[Fontconfig] Re: [Cairo] Text API proposal
otaylor at redhat.com
Tue Aug 12 08:32:41 EST 2003
On Mon, 2003-08-11 at 16:31, Keith Packard wrote:
> Around 14 o'clock on Aug 11, Owen Taylor wrote:
> > If you set up things to allow A), B) comes naturally. If you
> > have a CairoFontWin32 implementation of CairoFont, you can have
> > cairo_font_win32_from_logfont().
> One option is to always provide FreeType APIs (for portability) and then to
> add native APIs at some level to let people plug things in at this level.
> cairo_font_freetype_t cairo_font_freetype_create (FT_Font font);
> FT_Font cairo_font_freetype_ft_font (cairo_font_freetype_t cff);
> cairo_font_t cairo_font_from_freetype (cairo_font_freetype_t cff);
> cairo_font_win32_t cairo_font_win32_create (...);
> cairo_font_t cairo_font_from_win32 (cairo_font_win32_t cfw);
I don't think even linking to FreeType on, say, Windows is right; for
- One more dependency that won't be there normally
- Inconsistent rendering between different apps
- Having cairo_font_t be polymorphic on a single system is going
to be confusing and lead to problems where people assume that
a font *must* be a cairo_font_win32_t.
It isn't a bad idea to allow people to plug in a new font
system on the fly if they are doing something really custom, but
having two font systems always there is rather peculiar.
> then people could choose which they prefer. That leaves in question how to
> deal with fontconfig and the 'trivial' APIs. One option is to map
> fontconfig patterns to native fonts inside cairo so that (by default) you'd
> get native fonts on every platform:
This is an appealing choice, as long as the goals mentioned in my last
mail are possible: consistent list of fonts with the system, and minimal
overhead when not used.
> cairo_font_freetypet cairo_font_freetype_create_from_pattern (FcPattern *pattern)
> cairo_font_win32_t cairo_font_win32_create_from_pattern (FcPattern
> cairo_font_t cairo_font_create_from_pattern (FcPattern *pattern)
> Make cairo_font_create_from_pattern call one of the other two and return
> the casted result.
Pango uses a factory setup that would look like:
cairo_font_map_create_font_from_pattern (fontmap, pattern);
I think this works a bit better in general.
> Apps that "don't care" can use the generic functions, apps that "kind of
> care" can use just the freetype functions while apps that "really care"
> can have conditional code that selects the correct code depending on the
> underlying operating system.
Does this intermediate state of caring make sense? You shouldn't get one
rasterization if you "don't care" or "really care", and a different
rasterization if you "kind of care".
> What I want to avoid is attempting to provide an abstract interface on top
> of the underlying font system; that will just frustrate people and cause
> cairo to forever lag behind.
What do you mean by an "abstract interface"? Do you mean a generic
interface that goes beyond being useful for don't-care applications?
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