Re: [Usability] Using checkbuttons, but needing three states...

[Matthew Thomas <mpt myrealbox com>]

On 2 Oct, 2005, at 6:14 PM, Vincent Untz wrote:
> ...
> In GConf, there can be three states for a boolean key: true, false and
> unset. Most of the times, we don't care about unset since if the key is
> unset, a default value will be used. But with pessulus, that's a
> different matter: it can configure a mandatory value for a key. Eg, it
> can set the mandatory value of /apps/epiphany/lockdown/disable_history
> to TRUE to force the disabling of history of epiphany, to FALSE to 
> force the use of history. And if it sets this key to unset, then the 
> user will be able to choose what he wants.
>
> So the three states are useful. But how can I do this with checkbuttons
> in a non-confusing way?

You can't, really. Use three radio buttons if you have the space, or if 
you don't, an option menu with three items.

> I can set the checkbutton to the "inconsistent" state if the key is 
> unset, but I feel it's confusing and not really understandable.

Indeed. The inconsistent state for a checkbox means "partly on and 
partly off", not "I don't care". :-)

Don't feel bad that an apparently-boolean setting can't be presented 
using a checkbox; sometimes they're inappropriate even for 
genuinely-boolean settings. Checkboxes should be used only for things 
that are obviously on/off, so it's obvious what the other option is. 
Otherwise, you should use radio buttons or an option menu. (For 
example, the Gimp's preferences have a checkbox for "Use 'Dot for dot' 
by default". Since it's not obvious what the alternative is, this 
option -- if it is necessary at all -- should instead use radio buttons 
to make the alternative explicit.)

--
Matthew Paul Thomas
http://mpt.net.nz/