OS X Lion introduced new methods for resizing windows. Before Lion, you resized a window by either clicking the green traffic light in the window's upper left corner, or by dragging the bottom right corner of the window up or down, side to side, or diagonally. These methods worked fine for adjusting the basic size of a window, but most times, it was necessary to combine resizing with moving the window around, in order to get everything just the way you wanted it.
Anyone moving from the Windows OS probably found OS X's window resizing process both frustrating and a bit limiting. With the current Windows OS, you can resize a window from any edge. Apple finally saw the light and realized that Windows has some good ideas, such as the ability to resize a window from any edge.
With Lion or later, Apple took the plunge and provided the ability to resize a window by dragging any side or corner. This simple change lets you size a window by expanding or decreasing just the side of the window that needs a bit of adjusting. For example, if a window has some content just beyond its right-hand edge, just drag the right-hand side of the window a bit to see the entire content.
Resizing a Window
Move your cursor to any side of a window. As the cursor nears the edge of the window, it will change to a double-ended arrow. Once you see the double-ended arrow, click and drag to resize the window.
Resizing also works on the corners of a window, letting you resize in two directions at once by dragging diagonally at a window's corners. This is the standard window resize method that has been present in OS X since day one.
The new window resize feature is a nice addition, and an easy one to master. But Apple always offers an additional twist to keep things interesting.
Resizing All Sides of a Window
A nifty new trick is to resize all sides of a window at once. This keeps the window centered at its present location but allows you to increase or decrease the window size by expanding or shrinking all sides of the window at the same time.
To perform this trick, hold down the option key and then click and drag any of the corners of a window.
Resize Opposite Sides of a Window
The option key trick also works when you click and drag a window by either side or the top/bottom. Hold down the option key, and then click and drag the window by either side. The window will stay centered while opposite sides expand or contract in relation to your mouse movements.
Still More Secrets of Window Resizing
So far, we've seen that you can resize a window in Lion using any edge, as well as any corner. If you hold down the option key, you can also resize a window by expanding or decreasing opposite sides of a window at the same time. This method keeps the window centered at its present location while you adjust its size.
Control Aspect Ratio As You Resize a Window
The option key isn't the only key that holds some magic for window resizing; the shift key does, too. If you hold down the shift key while you expand or contract a window, the window will maintain its original aspect ratio.
For example, if the window originally had a 16:9 aspect ratio, and you wish to maintain that same ratio of width to height, simply hold down the shift key before you drag any of the window's edges. The edge opposite the one you are dragging from will remain stationary, while the other edges will expand or contract to retain the current aspect ratio.
The shift key can also be very handy for anyone working with windows that contain photographs, video, or other images.
Combining Both Shift and Option Keys
Using the option+shift keys simultaneously produces a subtle difference in how the resizing is performed. Just as when using the shift key alone, the aspect ratio will be maintained as you drag an edge or corner. In addition, instead of one edge remaining stationary, the window will remain centered at its current location, while all window edges change to maintain the aspect ratio.
With so many resizing options available, chances are that at least one of them will fill your needs. So, remember: Resizing a window isn't just a drag; it's also an option, shift, or option+shift drag.