294844 - Html elements can still be dragged when mouse is outside the window

Status: REOPENED

(Core :: DOM: UI Events & Focus Handling, defect)

Description

[Martijn Wargers (dead)]

See upcoming testcase.
Afaik, you should not be able to interact with the content area, when the mouse
is outside the window.
So the draggable div in this testcase should not be dragging on when the mouse
is moved outside the content area.
This only happens when there is at least some text in the draggable div, with no
text at all, the bug doesn't happen.

Comment 1

[Martijn Wargers (dead)]

Attachment: testcase

Comment 2

[Frank Faubert]

FYI: Adding "-moz-user-select: none;" to the style for #sun fixes the problem.

Comment 3

[Jonathan Watt [:jwatt]]

I believe this is the correct behavior, and certainly it's what I want. When the mouse is pressed, mouse capture is engaged so that you can get mousemove and mouseup events that occur outside the window. Once the mouseup occurs, mouse capture is turned off. If this didn't happen then DHTML dragging scripts don't get the mouseup to end the drag if the mouse is released when the cursor is outside the window. This can cause all sorts of strange behavior.

Comment 4

[Frank Faubert]

It may be what you want, until you try to implement a cross-frame drag and drop application. ;)

Comment 5

[Martijn Wargers (dead)]

Yeah, there are probably scenarios where this is desired, but I think it would be better if it would happen in a controllable way, rather than by accident.

Comment 6

[Jonathan Watt [:jwatt]]

Frank: yeah, making something unselectable will "fix" this since that causes the function that does the mouse grabbing to return early:

http://bonsai.mozilla.org/cvsblame.cgi?file=mozilla/layout/generic/nsFrame.cpp&rev=3.667&mark=1781,1785-1786,1792-1793#1776

Note that capturing mouse events from outside the window is not necessarily the same thing as capturing events from outside a frame. I wonder if I would be happy if mouse events that occur outside the window caused an equivalent DOM event to be dispatched to the top level content document with the document object as the event's target, regardless of whether the capture-activating mousedown occurred in a subframe or not.

Martijn: I agree it would be nice if this was more controllable. I doubt it is possible to have this behavior happen automatically and still allow everyone to meet their use cases. Do you have any suggestions on how this might be done?