On Thu, 20 Nov 2003 14:14:57 -0600
Michael Urman [EMAIL PROTECTED] wrote:
Thanks Walter and Doug for the wonderful TreeView DND example.
Finally I was able to go get the DND constraints I want in my
application.
But what I still can't figure out is how to communicate these to the
user. There must be a way to tell GTK that i can't drop from that
source row to this dest row, so the DND doesn't look like it's going
to happen.
I've tried connected 'drag-motion' events and conditionally calling
drag_context.set_reply(False, time) from it. Which does nothing until
i kill the normal handler, but then it just stops all drops.
http://www.moeraki.com/pygtkreference/pygtk2reference/class-gtktreedragdest.html
row_drop_possible() looks like the right idea, but i don't know how to
hook it up. Any suggestions?
If you want to talk in tested code, i have a base available at
http://mu.arete.cc/treeviewdnd.py ; in that example i'd like to make
it so you can only drop a row on a row of a preceding letter, but not
do this by filtering in drag_data_received.
I suppose you are asking two questions:
1. how to tell gtk, that you can't drop to a certain row.
2. how to communicate that to the user before the drop occurs.
1. how to tell gtk
1.1 static parentability
if the rows that could not be made parents are unchangeably set (e.g
bookmarks organized in a tree or menus in a menueditor for a
windowmanager) one could use an extra column with boolean values. (apply
the appended diff to Dougs version. the resulting code is ugly and needs
tidying up but shows the principle. you won't get the seventh row to be
a parent any more.)
1.2 dynamic parentability
I think it is not difficult to implement - comparing values of certain
cells.
2. how to communicate to the user
2.1 static parentability
placing a descriptiv graphic (i.e a foldericon) somewhere/somehow in the
row would probably do the trick.
2.2 dynamic parentability
there are two decisions to make:
a) what kind of (temporary) visual changes
a1) a graphic in a small column, that shows up.
a2) changing the textcolor of a row/cell
a3) changing the color of a row
a4) placing a descriptiv graphic (i.e. a stop sign) at the row (a
transparent one would be nice). this would be the most appealing
possibility but very probably the most catchy too.
b) _when_ to show up the visual changes
b1) when the drag begins. that implies that the visual changes
occours for all rows not to be made parent. it seems like a sound
approach but may turn out to be too recource hungry.
b2) when the drag-icon is hovering over the row. (seems to be a
hairy one)
My aim here was mainly to clarify the possible decisions concerning the
user interface. it is surely not complete and inaccurate at some points
but may be helpful. I did not put much stress on coding difficulties
that may show up.
walter
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