A Zooming Thought for Interface Designers
Posted on July 30, 2007
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It’s a generally-accepted tenet of user interface design that a user interface should get in the way of the user as little as possible. I like to think of this as “doesn’t force the user to consciously think each time they use it”. The ability to use an interface without thinking about it is also known as “muscle memory”.
So why do so many applications wilfully get in the way of the user’s muscle memory?
Today’s “interface wtf?” is zooming. Many, many applications allow users to zoom in or out of their document. Many applications implement this feature quite well yet oddly many don’t, and it isn’t that complicated (cognitively that is).
I blame this poorlyness squarely on the application developers being developers, in that I suspect the poor-implementers have approached the issue from the perspective of the logical, rational, literal geek as opposed to that of the illogical, irrational, “just make it work” user.
Zooming in Mac applications almost uniformly uses the following keyboard shortcuts:
Zoom out: Cmd -
Zoom in: Cmd +
Excellent applications like Apple’s Preview implement this keyboard combination exactly as shown typographically: hold down the Command key and press the corresponding minus or plus sign and zoom out or zoom in.
Poor applications (I refrain from naming names to protect the guilty) implement this keyboard combination literally: hold down the Command and minus key to zoom out, hold down the Command and Shift and plus key to zoom in.
Zoom out, no shift. Zoom in, shift. Muscle memory, zero.
When I say the poor applications have implemented this literally I mean that the developer knows that typing a literal minus character on the keyboard requires no shift key to type (shift minus gives and underscore) whereas typing a literal plus key does require the shift key. Being the literal-minded, logical sorts that they are these developers promptly foist this convention on the user without stopping to consider that the user does not in fact want to type either a minur or a plus but wants to simply make their document change size.
In fact if the user manages to completely forget about the minus or plus signs entirely and simply muscle-learns which keys to hit then they’re in a whole world of happy. Throw the shift key into the mix and this can’t happen; it foils the user’s msucles.
Even worse, some offenders actually map Command + without the shift, which is Command =, to a different shortcut altogether. In the application in front of me at the moment Command = maps to “Show at 100%”, presumably because “equals” equates no modification, which means that if I’ve zoomed in to 25% then want to zoom back out to 50% and I forget to hold down the shift modifier I actually end up running through 25%, 100%, 75%, 50%. No world of happy there.
Its the small things really.