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.
When the solver is finalized with existing
constraints, we end up with criticals when
the constraints ref finalize code calls
back into the hash table. Avoid that by
emptying the hash table beforehand.
GtkConstraintSolver is an implementation of the Cassowary constraint
solving algorithm:
http://constraints.cs.washington.edu/cassowary/
The Cassowary method allows to incrementally solve a tableau of linear
equations, in the form of:
x = y × coefficient + constant
with different weights, or strengths, applied to each one.
These equations can be used to describe constraints applied to a layout
of UI elements, which allows layout managers using the Cassowary method
to quickly, and efficiently, lay out widgets in complex relations
between themselves and their parent container.
