RE: Question about the GdkGC

["Tom Liu" <tom liu flextrade com>]

Ok I understand why create GdkGC and use GdkGC both need the GdkDrawable
parameter because one created GC can apply to multiple window.

But how about the performance?
I saw a program need to draw 10 color on a drawable. They just create 10
GC! And they nevery release these GC.
It this right way to do so? Should I create one GC and change the colors
when need it?

I am a windows programmer, usually when I need to draw something in the
window, I just get a gc, change color, draw, change color back, release
gc.

Looks gtk work like this. 
        Create multiple GC, use these when needed over and over again.




-----Original Message-----
From: gtk-app-devel-list-admin gnome org
[mailto:gtk-app-devel-list-admin gnome org] On Behalf Of Tristan Van
Berkom
Sent: Wednesday, November 12, 2003 11:56 AM
To: Tom Liu
Cc: gtk-app-devel-list gnome org
Subject: Re: Question about the GdkGC

Tom Liu wrote:

> When I create a GdkGC, I have to give a GdkDrawable to attach this GC,
> But when I draw line or rectangle, I still need the GdkDrawable as
> parameter.
You need to provide a GdkDrawable so that the GdkGC can reference a
colormap; the colormap is created when you create a GdkDrawable
and; if I'm not mistaken; thats because creating the colormap requires
some knowlage of the rendering architechture (Win or XFree86)
(and thats handled at the GdkDrawable level).

> Is these because one GdkGC can work on multile GdkDrawable after it
> created?
>  
Yes it can.

> Another question: the CreateGC and releaseGC is a expensive job? Should
> I create and release it every time I need to draw or just keep a global
> copy for better performance.
>  
A GdkGC is like a structure that holds a bunch of paramaters
to draw with when using any GdkDrawables; instead of passing
alot of arguments to the drawing functions; the arguments that
probably won't change from one function call to the next; are
stored in the graphics context.

Does that help ?

Regards,
                                                -Tristan

-- 
"Life would be so much easier if we could just look at the source code."
        -- Francois Baumier



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