Re: problems understanding gtk3/gdk/cairo interaction

[Roger Davis <rbd soest hawaii edu>]

Hi John and Simon,

OK, experiment complete. Performance for me is very clearly not as good as 
Xlib-style XOR when drawing rubberband lines which span a screen-sized 
window (which is more or less typical for my apps, unfortunately), but on 
the other hand it's not unusable either, just somewhat annoyingly jerky. 
With smaller drawing areas (e.g., 300x300) the rubberbanding is perfectly 
smooth. Playing around with motion hint events might clean this up a 
little more. I'm basically doing a cairo_rectangle()/cairo_fill() from my 
entire off-screen surface to the GtkDrawingArea after every MotionNotify 
event. There are special cases, e.g., small rectangular rubberband boxes, 
where this is horrific overkill, but I also have cases where I need to 
rubberband larger collections of unpredictably-oriented line segments 
which span the full window, so I think my worst-case scenario experimental 
implementation has been a reasonable test. The outcome could have been 
worse, and I was expecting that it would be! For now I'll tell my users to 
wait 5 years and then buy new hardware. ;->

Thanks for all your suggestions!

Roger