[cairo] cairo_select_font() (was: cairo_scale_font/cairo_transform_font())

[Ned Konz]

On Saturday 19 March 2005 10:45 am, Øyvind Kolås wrote:
> Ok, this would make it possible to act upon the current font object
> from a binding. I'd also like to split out the components of the
> "FontName", making a coding style like:
>
> cr.font.name = "Sans"
> cr.font.slant = Cairo::FONT_SLANT_ITALIC
> cr.font.size = 12
>
> possible in for instance the ruby binding.

I don't think so, since what Owen is calling the font_name_t has not 
necessarily got the (human-centric) name of the font in it.

Instead, this is a structure defined by a given backend.

cairo_scaled_font_t (*create_scaled_font) (void *name, cairo_matrix_t 
*font_matrix, cairo_matrix_t *ctm);

And the "name" is not necessarily what most of us think of as a font name (it 
would probably be a filename in the case of the FT2 backend). It's just some 
identifier that can be used to find the description of an unscaled font.

Since different backends would define "name" differently, you wouldn't have a 
single way of getting (say) a font family name from an abstract font_name_t.

Instead what you'd want to do for a language binding is to keep track of the 
constructor arguments, and/or know how to query the different back-end 
specific font_name_t objects:

class CairoFontName < Object
end

class CairoFtFontName < CairoFontName
 def initialize(ftFace, loadFlags)
  @face = ftFace
  @flags = loadFlags
 end

 def self.newFromFile(filename, loadFlags=0)
  face = FT2Face.new(filename)
  self.new(face, loadFlags)
 end

 def self.newFromFcPattern(fcPattern)
  face, flags = findFtFace(fcPattern)
  self new(face, flags)
 end

 def familyName
  @face.familyName
 end
end

class CairoSimpleFontName < CairoFontName
 def initialize(familyName, slant=SlantRoman, weight=WeightRegular)
  @familyName = familyName
  @slant = slant
  @weight = weight
 end

 def familyName
  @familyName
 end
end

class CairoContext
 # takes a CairoFontName
 def setFontName(fname)
  ...
 end
end

-- 
Ned Konz
http://bike-nomad.com/squeak/