From 35307fc66f649cc042ec07b7b79277d7ee5987f3 Mon Sep 17 00:00:00 2001 From: Jonathan Kew Date: Tue, 11 May 2010 15:12:01 -0400 Subject: [PATCH] win32: Grow glyph extents to account for ClearType Add extra pixel on each side of the glyph's black box returned by GetGlyphOutlineW, to avoid clipping ClearType pixels. From https://bugzilla.mozilla.org/show_bug.cgi?id=445087 --- src/cairo-win32-font.c | 13 +++++++++++++ 1 file changed, 13 insertions(+) diff --git a/src/cairo-win32-font.c b/src/cairo-win32-font.c index 596ca2597..cb253dd27 100644 --- a/src/cairo-win32-font.c +++ b/src/cairo-win32-font.c @@ -979,6 +979,19 @@ _cairo_win32_scaled_font_init_glyph_metrics (cairo_win32_scaled_font_t *scaled_f GGO_METRICS | GGO_GLYPH_INDEX, &metrics, 0, NULL, &matrix) == GDI_ERROR) { 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);