Re: tree view column sizing problem

[Allin Cottrell <cottrell wfu edu>]

Just for the record, if anyone else hits this.

> I wrote:
> > I have a tree view with 3 columns, which sits within a scrolled 
> > window.  
> > 
> > The middle column contains what can be quite a lengthy string. 
> > When the user opens the window in question, I'd like her to be 
> > visually aware that the third column is there: the problem is that 
> > with the columns autosized, the length of the middle string can 
> > push the third column out of the visible zone (you have to scroll 
> > horizontally to reach it).
> 
> > The ideal solution, I think, would be (a) set the starting width 
> > of the middle column to some reasonable maximum (when the window 
> > is first opened), but then (b) allow the user to expand it to read 
> > the full string if need be.

Dave Howorth responded:

> If the user can be satisfied with seeing one complete string at a time,
> another option is to add a full-width label widget at the bottom of the
> window showing the content of the second column of the currently
> selected row. That avoids the need for the user to resize anything.
> 
> Or add tooltips to the column.

I tried tooltips (well, a hand-rolled tooltip using gtk_window, 
since the current gtk tooltips API doesn't work with treeview 
cells), but it was a lot of work, and didn't really cut it.  

For example, if the user maximizes the window on a big screen, we 
_really_ don't want to artificially restrict the width of the big 
second column, and only show its full content via an auxiliary 
popup.

My solution: check the widths in the process of creating the 
window.  If the middle column is going to push the third column 
into the non-visible zone, restrict its width with 
gtk_tree_view_column_set_max_width().  But also -- and this makes 
the whole thing work -- add a callback to motion-notify-event for 
the treeview: 

static gboolean 
big_col_callback (GtkWidget *w, 
                 GdkEventMotion *e, 
                 gpointer p)
{
    GtkTreeViewColumn *col = 
	gtk_tree_view_get_column(GTK_TREE_VIEW(w), 1);

    if (gtk_tree_view_column_get_max_width(col) > 0) {
	/* remove the width constraint */
	gtk_tree_view_column_set_max_width(col, -1);
    }

    return FALSE;
}

The effect is that column 1 starts at a size that allows the third 
column to be visible, but as soon as the user moves the mouse in 
the treeview window, the column becomes freely resizable.

Allin Cottrell