A "better" way of resizing GtkTreeViewColumns... but how do I do it?

[kcirtap lavabit com]

Hi all,

I'm trying to create GtkTreeViewColumn resizing functionality like how it
is in Thunderbird. Key word here is "trying". So far I haven't succeeded.

The easiest way to understand how this resizing works is to fire up
Thunderbird and play with resizing the columns yourself, but basically the
way it works in Thunderbird is if you drag, say, column #1 to the right,
this increases the width of column #1, at the same time decreasing the
width of column #2 by the same amount. This happens until column #2
reaches its minimum width (for example, 0 pixels). At this point,
continuing to drag column #1 to the right still increases the width of
column #1, but since column #2 cannot be shrunken any further, then column
#3 is shrunken until it reaches its minimum width. This continues until
all of the columns to the right of column #1 are at their absolute minimum
widths; at this point, column #1 can't have its width increased anymore,
so continuing to drag the column to the right does nothing.

While the mouse button is still held down, if you were to start dragging
column #1 to the left again (to shrink it), what would happen is what
happened above, except in reverse order. As column #1 shrinks, the last
column in the tree view grows until reaching its width at the time the
original drag (when the mouse was first pressed down to start the drag)
first started. At this point, the second to last column grows until
reaching its width at the time of the original drag... and so on.

Then of course, when column #1 reaches its minimum width, column #0
shrinks until it reaches its minimum width. Since column #0 is the first
column, then continuing to drag column #1 to the left won't shrink it
anymore; in fact, nothing will happen.

One of the major benefits to handling dragging like this is: the columns
will never be resized "out of bounds" and cause the GtkTreeView to grow in
width or, if the GtkTreeView containing the GtkTreeViewColumns is packed
into a scrolled window, cause horizontal scrollbars to appear. Having
these scrollbars appear, or the tree view grow in width (and thus increase
the width of the window) is super annoying for the user and makes things
look a lot less clean. Which is, I assume, why Thunderbird handles it this
way, as do other applications.

So, anyway, my problem is that I just can't figure out how to do this in
GTK+. I'm wondering if it's even possible? If it is, would someone be able
to create a working example for me? I'd be willing to pay for this if
necessary.

As far as I know, the only signal you can connect to to know if a
GtkTreeViewColumn has been resized is the notify::width signal. Problem
is, you can't return TRUE or FALSE from the signal handler function to
tell GTK+ not to allow the resize to go through. It's just a notification
signal. So that prevents me from, for example, detecting that all columns
to the right of the one being dragged have reached their minimum widths
and then telling GTK+ to stop the column from having its width increased
anymore.

Another problem: if you call gtk_tree_view_column_set_fixed_width() --
what I am doing is calling gtk_tree_view_column_set_resizable(column,
TRUE) and then calling gtk_tree_view_column_set_sizing(column,
GTK_TREE_VIEW_COLUMN_FIXED) when creating the columns, by the way --
within the notify::width signal, it creates an infinite loop, which I
don't know how to prevent, either.

Again, any help would be much appreciated. Thanks!