Safe keyboard shortcut for activating code completion style functionality in Mac OS X browsers

Question

I'm building some code completion style text expansion functionality for text areas and inputs in a web application. I'm trying to work out a safe keyboard shortcut for invoking the completion proposals for browsers running on Mac OS X.

I've eliminated some potential candidates:

• Command+Space - activates the Spotlight search field
• Control+Space - activates the context menu in Firefox
• Escape - cancels any background XMLHttpRequests in Firefox

That leaves Option+Space. I'm aware that may conflict with tools like Ubiquity, but that's something we don't expect our audience to be using.

Are there any conflicts I may have missed with Option+Space? Or do you have a better idea for a keyboard shortcut, and why?

Answer 1

As I recall, Visual Studio and TextMate both use tab to code-complete. In Visual Studio an intellisense menu pops up as you start typing and tab acts as the selection confirmation.

In TextMate, you start typing part of a command then hit tab to activate said command's associated "bundle". The associated bundle typically generates a code snippet and fills in any dynamic parts of the snippet as you type.

Come to think of it, most command lines work this way as well, auto-completing file names and paths when tab is pressed after typing a few characters.

EDIT: You say tabs are needed for field switching in a web interface, but you may want to try intercepting the keyboard event in the textfield, and check if they're started typing a macro. If they have, auto-complete and swallow the key by returning false; if not, simply let the command bubble through.

Answer 2

I re-assigned the Spotlight command to Command+Shift+Space. This is easily done via Prefrences.App

Answer 3

Some kind of tab shortcut sounds like the best and most intuitive approach - users should be used to the 'type-tab-type-tab' workflow - maybe combine it with a modifier if it only wants to be optional.

Answer 4

A lot of Mac OS X apps use Option+Esc to do code completion or code hints.

Answer 5

I discussed these ideas with our design team. One of them suggested using Control+Enter, which is what we decided to go with. This causes forms that only contain a single input field to automatically submit in Firefox, but we deal with that by preventing the default action caused by the event.