Re: How do I get X, Y pos and PangoLogAttr of each glyph in a rendered string?

[Alex Kerr <alex phonething com>]

Thank you again. Can I clarify four more small things please?

1. In the API ref for PangoLayoutLine, is GSList *runs a list of 
pointers to PangoLayoutRuns?

2. How do I get from the glyph positional info given in 
PangoGlyphGeometry to get a coordinate for the glyph on the Cairo 
drawing surface?

3. Is PangoGlyph a unique identifier for a specific glyph in a font - 
i.e. it's not shared with different glyphs, but if the same glyph is 
repeated it will have the same ID number?

4. If I'm iterating through the glyphs in a cluster using e.g. 
PangoGlpyhItemIter and the method show here: 
http://developer.gnome.org/pango/unstable/pango-Glyph-Storage.html#PangoGlyphItemIter 
how do I get to the data structures holding the glyph data and also 
cluster data from that - i.e. which function or pointer?

Thank you again for any clarification!

Alex

On 20/04/2011 16:05, Behdad Esfahbod wrote:
> On 04/20/11 09:14, Alex Kerr wrote:
> > Thanks very much for the help.
> >
> > > You definitely can do it with glyphs...
> > OK, cool, so how - i.e. which APIs and how do I tie them together please?
> > That's what's got me stuck!
> >
> > > ...but is that really what you want? There's simpler API in pango to do that
> > per cluster.
> >
> > I'm not sure :) What's the definition of a cluster (and for that matter a
> > glyph) ? I can't find this in the docs.
> A glyph is a single shape from the font.  A cluster is a mapping between one
> or more consecutive Unicode characters in the input text and one or more
> consecutive glyphs in the glyph array that collectively correspond to eachother.
>
>
> > And what's the simpler API you're referring to?
> The PangoLayoutIter API, which has next_cluster().
>
> If you want more direct access, check pango_layout_get_line(), and note that
> PangoLayoutRun is the same as PangoGlyphItem.  Then check PangoGlyphItemIter,
> or just do whatever you want to the glyph-item.
>
>
> > Thanks for the Python code. I can't actually use Python (don't program in it,
> > don't have it installed) but will read it as pseudocode and attempt similar in C!
> The code illustrates which API calls you can use.
>
> behdad
>
>
> > Cheers
> > Alex
> >
> >   On 20/04/2011 06:11, Behdad Esfahbod wrote:
> > > On 04/19/11 16:27, Alex Kerr wrote:
> > > > Hello,
> > > Hi Alex,
> > >
> > > > I'm using a really basic Cairo Pango prog as a test bed. It just displays a
> > > > short string on a Cairo surface using a Pango layout, which works fine.
> > > >
> > > > For each glyph in the string, I now want to get it's X,Y pos (and width and
> > > > height) on the rendered Cairo surface, and the PangoLogAttr data, e.g. so I
> > > > could draw a box around each glyph, or whatever.
> > > >
> > > > After a lot of reading the API stuff, and googling for examples, I'm not quite
> > > > sure how to tie the API functions together to achieve this. Anyone got any
> > > > suggestions, ideas, or code please?
> > > You definitely can do it with glyphs, but is that really what you want?
> > > There's simpler API in pango to do that per cluster.  Note that you cannot map
> > > a glyph to the original string (and hence PangoLogAttr).  You can only do that
> > > per cluster.
> > >
> > > Check PangoLayoutIter.
> > >
> > > I'm also attaching Python code that draws boxes around clusters.
> > >
> > > Hope that helps,
> > > behdad
> > >
> > > > Pseudocode for what I'm trying to do would be:
> > > >
> > > > 1. Render Pango text to Cairo surface (note: could be right-to-left, e.g.
> > > > Arabic, as well as left-to-right) - Done this.
> > > >
> > > > 2. For each glyph (or ligature) in the line of text:
> > > >       {
> > > >       3. Get X, Y, Width and Height of rendered glyph (or ligature)
> > > >       4. Get the PangoLogAttr structure for the same character
> > > >       5. Move onto the next glyph (/ligature/character) in the line
> > > >       }
> > > >
> > > > P.S. As a separate side note, I understand glyphs to be the separate
> > > > components of a final rendered character, i.e. the main body and diacritic (if
> > > > present) would be separate glyphs. Each glyph in turn could possibly be made
> > > > up of more than one UTF-8 character. The rendering engine can potentially
> > > > combine certain combinations of glyphs to form a single ligature. Glyphs or
> > > > ligatures can also be referred to as characters (so PangoLogAttr applies to
> > > > ligatures and glyphs?). Have I got this right!?
> > > >
> > > > Any help much appreciated :)
> > > >
> > > > Many thanks indeed!
> > > > Alex
> > > >
> > > >
> > > >
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