This lets you force a specific window scale, this is needed
for mutter to be able to disable the scaling as it needs access
to unmangled X window/screen sizes. It can also be useful to
force a specific scale in e.g. tests.
This is for compatibility reasons. We want to change APIs that operate
on X11 objects to take the X11 objects as arguments. However, this would
break a lot of APIs and we'd like to avoid this, so we play this little
trick (we will use the same trick for the other X11 objects). Also,
gobject-introspection and other bindings can correctly attach the
functions to the correct types as it is the same scheme that GDK2 used
for pixmaps, windows and drawables.
For GTK 4, we will remove this trick, so apps should properly cast their
objects right now.
Unfortunately, I don't think there is a way to use
GDK_DISABLE_DEPRECATED or similar macros to check for proper type casts
while compiling ensure compatibility with future GDK versions. I'm free
to consider them though.
