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Re: Have there been recent changes in DnD?


From: Andreas Schik
Subject: Re: Have there been recent changes in DnD?
Date: Wed, 16 Jan 2008 11:49:32 +0100
User-agent: GNUMail (Version 1.2.0)

On 2008-01-14 13:10:17 +0100 Fred Kiefer <address@hidden> wrote:

> Andreas Schik wrote:
>> On 2008-01-10 21:46:38 +0100 Fred Kiefer <address@hidden> wrote:
>> 
>>> Andreas Schik wrote:
>>>> since I 'upgraded' to yesterdays SVN og GNUstep I do have problems
>>>> with DnD in GNUMail. Have there been any changes in the underlying
>>>> mechanisms making it necessary to change applications?
>>>> 
>>> The basic mechanism hasn't changed since April last year. What has
>>> changed a bit was the implementation for NSTableVie and NSTextView. 
>>> Are
>>> you using subclasses of these?
>> It looks like GNUMail is using a subclass of NSTableView in the mail
>> window. This table is the source of the operation. What I found out 
>> so
>> far is that the target of the operation (outline view) in the method 
>> -
>> outlineView:validateDrop:proposedItem:proposedChildIndex: receives
>> NSDragOperationNone in the NSDraggingInfo object ([info
>> draggingSourceOperationMask]), no matter which modifier I press down.
>> 
> 
> There has been one important change for dragging in NSTableView, which
> may affect that code in some way. Now there are different drag mask
> settings for local and non-local dragging. The later by default is set
> to NSDragOperationNone. This behaviour matches, as far as I know, what
> Apple is doing. But why would the drag view see this as a non-local 
> drag
> operation?
> 
> What you should do is debug into GSDragView (and it's subclass XX) to
> see, how the value for draggingSourceOperationMask is build up from
> dragMask (coming from the drag source) and operationMask (coming from
> the modifier keys). One of these two (most likely dragmask) must be 
> wrong.
Well, it is not a GNUMail problem, but a combination of GNUstep and
Camaelon.
Camaelon introduces a category for NSTableView that does not call the
(assumedly new) selector -_initDefaults: Hence, the local dragging
mask is 0. Fixing this remedies part of the problem. What remains is a
quite strange behaviour:
If I overlap the mailbox window and the mail window of GNUMail the
operation works. As soon as there is a gap between the windows, i.e.
the drag operation touches an external application, the operation
again fails. It looks like GSDragView does not recognize that it must
switch back from non-local to local operation. It did not debug this,
though, and probabyl won't have time today to do so. But this might
anyway help you to track it down.

Cheers,
Andreas



-- 
Mail: andreas dot schik at web dot de
Home: http://www.andreasheppel.de

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