One of the UI concessions OS X Lion makes to a time-honored Microsoft Windows feature, is the addition window-resizing hotspots on all edges of a given window. Traditionally, Mac users have been limited to resizing windows only through the use of the “Zoom” button in the title bar, or by clicking and dragging the resize control at the bottom-right corner of a window.

Now you can grab any edge of a window and grow or shrink it to suit your wants. What I didn’t notice until today, however, are a few interesting variations on window resizing that are facilitated by pressing a modifier key while resizing.

Hold the option key while resizing to cause changes in the window’s width or height to be made in equal measure on each side of the window. For example, clicking and dragging the right edge of a window with option depressed will cause the left side to grow or shrink in mirrored fashion. For lack of a better term, I’ll call this balanced resizing.

Hold the shift key while resizing to impose constrained resizing. Whatever direction you grow or shrink the window, adjustments will be made so that the ratio of height to width remains the same.

These are some pretty geeky resizing modes. I don’t foresee using them particularly often, but it’s interesting to know they are there.

(I did some preliminary Googling before sharing this, and didn’t see any documentation come up. I’ve since noticed that Matt Gemmell already shared this tip in a Twitter update.)