On Tue, 2010-03-02 at 10:35 -0500, Joseph Scheuhammer wrote: > Hi, > > Gnome-mag has a "cross-hair" feature for helping users find the mouse > cursor. An example graphic can be viewed here: > http://clown.atrc.utoronto.ca/aegis/GS-Mag/CrossHairs.png > > The issue is that the cross hairs cannot obscure what lies beneath > them. As you can see in the png, the colours of the cross hair are > blended with the background. > > Is colour blending possible within GnomeShell? My approach would be to > use clutter texture objects to form the cross hairs -- are there colour > blending functions for texture objects? I've looked at the online > documentation (http://www.clutter-project.org/docs/clutter/stable/), and > found transparency manipulations, but that's probably not enough. > Should I be diving into COGL? Looking somewhere else? > > Any advice would be appreciated.
To get this 'XOR' affect you'll need to go straight to OpenGL and use glLogicOp(). You can find examples of this with a web search. This will need to be done from C. Two approaches to code organization: - You could write a custom clutter actor that draws this way (Using cogl_begin_gl() and cogl_end_gl() around the OpenGL code) - You could paint the cross-hairs on top of the stage after the stage is completely painted, similar to how shell-recorder.c draws the recording icon and progress bar. (You still need the cogl_begin_gl() and cogl_end_gl() calls.) - Owen _______________________________________________ gnome-shell-list mailing list [email protected] http://mail.gnome.org/mailman/listinfo/gnome-shell-list
