When we call keypress which uses the synthesizeKey function from the EventUtils.js module we get an exception if the target element is not visible. It's not really understandable what's going on. A more meaningful failure should be logged. Currently we get: Error: [Exception... "Component returned failure code: 0x80004005 (NS_ERROR_FAILURE) [nsIDOMWindowUtils.sendKeyEvent]" nsresult: "0x80004005 (NS_ERROR_FAILURE)" location: "JS frame :: file:///Volumes/data/build/mozmill/trunk/mozmill/extension/resource/modules/EventUtils.js :: synthesizeKey :: line 326" data: no] Source File: file:///Volumes/data/build/mozmill/trunk/mozmill/extension/resource/modules/frame.js Line: 411 Mikeal said on IRC that he wants to fix it right away.
Fixed in r476.
Looks good. And I was wrong. The exception will be thrown for non-existent widgets and not for hidden ones. Sorry for my false interpretation.