Tristate Checkbox Thoughts

I've been searching around for details regarding the possible implimentation of a WebForms native tristate checkbox in HTML5, the discussions I have found (e.g. http://krijnhoetmer.nl/irc-logs/html-wg/20070914) revolve around how to submit an indeterminate state and exactly why a form would need to submit it.

In answer to the latter point I am developing software which shows a list of results within a query and one of the attributes is a boolean. In order to allow the user to paginate and filter the lists a tri-state checkbox is needed to allow the user to

"Show only true"
"Show only false"
"Show all"

The current solution to this is to use a SELECT to submit the user's preference but I would argue that in this instance a tristate (aligned with the grid's relevant column) would be clearer to the user.



Regarding the primary issue: how to submit the indeterminate value i  prefer the above discussions' solution of extra values to be sent in a manner similar to the following:

<input type="checkbox" name="filter" value="true" tristate="all">

therefore in the indeterminate case the form would submit "filter=all". If the user were to specify the "tristate" attribute it could in compliant UAs enable the trisate mode whilst being safely ignored in UAs that can only deal with standard checkboxes - thus allowing a degree of flexibility in implimentations across devices.


Hope this is useful to someone

Ric Hardacre
MS.Net Professional - HTML/CSS/JS Hacker since the dawn of the web :-)








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