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Duplicate Windows in Mac OS X

2010-04-15

Allow me to introduce a project I’ve had lying around for some months that I’ve found extremely useful thus far: Duplicate Windows. It allows you to create a visual copy of any window on Mac OS X, and keep the new window updated on-the-fly.

The program came about when I was teaching a statistics lab twice a week in Fall 2009. The first portion of every lab, I performed various sorts of demonstrations using the statistical software, R. As is usual in such cases, I stood up front facing the class, with the projection screen behind me. The perfect scenario to mirror the display on my laptop and the projector.

But then, I wanted to have some personal notes in-front of me to present the material in the way I had carefully prepared, and I also wanted to have a small bank of pre-typed commands to copy and paste into the R console to speed up the lecture portion of the lab. I didn’t want these resources projected in-front of the entire class… the perfect scenario to set my laptop in extended desktop mode.

One morning, I decided I needed the best of both worlds. I wrote a dead-simple program that continuously takes a screenshot of a window you select, and renders it onto another window, thereby visually duplicating the original window. So now I can have the R console open on my laptop, with my notes beside it, and just duplicate the R window onto the projector, with the displays set to extended desktop mode.

Duplicate Windows has proven useful in a variety of other circumstances, but still stands in my mind as an excellent presentation tool to have at your disposal. If you’ve ever wished you could “mirror” only a single window, now you can (as long as you’re running Mac OS X, Snow Leopard). See a video of the software in action.