM12 = SkFixedToFIXED(-SkFIXEDToFixed(fMat22.eM12));
+    fMat22.eM22 = SkFixedToFIXED(-SkFIXEDToFixed(fMat22.eM22));
+    uint32_t ret = GetGlyphOutlineW(fDDC, glyph->getGlyphID(0), GGO_GLYPH_INDEX, &gm, 0, NULL, &fMat22);
     if (GDI_ERROR == ret) {
         ensure_typeface_accessible(fRec.fFontID);
-        ret = GetGlyphOutlineW(fDDC, glyph->getGlyphID(0), GGO_GRAY8_BITMAP | GGO_GLYPH_INDEX, &gm, 0, NULL, &fMat22);
+        ret = GetGlyphOutlineW(fDDC, glyph->getGlyphID(0), GGO_GLYPH_INDEX, &gm, 0, NULL, &fMat22);
     }
+    fMat22.eM12 = SkFixedToFIXED(-SkFIXEDToFixed(fMat22.eM12));
+    fMat22.eM22 = SkFixedToFIXED(-SkFIXEDToFixed(fMat22.eM22));
 
     if (GDI_ERROR != ret) {
         if (ret == 0) {
             // for white space, ret is zero and gmBlackBoxX, gmBlackBoxY are 1 incorrectly!
             gm.gmBlackBoxX = gm.gmBlackBoxY = 0;
         }
         glyph->fWidth   = gm.gmBlackBoxX;
         glyph->fHeight  = gm.gmBlackBoxY;
-        glyph->fTop     = SkToS16(gm.gmptGlyphOrigin.y - gm.gmBlackBoxY);
+        glyph->fTop     = SkToS16(-gm.gmptGlyphOrigin.y);
         glyph->fLeft    = SkToS16(gm.gmptGlyphOrigin.x);
         glyph->fAdvanceX = SkIntToFixed(gm.gmCellIncX);
         glyph->fAdvanceY = -SkIntToFixed(gm.gmCellIncY);
 
         // we outset in all dimensions, since the image may bleed outside
         // of the computed bounds returned by GetGlyphOutline.
-        // This was deduced by trial and error for small text (e.g. 8pt), so there
-        // maybe a more precise way to make this adjustment...
-        //
-        // This test shows us clipping the tops of some of the CJK fonts unless we
-        // increase the top of the box by 2, hence the height by 4. This seems to
-        // correspond to an embedded bitmap font, but not sure.
-        //     LayoutTests/fast/text/backslash-to-yen-sign-euc.html
-        //
+        // it is because we ignore grayscale or ClearType anti-alias
+        // in getting metrics.
+        // Note: GetGlyphOutline doesn't support ClearType.
         if (glyph->fWidth) {    // don't outset an empty glyph
             glyph->fWidth += 4;
             glyph->fHeight += 4;
             glyph->fTop -= 2;
             glyph->fLeft -= 2;
 
             apply_outset(glyph, fOutset);
         }
 
         if (fHiResFont) {
@@ skipping 902 matching lines @@
         rec->fMaskFormat = SkMask::kA8_Format;
     }
 #endif
 
     LogFontTypeface* logfontTypeface = static_cast<LogFontTypeface*>(typeface);
     if (!logfontTypeface->fCanBeLCD && isLCD(*rec)) {
         rec->fMaskFormat = SkMask::kA8_Format;
         rec->fFlags &= ~SkScalerContext::kGenA8FromLCD_Flag;
     }
 }