XOR drawing in Cocoa

[Dan.Crevier at pobox.com (Dan Crevier)]

On 3/3/2002 11:10 AM, "Joe Esch" <joe@xxxxxxxxxxxx> wrote:

> I can draw the temporary graphics in OpenGL, but I don't know how to update
> them without redrawing the entire scene.  For a large model, this can be
> farily slow.
> 
> What I am looking for is a way to display some temporary graphics (e.g. a
> selection rectangle) over the OpenGL view without having to redraw the
> entire OpenGL scene on every mouse move.
> 
> I am already using the stencil buffer for computing shadows.

One solution is to use an overlay window.  This is what the Finder does.
You basically create a window with some low % opacity that is drawn over
your content.

Dan