Themeable symbolic constant

[cacaodev]

A symbolic constant is the default value between 2 layout items in the Constraint based layout system.

For example, the default space between 2 sibling buttons, between a button and a label, between a button and its superview. The value can differ depending on the orientation (vertical or horizontal).

A private method for creating constraints with this special value will be added:
- constraintWithFirstAnchor:secondAnchor:relation:multiplier:symbolicConstant:

An internal object called CPSpace will take as input the 2 items, the anchor or orientation and compute the resolved constant based on the current theme.