Re: Another --> Re: GtkMovementStep of GtkTextView

[Havoc Pennington <hp redhat com>]

Chookij Vanatham <chookij thestork eng Sun COM> writes: 
> I'm just realizing that lam+alif case, the cursor can be in between.
> This is different than the hindi ligature which cursors couldn't be
> placed in the middle. If this isn't correct, anyone please clearify ?
> 
> Just want to make sure that I understand the point, in Pango technology,
> we are  trying to sepearate between the "display" algorithm and "cursor
> movement" algorithm. So, in this lam+alif case, the cursor can be moved/placed
> in between lam and alif but it's not because of 2 characters forms one cluster
> and they aren't one single grapheme. It shouldn't be matter because the
> display algorithm and cursor movement algorithm are seperate. Right ?
> 

There are two concepts:
 
 Cluster: a group of characters displayed as a single glyph. In Pango,  
          a cluster is simply a group of characters corresponding to 
          a glyph in PangoGlyphString

 Grapheme: a logical unit for editing; cursor can go between
           graphemes, deletion deletes a grapheme. Represented 
           by the is_cursor_position flag in PangoLogAttr.

For many languages, these are the same, but Pango is computing them
with totally different algorithms, and language engines can choose to
make them correspond or not as they see fit.

Havoc