Re: [Freetype] glyph caching

[Leonard Rosenthol]

At 12:58 PM +0200 11/22/00, George Petrov Georgiev wrote:
> freetype is too slow for direct rendering of each char in the text,
> without any chaching.

	True, but it's not just FreeType - it's ANY 
vector/outline-based type engine.  (you don't really think that Mac 
OS and Windows (for example) don't do caching, do you??)


> I can spend 10~15Mb for  glyph->bitmap cache for gaining 20-30 times faster
> text layouting. Is this a dream? I think that itsn't :).

	Nope, caching the bitmaps (and even the font information) is 
the right approach to the problem.  I do this two applications of 
mine that use FreeType, and it noticeably improves performance - 
though I don't know if it's 20-30x.  It's really going to depend on 
the text in question.   Rendering lots of the same character in the 
same font/face will certainly improve, but text in lots of 
fonts/faces with different characters won't (since it's still going 
to have to raster them at least once).

	If you are looking for a glyph cache implementation, check 
out rsvg-ft.c, which is part of librsvg which is part of nautilus 
which is part of GNOME. 
(<http://cvs.gnome.org/registry/file.cgi?cvsroot=/cvs/gnome&file=rsvg-ft.c&dir=nautilus/librsvg>)


> Don't ask me why I
> don't  render all needed fonts and sizes in advance, if and I want to have a
> so fast engine :).

	I don't believe that this will actually speed things up any 
more than a "cache as you go" scheme (and might actually make total 
processing slower) since the delay is the first rasterization not 
secondary ones, and a "cache as you go" would only rasterizer USED 
glyphs, rather than every glyph (which can be expensive time wise).


Leonard
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Leonard Rosenthol                       <mailto:address@hidden>
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