[Fedora-trans-ar] Re: Arabic issue #34: Mouse and keyboard selection is a little buggy with LAM-ALEF in a QTextEdit/QLineEdit

[Munzir Taha]

On Saturday 26 March 2005 17:34, Munzir Taha wrote:
> Hi,
> Qt version: 4.0.0-b2-snapshot-20050315
> 2.6.10-1mdk i686 AMD Athlon(tm) 64 Processor 3200+ GNU/Linux
>
> If I typed ARABIC LETTER LAM (U+0644) followed by ARABIC LETTER ALEF
> (U+0627) in a QTextEdit or QLineEdit, I can't select either of the two
> letters using the keyboard or the mouse in a proper way.

If it's not yet clear, here is a more detailed explanation addressing the 
basic Arabic ligatures which are composed of the letter Lam followed 
logically by the letter Alef (or variants of Alef like Alef with Hamza above 
or Alef with Madda above). 

When a Lam is followed by an Alef, the two characters must be processed 
logically like two characters, although they are visualized with one glyph. 

If the current position is before the Lam and the user presses Delete, the Lam 
will be deleted and the Lamalef glyph will be replaced by an Alef glyph. 
If the current position is after the Alef and the user presses Backspace, the 
Alef will be deleted and the Lamalef glyph will be replaced by a Lam glyph. 

Visually, the Lamalef glyph must be processed like two glyphs with no space 
between. The cursor may appear before the Lamalef, after the Lamalef, or in 
the middle of the Lamalef. When the cursor appears in the middle of the 
Lamalef, the current position in the logical buffer is between Lam and Alef. 

If the cursor is before the Lamalef and the user presses left arrow, the 
cursor will appear in the middle of the Lamalef. If the user presses left 
arrow again, the cursor will appear after the Lamalef. 
If the cursor is after the Lamalef and the user presses right arrow, the 
cursor will appear in the middle of the Lamalef. If the user presses right 
arrow again, the cursor will appear before the Lamalef. 
It is possible to position the cursor in the middle of a Lamalef using the 
mouse, or up/down arrows, or PageUp/PageDown. 
It is possible to select only the right part or only the left part of the 
Lamalef glyph, either using arrow keys or the mouse. The right part 
corresponds to selection of the Lam; the left part corresponds to selection 
of the Alef. 

Note: a good implementation of these requirements for Arabic ligatures can be 
seen in Notepad under Arabic Windows NT4, or Windows 2000. It is good to know 
that when the keyboard language is Arabic, the "G" key generates a Lam, the 
"H" key generates an Alef, and the "B" key generates Lam followed by Alef.

Hope this is more clear now.

-- 
Munzir Taha  PGP Key available
gpg --recv-keys --keyserver www.mandrakesecure.net F0671821

Telecommunications and Electronics Engineer
Mandrake Club Member
Maintainer of the OpenBugs project page at
http://www.arabic-fedora.org/munzir/OpenBugs.html
Maintainer of Fedora Arabic Translation Project
https://listman.redhat.com/mailman/listinfo/fedora-trans-ar
CIW Designer, ICDL, MOUS, Linux+, LPI 101
New Horizons CLC, Riyadh, SA