[Design] Design + Usability, Useful + Usable

[Phillip J. Eby]

At 11:21 AM 12/13/2007 -0600, Matthew Eernisse wrote:
>Hank,
>
>The single big functional difference between iCal and the Chandler 
>collection selector is a requirement that we added to make it easier 
>for people who aren't overlaying multiple collections: You shouldn't 
>have to click twice to navigate between collections.

That's not incompatible with using checkboxes as the affordance for 
overlays.  If you select a collection whose box is not checked, we 
could show a greyed-out checkmark in the box, and when you click on 
another collection, that checkmark could go away.

If you select a collection that's already checked, navigating on or 
off of it would leave it unchanged.


>For the selection-override, you could simply check-and-disable the 
>checkbox to indicate that it's showing and can't be un-shown, and 
>then return it to its previous state when selection goes elsewhere. 
>This is what the first prototype I linked to in my previous e-mail does:
>
>http://www.fleegix.org/demo/floss_usability_2007/proto_1.html
>
>There are two drawbacks to this design:
>
>1. The disabled checkbox tells you nothing about what the state was 
>before the user selected the collection (and hence, what it will go 
>back to if the user selects something else).
>2. The user can't change it (from 
>visible-only-by-virtue-of-being-selected to visible). To change it, 
>the user would have to select a different collection.

I don't see either of these drawbacks if you use a greyed-out 
checkmark in the box, but leave the *box* enabled for 
clicking.  Here's the state map:

* Selected (highlighted) collection: clicking the box switches 
between a solid checkmark and a greyed checkmark (that will go away 
if you deselect the collection)

* Unselected collections: clicking the box switches between a solid 
checkmark and an empty box.

This is consistent and easy to predict, without requiring any new 
symbols to be invented.  If there is a column header like "Show" over 
the column of checkboxes, then the meaning should be apparent as soon 
as you notice the greyed checkmark moving when you select different 
collections.