simplify the layout calc state
fix typo in setSizes
update base Widget to control absolute positioning
update splitter to use base widget positioning
add IPoint and IRect
update splitter example
ws commit
update tabbar for new positioning
update tab bar example
add box sizing to widget
add box sizing to geometry module
cleanup box sizing and add sum fields
cleanup splitter size hinting
ensure tab position is never negative
rename private method
tweak example css
handle child layout
add child layout support
ws commit
update tabwidget example