Re: further notes on using Pango

From: Andrew Dunbar (hippietrail@yahoo.com)
Date: Thu Apr 25 2002 - 23:17:24 EDT

  • Next message: Andrew Dunbar: "Re: further notes on using Pango"

     --- Tomas Frydrych <tomas@frydrych.uklinux.net>
    wrote: >
    > Hi Leonard,
    >
    > > >(5) Develop a new XP font manager (some, but not
    > much platform
    > > >code needed), no complexities here, all we need
    > to is to be able to
    > > >retrieve font names and associate them with their
    > Pango descriptions
    > > >(not unlike the Unix font manager), probably from
    > a pregenerated text
    > > >file.
    > > Why doesn't FT fit the bill here - or is there
    > something that
    > > I am not understanding about what you mean by a
    > "Font
    > > Manager"?
    >
    > We need some internal mechanism for filling the font
    > combo box
    > with user readable names, and associating the font
    > names in the
    > combo box with a the descriptive data with the
    > PangoFont objects;
    > this should be straight forward. Pango itself takes
    > care of the 'real'
    > font management, it has a manager based on the xft
    > library that
    > maintains a database of fonts available through FT
    > and also has a
    > mechanism for automatic font substitution when the
    > requested font
    > is not available.

    This is something AbiWord would need control over.
    In general, it's a good thing but we don't want the
    user to get something other than exactly what she
    expects without us knowing ourselves right?
    Also, does it do this on a character basis or a font
    basis? MSWord, MSWordPad, and MSIE seem to map in
    characters from another font when single characters
    are missing from the requested font. This gets rid
    of the square boxes/question marks for missing
    characters but is not always what you want.

    > It seems we would not need to directly interact with
    > FreeType, the
    > Pango low-level api makes it possible to take a
    > string and get back
    > a finished FT_Bitmap, which is better than I first
    > thought, all we
    > would need is for each platform to implement a
    > function for drawing
    > this bitmap on screen, everything else can be XP. PS
    > output would
    > be a bit more complicated, but at the same time,
    > this would be an
    > excellent oportunity to move it into the XP land.

    Would it be possible to create a new Pango API
    analagous to the one that returns the FT_Bitmap to
    return PS. Don't we already have code that does most
    of this which could be migrated into Pango?

    > > >(6) replace the current shaping engine with
    > Pango.
    > > You tell us - that's your baby ;).
    > I do not see this as a major problem, this is one
    > thing that I am
    > prepared to do the necessary work on -- as long as
    > we can deal
    > with the portability issues, we are in business. I
    > have spent a better
    > part of the day examining the low level API of
    > Pango, and it does
    > seems to provide all we need, and I think the
    > changes would be
    > transparent to all our layout classes above
    > fp_TextRun (I can hear
    > Martin sighing with relief :-)).

    Woohoo (:

    > > >(7) get the existing Pango language modules other
    > than Hebrew
    > > >and Arabic to work with the FreeType back end. I
    > have no idea how
    > > >much work this would be, but without it we would
    > have only support
    > > >for Hebrew and Arabic, albeit much better than we
    > have now.
    > >
    > > Not a clue here. How many modules? What's
    > involved?
    >
    > For each language Pango handles there is a module,
    > at the
    > moment there are modules for Hebrew, Arabic, Hangul,
    > Indic, Tamil
    > and Thai, plus a basic module that handles
    > everything unhandled.
    > Unfortunately, but logically, each of these modules
    > requires a
    > separate implementation of interface with each
    > supported font
    > backend. At the moment, the only modules which have
    > the ft2
    > implementation are Hebrew and Arabic. I have no idea
    > how much
    > work it would be to add this to the other modules,
    > but suspect it
    > would require familiarity with Pango, FreeType and
    > the language in
    > question. (I only had a closer look at the Hebrew
    > module, and that
    > looks good, Dov Grobgeld done some work on proper
    > positioning of
    > vowels, accents, etc.).

    Those are all things I want to be familiar with (:

    Andrew Dunbar.

    > Tomas

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

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