This IE demo uses dragstart/dragend: https://testdrive-archive.azurewebsites.net/Graphics/MagneticPoetry/Default.html

In Nightly this behaves incorrectly (try moving some words and compare to Chrome). Bisecting this, I noticed dragging did nothing at all until just a few weeks ago: bug 1552814.

However it's still buggy because the event has unexpected offsetX/offsetY values. See the attached minimal test case. When I drag the "drag me" span to the middle of the page, I get:

dragStart (39, 11)
dragEnd (-9, -10)

In Chrome and Safari I get something like this:

dragStart (35, 6)
dragEnd (845, 340)

I don't know what the correct behavior is, but our behavior does seem confusing to me.

Note that some investigation into this is probably going to be done in https://bugzilla.mozilla.org/show_bug.cgi?id=505521 (i wrote a testcase to compare the various drag events and their offset/page/screen coordinates there, along with some early findings on Chrome and Firefox interop).

(In reply to Thomas Wisniewski [:twisniewski] from comment #1)

Note that some investigation into this is probably going to be done in https://bugzilla.mozilla.org/show_bug.cgi?id=505521 (i wrote a testcase to compare the various drag events and their offset/page/screen coordinates there, along with some early findings on Chrome and Firefox interop).

Ah my Bugzilla searches somehow didn't find that bug. Thanks for working on this!

(cleared the needinfo, since whatever needs to happen to the dragevents should be done in bug 505521)