Q. How can I check on the progress of the tracer module?

A. If you are using the tracer module in conjunction with display tracker, and it's taking a while to compute and you want to see how far along the tracing is going, cause the display tracker window to get an expose event (iconify it, un-iconify it or hide it and re-show it). Because the output from tracer is in shared memory, all of the currently rendered portion is overwriting the existing buffer. You can use this technique for tracking the progress of the module.

This trick does not work if (a) it's the first time through, (b) you've just changed the output image size from tracer, (c) the modules are on different machines, or (d) you use display image or the Image Viewer modules.