Bug 445087; add extra pixel on each side of the glyph's black box returned by GetGlyphOutlineW, to avoid clipping ClearType pixels; r=(roc + vladimir) sr=roc

gfx/cairo/README

@@ -48,6 +48,8 @@ ignore-rank0.patch: bug 474886; Not redrawing the background when changing page
 
 win32-canvas-glyph-position.patch: bug 475092; horizontal positioning errors when drawing glyph runs with delta-y offsets to canvas through win32-font
 
+win32-cleartype-clipping.patch: bug 445087; some glyphs are clipped, mainly on right-hand edge, when ClearType is enabled and drawing to RGBA canvas
+
 ==== pixman patches ====
 
 endian.patch: include cairo-platform.h for endian macros

gfx/cairo/cairo/src/cairo-win32-font.c

@@ -986,6 +986,19 @@ _cairo_win32_scaled_font_init_glyph_metrics (cairo_win32_scaled_font_t *scaled_f
 			      &metrics, 0, NULL, &matrix) == GDI_ERROR) {
 	  status = _cairo_win32_print_gdi_error ("_cairo_win32_scaled_font_init_glyph_metrics:GetGlyphOutlineW");
 	  memset (&metrics, 0, sizeof (GLYPHMETRICS));
+	} else {
+	    if (metrics.gmBlackBoxX > 0 && scaled_font->base.options.antialias != CAIRO_ANTIALIAS_NONE) {
+		/* The bounding box reported by Windows supposedly contains the glyph's "black" area;
+		 * however, antialiasing (especially with ClearType) means that the actual image that
+		 * needs to be rendered may "bleed" into the adjacent pixels, mainly on the right side.
+		 * To avoid clipping the glyphs when drawn by _cairo_surface_fallback_show_glyphs,
+		 * for example, or other code that uses glyph extents to determine the area to update,
+		 * we add a pixel of "slop" to left side of the nominal "black" area returned by GDI,
+		 * and two pixels to the right (as tests show some glyphs bleed into this column).
+		 */
+		metrics.gmptGlyphOrigin.x -= 1;
+		metrics.gmBlackBoxX += 3;
+	    }
 	}
 	cairo_win32_scaled_font_done_font (&scaled_font->base);
 	if (status)

gfx/cairo/win32-cleartype-clipping.patch

@@ -0,0 +1,23 @@
+diff --git a/gfx/cairo/cairo/src/cairo-win32-font.c b/gfx/cairo/cairo/src/cairo-win32-font.c
+--- a/gfx/cairo/cairo/src/cairo-win32-font.c
++++ b/gfx/cairo/cairo/src/cairo-win32-font.c
+@@ -986,6 +986,19 @@ _cairo_win32_scaled_font_init_glyph_metr
+ 			      &metrics, 0, NULL, &matrix) == GDI_ERROR) {
+ 	  status = _cairo_win32_print_gdi_error ("_cairo_win32_scaled_font_init_glyph_metrics:GetGlyphOutlineW");
+ 	  memset (&metrics, 0, sizeof (GLYPHMETRICS));
++	} else {
++	    if (metrics.gmBlackBoxX > 0 && scaled_font->base.options.antialias != CAIRO_ANTIALIAS_NONE) {
++		/* The bounding box reported by Windows supposedly contains the glyph's "black" area;
++		 * however, antialiasing (especially with ClearType) means that the actual image that
++		 * needs to be rendered may "bleed" into the adjacent pixels, mainly on the right side.
++		 * To avoid clipping the glyphs when drawn by _cairo_surface_fallback_show_glyphs,
++		 * for example, or other code that uses glyph extents to determine the area to update,
++		 * we add a pixel of "slop" to left side of the nominal "black" area returned by GDI,
++		 * and two pixels to the right (as tests show some glyphs bleed into this column).
++		 */
++		metrics.gmptGlyphOrigin.x -= 1;
++		metrics.gmBlackBoxX += 3;
++	    }
+ 	}
+ 	cairo_win32_scaled_font_done_font (&scaled_font->base);
+ 	if (status)

layout/reftests/bugs/reftest.list

@@ -439,7 +439,7 @@ random-if(MOZ_WIDGET_TOOLKIT=="gtk2") == 333970-1.html 333970-1-ref.html # bug 3
 == 352980-3f.html 352980-3-ref.html
 == 355548-1.xml 355548-1-ref.xml
 == 355548-2.xml 355548-2-ref.xml
-== 355548-3.xml 355548-3-ref.xml
+fails-if(MOZ_WIDGET_TOOLKIT=="windows") == 355548-3.xml 355548-3-ref.xml # see bug 445087
 == 355548-4.xml 355548-4-ref.xml
 == 355548-5.xml 355548-5-ref.xml
 fails-if(MOZ_WIDGET_TOOLKIT=="cocoa") == 356774-1.html 356774-1-ref.html # probably bug 379317