Re: Preventing a drag in draggingSourceOperationMaskForLocal: not working
Re: Preventing a drag in draggingSourceOperationMaskForLocal: not working
- Subject: Re: Preventing a drag in draggingSourceOperationMaskForLocal: not working
- From: Corbin Dunn <email@hidden>
- Date: Fri, 22 Sep 2006 16:11:53 -0700
I'm trying to implement horizontal dragging in an NSTableView cell
(the same
sort of functionality iTunes provides when setting song ratings),
but am
having some problems. I have overridden the
draggingSourceOperationMaskForLocal: method in an NSTableView subclass
(which has been set as the custom class in the nib) to do the
following:
- (NSDragOperation)draggingSourceOperationMaskForLocal:(BOOL)isLocal;
{
// If we're in one of the "no-drag" columns (set in mouseDown:)
don't
allow a drag to occur
if (!_horizontalMotionCanBeginDrag)
{
return NSDragOperationNone;
}
return [super draggingSourceOperationMaskForLocal:isLocal];
}
The value for _horizontalMotionCanBeginDrag is set in mouseDown:, by
checking if the mouse cursor is in one of the table columns we want to
disable drags in:
- (void)mouseDown:(NSEvent *)event
{
BOOL mouseInNoDragColumns = ([[[self
mouseTableColumnForEvent:event]
identifier] isEqualToString:@"columnA"] ||
[[[self
mouseTableColumnForEvent:event]
identifier] isEqualToString:@"columnB"]);
// If we're in a "no-drag" column, flag it
_horizontalMotionCanBeginDrag = !mouseInNoDragColumns;
[super mouseDown:event];
}
---
When I try and perform a "horizontal" drag in those particular
cells, I can
see NSDragOperationNone being returned from the
draggingSourceOperationMaskForLocal: method. Despite this, a drag
image is
still produced (and a drag occurs, as writeRows: in the delegate is
called).
According to the docs, this is what I should be doing to prevent a
drag from
this row.
That's too late to do it. From a table, do this in your delegate:
- (BOOL)tableView:(NSYourTableView *)tableView writeRowsWithIndexes:
(NSIndexSet *)rowIndexes toPasteboard:(NSPasteboard*)pboard {
if ([tableView canDrag]) { ... stuff } else { return NO; }
}
set the "canDrag" in the subclass of your tableview (NSYourTableView)
with mouseDown: code similar to what you have.
I understand this is difficult to do and something like this will be
made easier to do in the future.
thanks,
--corbin
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