This is very similar to Saki's LovCombo extension (http://www.extjs.com/forum/showthread.php?t=32692), however it extends TriggerField rather than ComboBox and uses a CheckboxGroup internally rather than templates.
- Supports mostly all the same config options as a regular combobox
- Works fine as a grid editor
- Supports keyboard navigation
- Tested in Chrome, FF, and IE8
getValue() will return data like 'value,value,value', and you can use setValue() similarly, ie. checkboxCombo.setValue('value,value,value');
As always, feedback is appreciated. Have fun with it!
Download is available at: http://code.google.com/p/extuxcheckboxcombo/
* UPDATE 12/30/2010 *
Minor bug fixes
Added template support to more closely mimic a regular combobox
Added support for a 'change' event which bubbles the change event from the CheckboxGroup
Incorporated changes submitted by @mitchellsimoens (Thanks Mitchell!)
* UPDATE 5/6/2010 *
Some minor speed enhancements
Moved code over to Google code
* UPDATE 4/22/2010 *
Fixed a couple bugs, corrected issues with maxHeight, and triggerAction = 'all'
Also now includes minified versions of the js and css files