Qt-based graphics backend - idea.

[Maciek Gajewski]

Hello again.

Few days ago I've announced my plans for creating Qt-based plotter.
I've been told about new graphics code in latest octave sources. So I changed 
my approach and decided to follow this path, instead of creating standalone 
plotter.

My current plan is to create Qt-based graphics backend.

Design:
1. create new backend (inherit base_graphics_backend), registered in 
some 'init' function.
2. during initialization - create new thread for GUI operation, intitialize Qt 
facilities in this thread.
3. In response for backend calls (close_figure, redraw_figure, print), send 
appropriate message to GUI thread, also copy object properties (syncing 
threads), so they can be safely accessed by GUI code from GUI thread.
4. Draw everything in GUI thread, using data from copied property tree.
5. All callback calls triggered by GUI (i.e. ButtonDownFcn) in GUI thread 
should be queued, and called from main thread in function registered 
with 'input_event_hook'.

(step 1, 2 and partially 3 are somehow implemented already)

I'd like to ask You for opinion and ideas - is anyone seeing any major flaw in 
above design?

Also, I'd like to ask about current status of 'uicontrol' implementation. Is 
there any planed? My entire project comes from need of having decent 2D 
plotting, especially using 'image', and basic uicontrols. So if no one is 
working on uicontrols, I'd like to add at least basic ones. I need pointers 
on when to start.

Thanks in advance

Maciek Gajewski