Re: Drawing charts with gtk

[Ronald Roth <rroth uiuc edu>]

These methods sound like they would work, and I think the color selection is a
good idea. OpenGL, however, is certainly overkill, since I this app would have
to run quickly even on computers which aren't OpenGL accelerated. I don't know
much about GnomeCanvas, I will research it. However, the drawings which this
will require will be very simple, just arcs of a disk, nothing more, so 
drawing area may be sufficient.

Thanks for your suggestions!


Carlos Pereira a dit ca:
> To select your directories, a very powerful method is:
>
> 1) Use a double-buffer;
>
> 2) When a press_event is received (meaning that
> the user wants to see the contents of a given 
> directory):
>
> i) read the x,y position where the user clicked;
> ii) draw each directory with a different color,
> in the background buffer; these colors have absolutely
> nothing to do with the colors that the user see on
> the foreground color. However, you must guarantee
> that the method used to draw the directories is
> exactly the same as in the normal drawing routines.
> iii) read the color of the x,y position in the
> background buffer;
> iv) the directory which has the color of the x,y position
> is the directory the user selected;
>
> Assuming that the user is using 8,8,8 bits for the r,g,b 
> channels, this method allow you to select among 65,535 
> directories in a single scan. If you need more ;-) you
> need to scan the background buffer again (so in practise
> there is really no limit for the number of objects to select).
>
> I don't know whether this is the best method in your case,
> it might be an overkill. You might also consider OpenGL (Mesa) to
> draw those fancy directories, though again it might be an overkill.
> This method to select objects is typically used in complex OpenGL 
> applications, where you have different classes of 3D objects, 
> 3D projections, lights, etc., so there is really no deterministic
> way to select objects.
>
> You should also consider GnomeCanvas, I believe is much better
> for these things than just a drawing_area.
>
> A raw drawing_area, without nothing on top (as GtkGLArea) is 
> intended only for very simple drawings. With OpenGL you could
> even use different textures to draw the background of each 
> directory... again this might an overkill (bloatware)...
>
> Carlos
>
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