On 4 April 2012 15:37, Tilton, James C. (GSFC-6063) <james.c.til...@nasa.gov> wrote: > Your response is very helpful. The one key question that remains for me is: > > How do I draw a "floating crosshair"?
You need to do it by hand, unfortunately, though it's not so hard (I think). The trick (in my opinion) is to have a compositing model for your drawing areas. Imagine them as a stack of 2D elements which you draw back-to-front in your expose handler. I wrote a mail on this a month or so ago, though it was in relation to rubber-banding: -------- The implementation can be very simple, you don't need to really keep separate layers around. You could just have a bool in your draw state for "display rubberband" and that would be enough. Your expose might looks like: expose: draw background if rubber-band: draw rubberband then in your mouse event handler you could have: on left-down: set rubber-band queue draw for pixels touched by rubber band on motion: if rubber-band: queue draw for pixels touched by rubber band update band position queue draw for pixels touched by rubber band on left-up: unset rubber-band queue draw for pixels touched by rubber band The various canvas widgets do basically exactly this for you. J _______________________________________________ gtk-app-devel-list mailing list gtk-app-devel-list@gnome.org http://mail.gnome.org/mailman/listinfo/gtk-app-devel-list
