Instead of playing games with mapping negative symbolic values to
positive ones, let's use the appropriate constants everywhere. This
allows us to use:
GTK_CONSTRAINT_STRENGTH_WEAK * 2
Or
GTK_CONSTRAINT_STRENGTH_STRONG + 1
In code using the public API.
We also store the strength values as integers, so we can compare them
properly, and only turn them into doubles when they are inserted into
the solver, just like every other variable.
The strength for the natural width can be used
as a tie-breaker to make instable systems behave
in a more predictable way. This can be seen
in the simple constraints demo in gtk-demo.
It makes more sense to treat the natural size
of both children and guides as stays, since
we want to meet these values as closely as we
can, under the circumstances.
This commit moves GtkConstraintGuide into its own
source files to avoid gtkconstraintlayout.c turning
too messy, adds max size properties and implements
getters and setters.
