[cairo] glyph extents

[Jonathan Kew]

On 18 Feb 2009, at 23:16, Jeff Muizelaar wrote:

> Does GetGlyphOutlineW return the proper extents if you change from
> GGO_METRICS to GGO_GRAY8_BITMAP?

No, that doesn't help. I still see the same clipped glyphs in my  
little Cairo test program, when cairo-surface-fallback.c uses these  
extents to clip its painting operation.

Very likely the extents it's returning would be correct for a  
"standard-smoothing" grayscale bitmap; the trouble is that ClearType  
wants to paint pixels that fall outside of that area, and they don't  
seem to offer us an API for getting *those* extents. So AFAICT there's  
no reasonable option except adding a "safety margin" to the results  
from GetGlyphOutlineW.

JK

> a la.
>
> diff --git a/src/cairo-win32-font.c b/src/cairo-win32-font.c
> index e9abfda..6c03c5f 100644
> --- a/src/cairo-win32-font.c
> +++ b/src/cairo-win32-font.c
> @@ -975,7 +975,7 @@ _cairo_win32_scaled_font_init_glyph_metrics  
> (cairo_win32_scaled_font_t *scaled_f
> 	    return status;
>
> 	if (GetGlyphOutlineW (hdc, _cairo_scaled_glyph_index (scaled_glyph),
> -			      GGO_METRICS | GGO_GLYPH_INDEX,
> +			      GGO_GRAY8_BITMAP | GGO_GLYPH_INDEX,
> 			      &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));
> @@ -1019,7 +1019,7 @@ _cairo_win32_scaled_font_init_glyph_metrics  
> (cairo_win32_scaled_font_t *scaled_f
> 	    return status;
>
> 	if (GetGlyphOutlineW (hdc, _cairo_scaled_glyph_index (scaled_glyph),
> -	                      GGO_METRICS | GGO_GLYPH_INDEX,
> +	                      GGO_GRAY8_BITMAP | GGO_GLYPH_INDEX,
> 			      &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));
>
> -Jeff