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

[Alex Kerr <alex phonething com>]

Just wondered if anyone can clarify these 4 points please or point me to 
the right doc?

Thanks very much,
Alex

On 21/04/2011 15:55, Alex Kerr wrote:
> 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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