Re: drag and drop with clist

[Dan Espen <dane mk telcordia com>]

Dan Espen <dane mk telcordia com> writes:
> Hi,
>
> I'm trying to use drag and drop in a Clist with GtkPerl 1.2.10.
>
> The approach I've taken so far is:
>
> $clist->set_reorderable($true);
> $clist->signal_connect('drag_begin', \&DragBegin );
> $clist->signal_connect('drag_end', \&DragDrop );
>
> sub DragBegin {
>   my ($bw, $context) = @_;
>   my ($x,$y) = $bw->get_pointer();
>   my $adjy=$y-71;                     # size of titles fixme
>   ($row_drag_from) = $bw->get_selection_info($x, $adjy);
> }
>
> sub DragDrop {
>   my ($clist_widget, $drag_context, $selectiondata, $info, $time) = @_;
>   my ($x,$y) = $clist_widget->get_pointer();
>   my $adjy=$y-47;                     # size of titles fixme
>   my ($row) = $clist_widget->get_selection_info($x, $adjy);
>   print "move from $row_drag_from to $row\n";
> }
>
> The "set_reorderable" part works fine, I can drag items in the clist.
> I need to know the row dragged from and to to be able to reorder
> my application data.
> The technique I'm using is to get the pointer position and then
> use get_selection_info to convert that pointer position into a
> row number.
>
> One problem is that get_selection_info wants the pointer position to
> be relative to the Clist data, but get_pointer is relative to the Clist
> including the title.
> I looked at the logic in Mandrake's MenuDrake
> (which is written in C and it gets
> the position of the row like this:
>
>   y -= (GTK_CONTAINER (clist)->border_width +
>       widget->style->ythickness +
>       clist->column_title_area.height);
> #define ROW_TOP_YPIXEL(clist, row) (((clist)->row_height * (row)) + \
>                                   (((row) + 1) * CELL_SPACING) + \
>                                   (clist)->voffset)
>   dest_info.cell.row = ROW_FROM_YPIXEL (clist, y);
>
> So, MenuDrake seems to be subtracting things like border widths
> and title heights to adjust the pointer value before using it
> to index the row.
>
> Is there any way to access things like the border width or clist title
> height from gtk perl?
>
> The pointer value at DragBegin is interesting.
> I did some debugging and the pointer values were always like this:
>
> Row Pointer
> 0   71
> 1   95
> 2  119
>
> but if I drag upward, the pointer values run like this:
>
> Row Pointer
> 0   47
> 1   71
> 2   95
>
> The numbers are always 24 apart, regardless of where the pointer
> is at the start of the drag.
> Whats weird is the different numbers depending on the direction.
> I guess the number comes from when the pointer crosses some
> boundary.
> I suppose I can deal with that by delaying the calculations
> until the drop and adjusting the numbers based on the
> drop location being lower than the drag location, but that
> seems like a weird thing to have to do.
>
> Its also a bit strange, using xmag, it looks like the 47 includes the clist
> title but not the border which doesn't match up with Menudrake.
> I haven't studied Menudrake too closely maybe I'm misreading it.
> Its also working with a Ctree which might be somewhat different.
>
> I've seen earlier discussions of this in these 2 threads:
>
> http://mail.gnome.org/archives/gtk-perl-list/2002-May/msg00111.html
> http://mail.gnome.org/archives/gtk-perl-list/2002-March/msg00028.html
>
> but the way the threads concluded, it didn't seem like there
> was a satisfactory conclusion.
>
> Am I misunderstanding the correct approach?
> Does the above information seem correct?
>
> I really need to get the title height into my calcuations, I don't
> want to hard code a number, because I assume the title height will
> vary depending on the font being used.
>
> Thanks in advance for any help.

Well, sorry for what appears to have been a dumb question.
I never did get an answer, but being persistent,
I eventually ran across the "row_move" callback which
solved all my problems.

Thanks anyway.
-- 
Dan Espen                           E-mail: dane mk telcordia com