What are standard keys for zooming (in/out) behavior for a User Interface

We are developing an application that uses a plot to show data. We allow zooming in and out - no scrolling up and down is necessary.

Double click is used to zoom in, backspace to zoom out. + and - keys are zoom in and out

We have be开发者_Go百科en unable to standardize on up and down arrows - does an up arrow typically mean zoom in or zoom out?

We are writing the code to do the zoom and it is a UI question - if there is a better site, please migrate.

Double-click to zoom and backspace to zoom out do not seem like an intuitive choice.

I'd say that +/- would make sense as zoom keys, like browsers do, but only if you combined them with a CTRL modifier.

Arrow keys are an absolute no-no for zoom. Arrow keys mean move caret, or scroll when there is no caret. Never use them for zoom.

Ctrl + + / - and Ctrl "Mouse Wheel" are the common zoom keys for web browsers.

Image viewers/editors and other specialized software might omit the Ctrl modifier if zooming is a common operation...

I'm not sure why you're allowing so many different methods for zooming in and out; consistency with other applications would suggest that if your app doesn't do scrolling, the arrows shouldn't do anything at all.

If you insist, I'd use up arrow for zooming in (making things larger) and down arrow for zooming out. Up would correspond with + and down would correspond with -, I think that would be the least confusing.

When you get around to wondering what the scroll wheel should do, check this old Joel On Software thread: http://discuss.joelonsoftware.com/default.asp?design.4.630539.38

To add onto to all these good answers... the Microsoft magnifier (the one that comes for free with the Intellipoint software, as opposed to the one that comes with the OS) uses another scheme: once the magnifier is visible, if you hold down the scroll wheel for a second, then the scroll wheel up/down begins to control the zoom in/out. Before this second timeout, the scroll wheel functions normally for the current window.