78033 - D&D from external Windows apps does not handle apps that only support "copy" operations

Status: VERIFIED FIXED

(Core :: XUL, defect, P4)

Description

[Mark Hammond [:markh] [:mhammond]]

Some Windows apps that support D&D only support "move" operations, and 
not "copy".  Windows D&D comminucates this through IDropTarget::DragEnter, 
where *pdwEffect is a mask of the supported operations.

Mozilla ignores this flag, and always sets the d&d type based exclusively on 
the keystate.  Thus, if a d&d operation is started from such an application and 
Ctrl is not held down, Mozilla still requests a copy, and the operation fails.  
If the Mozilla d&d operation is done with Ctrl held down, then Mozilla also 
treats it as a move, and the operation succeeds.

Attaching a patch to correct this behaviour.  Mozilla now first believes the 
source application, and will only attempt a "copy" operation if the source 
supports it.

Comment 1

[Mark Hammond [:markh] [:mhammond]]

Attachment: Proposed patch

Comment 2

[Blake Ross]

Looks okay to me, -> pink for module owner review.

Comment 3

[Mike Pinkerton (not reading bugmail)]

the existing code explicitly requests a "move" unless control is held down, then 
it requests a copy. are you sure you don't have the wording of this bug 
backwards? It seems to me that apps that only support "copy" won't work unless 
you hold down control.

am i confused?

Comment 4

[Kathleen :Brade]

Mark Hammond--Please clarify exactly which applications (on which platforms) you 
see a problem and where you are dropping what kind of data.  (QA will need to 
know for verification purposes).

Comment 5

[Mark Hammond [:markh] [:mhammond]]

My mistake - the wording was back to front.  If the app only supports "copy" we 
fail.

I am seeing this on all versions of Windows.  One example is the Perforce 
source-control system.  Presumably, this app believes that allowing a "move" 
from its source repository is a bad thing ;-)

I have observed it with at least one other app, but for the life of me I can't 
remember it.  However, the MS docs on this are pretty clear, and the current 
behaviour is certainly broken.

Comment 6

[Mark Hammond [:markh] [:mhammond]]

I was just a little quick - the behaviour can also be observed with WinCVS.

Comment 7

[Peter Trudelle]

->0.9.2/P4

Comment 8

[Peter Trudelle]

Doesn't fit the profile for 0.9.2, but might be able to get the fix in for
'limbo'.  ->0.9.3/helpwanted.

Comment 9

[Mike Pinkerton (not reading bugmail)]

r=pink/sr=hyatt. i'll check in when 0.9.4 opens. tested copy/move with mail and 
bookmarks and dragging a link to the desktop.

Comment 10

[Mike Pinkerton (not reading bugmail)]

checked in.

Comment 11

[Mark Hammond [:markh] [:mhammond]]

Works for me on the trunk.  ->VERIFIED.  Thanks!