Re: porting Xlib/Motif apps to GTK+

[Roger Davis <rbd soest hawaii edu>]

Hi Dov,

Thanks very much for that interesting code example. I built it and it 
seems to work fine, so there is apparently a solution to my problem, 
however complicated it may turn out to be. I assume since no one has given 
me a short 'yes' answer to my question of whether you can easily do an XOR 
line draw in Cairo that the answer is in fact 'no'. That's really too bad, 
XOR is such a nice, easy solution to quickly drawing a visible overlay 
line (when one is not particular about its actual color) and then rapidly 
restoring the original underlying drawing with an XOR erase. A few of my 
rubberbanding operations are unfortunately a lot more complicated than 
just a single line or box.

I will definitely save this very useful demo code, and probably bug you 
about it sometime in the future when I get to the point of rewriting all 
of my Xlib drawing ops. (Lucky you! ;-> )

Thanks again!

Roger

 On Wed, 29 Feb 2012, Dov Grobgeld wrote:

> On Wed, Feb 29, 2012 at 01:17, Roger Davis <rbd soest hawaii edu> wrote:
>       Â[stuff deleted]Â
>
>       Does Cairo have a way
>       of mimicking an X11 XOR-op GC for doing low-overhead ephemeral
>       drawing ops
>       of rubberband-lines, etc.?
>
> I have over the years been intrigued of how to do flicker free rubberband
> selection with gtk/cairo. My current solution may be seen here:
>
> https://github.com/dov/dovtk-lasso
>
> Feel free to poke me if you need more explanations and more documentation of
> how it works.
>
> Regards,
> Dov