gecko/gfx/cairo/win32-cleartype-clipping.patch

24 lines
1.3 KiB
Diff

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)