Disable submit buttons if required items are not selected

[Ryan J Ollos <ryan.j.ollos@…>]

A feature initially discussed in #10994 is to disable Remove selected items and Add attachment buttons if no items have been selected - table entries for the former and a file for the latter. The feature might be implemented for some additional buttons while working on this ticket. The initial patch can be seen in ticket:10994:t10994-r11508-1.patch​. I'm targeting this to 1.0.2 per comment:9:ticket:10994.

[Ryan J Ollos <ryan.j.ollos@…>]

Patch against r11682 of the trunk.

[Ryan J Ollos <ryan.j.ollos@…>]

t11056-r11682-1.patch​ applies behavior to the Add attachment (/attachment/*), Change tickets (/query), Install (/admin/general/plugin) and Remove selected items (/admin/ticket/*, /admin/versioncontrol/repository, /admin/general/perm) buttons.

One particular behavior worth pointing out is that by clicking on the labels for the Subject or Group all of the checkboxes in the row are toggled. This is a nice convenience, but unfortunately I can't see a way to make it more obvious to the user.

There are some other places that similar behavior could be implemented. I've opted not to include these in the patch because I couldn't convince myself that they would necessarily improve usability, but I'm hoping to hear additional opinions:

• /newticket: Disable Create ticket until at least one character has been entered in the Summary (or disable if summary is greater than max_description_size).
• /search: Disable Search until at least min_query_length characters have been entered.
• /milestone?action=new: Disable Add milestone until at least one character has been entered for the Name of the milestone field.

The general criteria I took when deciding where to implement the button disabling is to disable a button if the user could be redirected to an error page by not selecting an item before submitting.