I don't see clientX and clientY props in the built-in debugger. STR: 1) use the attached code snippet example 2) create a breakpoint on the console.log line 3) Break in the debugger 4) check the 'Function Scope' section and expand the 'Event' object 5) clientX and clientY are not there function test(event) { console.log(event); } <button onclick="test(event)">Click Me</button> Note that the properties are visible if the object is inspected using Web Console. Honza

I've put your test code here: http://htmlpad.org/native-desc/ The reason these properties don't show up is that Debugger.Object.getOwnPropertyDescriptor throws NS_ERROR_XPC_BAD_OP_ON_WN_PROTO: http://mxr.mozilla.org/mozilla-central/source/toolkit/devtools/debugger/server/dbg-script-actors.js#1184 In the log I see this error for the following properties of MouseEvent: type,target,currentTarget,eventPhase,bubbles,cancelable,timeStamp,defaultPrevented,which,rangeParent,rangeOffset,pageX,pageY,isChar,screenX,screenY,mozMovementX,mozMovementY,clientX,clientY,ctrlKey,shiftKey,altKey,metaKey,button,buttons,relatedTarget,mozPressure,mozInputSource I don't know the cause of this error or how to work around it, but hopefully Jim or Jason would have some ideas.

This seems to be caused by bug 560072. It would be nice if we could come up with a workaround, because that bug doesn't seem easy to fix.

Note that bug 792215 will change the weird accessor properties on the prototype into ordinary accessor properties. The mouse events will still display as property-less objects whose prototypes have accessors on them, though, which is unfortunate. It might be possible to use hostAnnotations to tell the debugger when to display such things. That's a proposed mechanism for objects' classes to give Debugger metadata about instances. Draft spec for hostAnnotations: https://github.com/jimblandy/DebuggerDocs/tree/onNewGlobal

This *may* get fixed by bug 830818.

(In reply to Panos Astithas [:past] from comment #4) > This *may* get fixed by bug 830818. Surprise, it didn't! Bug 776864 is needed too, from what I can tell.

(In reply to Panos Astithas [:past] from comment #5) > (In reply to Panos Astithas [:past] from comment #4) > > This *may* get fixed by bug 830818. > > Surprise, it didn't! > Bug 776864 is needed too, from what I can tell. ...or more accurately, bug 851073. Which was just fixed! \o/

(In reply to Panos Astithas [:past] from comment #6) > ...or more accurately, bug 851073. Which was just fixed! \o/ A million times \o/