Re: further notes on using Pango

From: Andrew Dunbar (hippietrail@yahoo.com)
Date: Fri Apr 26 2002 - 22:00:04 EDT

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     --- Tomas Frydrych <tomas@frydrych.uklinux.net>
    wrote: >
    > > But if each individual backend implements the same
    > API
    > > why is it more work?
    >
    > It does not. The Pango low-level API consists of two
    > parts. (1)
    > functions that are font backend independent (2)
    > functions that are
    > font backend specific. So to get a bitmap from a
    > string you call
    > pango_glyph_string(), it gives you the indices, and
    > you call
    > pango_ft2_render() with the glyph string, and get
    > the bitmap (the
    > names of the functions are probably different, just
    > shooting of the
    > top of my head.).
    >
    > That in itself is not the real problem; I have two
    > main reasons for
    > wanting to use the FT2 backend only at this stage.
    > (1) there are no
    > backends for Mac, QNX, BeOs and the win32 backend is
    > not, I
    > hear, very advanced yet; we would have to implement
    > these; I am
    > not prepared to do that, if someone else wants to,
    > is prepared to
    > learn about Pango internals and get to grips with
    > text handling on
    > platform XY, great. (2) If we use a variety of
    > backends, we will get
    > inconsistent behaviour across platforms; this is
    > really is quite a
    > serious problem, particularly on win32.
    >
    > Commiting to the FT2 back end at this stage does not
    > mean we
    > will be stuck with it. We will design the functions
    > for drawing the FT
    > bitmaps in the XP graphics class, but make them
    > virtual, so that if
    > someone wants to later implement different, platform
    > specific
    > versions, they will be able to just do so.

    Thanks for the description of the problem. I'm
    understanding it better and better. I don't agree
    with you about inconsistent behaviour though - we
    might get inconsistent rasterized glyphs but that's
    no problem. I'm personally interested in working on
    the Windows backend if needed, or any other OS that
    I am able to run. I do agree with you on how we
    should go about designing the functions etc and that's
    the important part.

    Andrew Dunbar.

    > Tomas

    =====
    http://linguaphile.sourceforge.net http://www.abisource.com

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