Re: Copying bitmaps into bitmaps

[Edscott Wilson García <edscott imp mx>]

On Thu 17 Jan 2002 10:01, Havoc Pennington wrote:
> Edscott Wilson García <edscott imp mx> writes:
> > I've been trying to copy a bitmap into a bitmap with gdk_draw_pixmap(),
> > without success. Is it necesary to use XCopyPlane in lieu of some
> > gdk routine?
>
> When you say "without success," what happens? It should work fine.

I get messages like:

xftree: Fatal XLib internal error
BadMatch (invalid parameter attributes)
Request 62, Error 8

when I try to use the resulting bitmap. It croaks with only one copy from 
existing bitmap to a bitmap created with  
gdk_pixmap_new(window,pix_w,pix_h,1). 

After looking at a book by Barkakati, (X Window System Programming, 1991) he 
says that bitmaps should be copied into pixmaps by XCopyPlane(), not 
XCopyArea() (the latter being used by gdk_draw_pixmap()).

>
> > Basically all I want to do is a binary OR between the data in the 2
> > bitmaps.
>
> That isn't what gdk_draw_pixmap() normally does, it just copies the
> bits and overwrites the ones in dest. Look at gdk_gc_set_function(),
> I'm not sure it affects drawing a pixmap but I think it might.

Basically what I want is a transparency mask resulting from the combination 
of two (or more) pixmaps with different transparency masks. Which would be a 
binary AND between the data. I'll look at gdk_gc_set_function(), and see what 
I can do with it.

saludos,

Edscott

 
>
> Havoc