On 16/08/2009, at 5:51 AM, Iceberg-Dev wrote:
When the drop is validated in the right window (type of item
accepted), I would like to either display a window above the right
window or change the right window content to give the user a list of
more detailed possible drop locations.
Something like this:
+-------------------+ +-------------------+
+-------------------+ +--------+----------+
| | | | |
| +-----+ | | | |
| | A | | | Left | Right |
| +-----+ | | | |
| | | | |
+-------------------+ +--------+----------+
There's something like this in Final Cut Pro (http://www.geniusdv.com/news_and_tutorials/assets_c/2009/04/superimpose3-thumb-394x397-2264.gif
).
Question:
---------
How could this be achieved in Cocoa?
I have tried with a window but the target of the drop does not get
changed.
Firstly I'd advise you to think whether a more straightforward design
is possible. Drag/Drop is inherently a mouse-targeted operation, where
there is a distinct end point to act as a drag target. If you haven't
got that, maybe drag/drop isn't an appropriate way to handle the
desired operation. In addition, regardless of FCP doing it, the user
isn't expecting a jack-in-the-box to leap out at the last second and
present a whole bunch of options - the target should be there from the
start.
Nevertheless, if you did insist on ploughing this furrow, I can think
of ways it can be done.
Design your target window/views so that they can be quickly switched
between the 'normal' and 'drop target' modes. How you do this is up to
you, for example with a split pane that opens to reveal the additional
'drop targets' section. Design, Build and Test this separately from
the drag/drop code. Once working to your satisfaction, integrate it
with the NSDraggingDestination protocol. Rather than reveal the
targets at drop time, it would be better to reveal them on drag enter,
so that the user can see the targets available while they're dragging,
and have plenty of time to a) choose a destination simply by dragging
to it, and b) giving them a chance to choose nothing after all, by
backing off (and thus drag leaving should close the drop targets pane).
I wouldn't try opening a window underneath the drop - it's kludgey,
unlikely to work and is not a nice behaviour for the user.
--Graham
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