[whatwg] DragEvent's inherited MouseEvent properties should be available to all drag events

Sebastian Markbåge sebastian at calyptus.eu
Wed Jul 22 12:54:53 PDT 2009

The spec should explicitly specify which MouseEvent properties are available
during the various drag events to avoid assumptions.

Gecko currently sets pageX, clientX, screenX etc. to zero on the source node
events (drag, dragend).

As far as I know there are no known security flaws surrounding this
implementation. Browsers allow positioning values outside the browser window
on mousemove events during a mousedown + mousemove operation.


This issue is related to whether or no a DragEvent is infact a MouseEvent.
The current drag specifies that "User agents must, every 350ms (±200ms),
perform the following steps in sequence.." It doesn't make sense to trigger
this event if nothing has changed based on time alone. If something moves in
front of it or behind it, it may need to be triggered again, but a user
agent should be able to decide whether or not that's a possibility.

All current implementations trigger this sequence faster if the mouse is
moving. Effectively treating mouse movements as new drag events. Just like

IMO, it should be specified that mouse movements triggers a new iteration of
this sequence, and that current mouse position should be a part of the

The specification is only partly input device agnostic. It can't be both
totally input device agnostic and inherit MouseEvent. If it's going to
inherit MouseEvent it needs to be specified what that means.


(This is a repost because the first two was blocked by mod filter, hopefully
this doesn't become a double post.)
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