Important changes in the last commit that may break things

[Benoît Minisini <benoit.minisini@xxxxxxxxxxxxxxxx>]

Hi,

The last commits introduce big changes that may break the look of your 
application and make you cry.

I added two new properties in the Style class, 'BackgroundShape' and 
'SelectionShape', to define the roundness of the background and 
selection frames. From fully square to very round.

Now I'm modyfing the controls so that they follow these properties.

I added two options in the IDE that allow to change these properties on 
the fly.

I rewrote all containers of the 'Panel' family in Gambas too. And let 
'Panel' use the new background system when its Border property is 
'Raised', 'Sunken' or 'Etched'. Not very backward-compatible I admit.

The implementation of round borders is very tricky, as toolkits mostly 
don't support that (parent controls always clip their children with 
rectangles).

All that is work in progress, and may change a lot. But I wanted you to 
see that as early as possible so that I can have your remarks and 
questions before disrupting everything.

Once done, the second step may be written some new controls that mimic 
the ones made by the Gnome project in libadwaita.

That way, you will be able to write applications with the 'Gnome' look 
as well as with the 'KDE' look with Gambas.

Regards,

--
Benoît Minisini.