This CL improves the method by which excess space is distributed in GridLayout.
Previously, GridLayout would assume weights were arranged in a 'line' and
sum the weights in the assumed line to figure out the proportional allocation
to each view. The system involved running GridLayout's internal constraint
solver twice.
Behavior was unspecified (and surprising) when weights appeared in views
that were not linked together linearly, typically leaving the last view
in each axis with more space than expected (in GridLayout's Bellman-Ford
constraint solver, remaining space goes to the last span of the axis).
This CL changes the weight distribution mechanism to effectively integrate it
with the Bellman-Ford constraint resolution algorithm. It does this
by returning a boolean value from the constraint solver saying whether or
not the constraints could be solved and then using a binary chop to find
a maximum amount of space that can be distributed without violating the
constraints.
This implementation runs the solver log(<axis size> * <number of Views>)
times until finding the maximum amount of space that can be distributed according
to the weights without causing a contradiction. We expect the cost of this
variation to be around a factor of 10 worse than the previous implementation
but to provide a simple and general definition of space distribution via
weights that will be open to many future optimizations.
As a side effect, this CL also fixes a bug in GridLayout where remaining space
was distributed only along the major axis.
Bug: 17485996
Change-Id: I120f39e95e90b5b35072ef8a6c348ec541aae42a
98d5f04f91