[cairo] fractional positioning + glyph caching

[Behdad Esfahbod]

Hi Cosmin,

I was hoping to find time to look into these, but that seems unlikely to
happen soon.  Can you please file individual bugs in bugzilla for each of the
issues so we don't lose them?

Thanks,
behdad

On 13-06-27 08:40 AM, Cosmin Apreutesei wrote:
>>> A related question. I tried:
>>>
>>> cairo_set_antialias(CAIRO_ANTIALIAS_SUBPIXEL)
>>> font_options:set_antialias(CAIRO_ANTIALIAS_SUBPIXEL)
>>> cairo_set_font_options(font_options)
>>>
>>> but it does not affect cairo_show_glyphs(), which always renders in
>>> grayscale, but it does work with cairo_show_text() - a bug?
>>
>> Not expected.  Test case?
> 
> Actually, I rebuilt freetype with subpixel rendering support and now
> it works with cairo_show_glyphs() which renders glyphs with freetype's
> renderer it seems, while cairo_show_text() was rendering with winapi
> because it was using a windows font not a freetype-loaded font. It
> would be nice if these details would get a mention in the cairo doc
> (i.e. the fact that cairo uses font backend rasterizer instead of it's
> own rasterizer, like with cairo_glyph_path() and thus different
> rendering options are available and/or behave differently).
> 
> Anyway, I have an interactive demo that covers all combinations but
> it's windows only. Download the zip files from here
> https://code.google.com/p/lua-files/downloads/list and then run
> 
>> bin\luajit.exe harfbuzz_demo.lua
> 
>>> Also, I noticed that CAIRO_ANTIALIAS_BEST makes cairo_show_glyphs() to
>>> render each glyph horizontally stretched 3x - a bug?
>>
>> Wow.  Definitely.
> 
> To test this just set CAIRO_ANTIALIAS_BEST on any freetype-loaded font.
> 
> Here's a snippet:
> 
> FT_Library ft_lib = FT_New_Library()
> FT_Face ft_face = FT_New_Face(ft_lib, 'DejaVuSerif.ttf')
> cairo_font_face_t cairo_face = cairo_ft_font_face_create_for_ft_face(ft_face, 0)
> cairo_font_options_t font_options = cairo_font_options_create()
> cairo_font_options_set_antialias(font_options, CAIRO_ANTIALIAS_BEST)
> cairo_set_font_options(cr, font_options)
> cairo_set_source_rgb(cr, 1, 1, 1)
> cairo_set_font_face(cr, cairo_face)
> cairo_set_font_size(cr, 200)
> cairo_move_to(cr, 400, 300)
> cairo_show_text(cr, 'M')
> 

-- 
behdad
http://behdad.org/