Fixed issue #433 (layout sometimes ignores ratio)

[Vulcalien]

Since the bug is well explained in the issue, let's talk about the patch.

I studied this problem for a few hours.
Apparently, this bug always occurs when there are two terminals (horizontal or vertical, doesn't matter).
It also occurs when there are more than two, but I didn't figure out any logical pattern.

Technical details

Basically, while loading a layout, the function set_position_by_ratio indirectly calls new_size (through Gtk.main_iteration()) which calls self.set_position(self.get_position()).
Only after set_position is executed the position is actually set (inside set_position_by_ratio), based on the ratio.
But the problem is that set_position takes self.get_position() as argument, while it still hasn't been set. So it calculates the new ratio, which is always about 0.5.

Fix

Initially, I wanted to remove self.set_position(self.get_position()) from new_size, but that would break stuff. (When splitting a terminal, the ratio has to be calculated again because of that line of separation between the terminals).
So I instead just store self.ratio on a temp variable and restore the value after Gtk.main_iteration() has done.

[mattrose]

Thank you so much! I must admit I looked at that for a little while when it came in and it was not immediately obvious. I'll pull this down this evening and give it a once-over but you've explained very clearly what's gone wrong and how you fixed it, so I'm sure it'll get merged in very soon.

Thanks again!

[mattrose]

Works brilliantly. This seems to be the second hack around inconsistent GTK calls, and now I think I know why they're getting rid of the GTK.Container() class in GTK4. It does mean that paned.py will need to be re-written from scratch when we go to GTK4, but that will probably be a good thing.

[mattrose]

Any other bugs you feel like fixing? 😃

[Vulcalien]

Sure! I've plenty of time, I'll try to fix some stuff