Variables and Position

The most basic class for a solvable value is Variable. It acts a lot like a float, which makes it easy to work with.

Next to that there’s Position, which is a coordinate (x, y) defined by two variables.

To support connections between variables, a MatrixProjection class is available. It translates a position to a common coordinate space, based on Item.matrix_i2c. Normally, it’s only Ports that deal with item-to-common translation of positions.

class gaphas.solver.Variable(value: SupportsFloat = 0.0, strength: int = 20)

Representation of a variable in the constraint solver.

Each Variable has a value and a strength. In a constraint the weakest variables are changed.

You can even do some calculating with it. The Variable always represents a float variable.

The variable decorator can be used to easily define variables in classes.

add_handler(handler: Callable[[Variable, float], None]) → None

Add a handler, to be invoked when the value changes.

remove_handler(handler: Callable[[Variable, float], None]) → None

Remove a handler.

notify(old: float) → None

Notify all handlers.

property strength: int

Strength.

dirty() → None

Mark the variable dirty in all attached constraints.

Variables are marked dirty also during constraints solving to solve all dependent constraints, i.e. two equals constraints between 3 variables.

Variables can have different strengths. The higher the number, the stronger the variable. Variables can be VERY_WEAK (0), up to REQUIRED (100). Other constants are WEAK (10) NORMAL (20) STRONG (30), and VERY_STRONG (40).

gaphas.solver.variable(strength=20, varname=None)

Easy-to-use drop Variable descriptor.

>>> class A(object):
...     x = variable(varname='_v_x')
...     y = variable(STRONG)
...     def __init__(self):
...         self.x = 12
>>> a = A()
>>> a.x
Variable(12, 20)
>>> a._v_x
Variable(12, 20)
>>> a.x = 3
>>> a.x
Variable(3, 20)
>>> a.y
Variable(0, 30)

class gaphas.position.Position(x, y, strength=20)

A point constructed of two Variable’s.

>>> vp = Position(3, 5)
>>> vp.x, vp.y
(Variable(3, 20), Variable(5, 20))
>>> vp.pos
(Variable(3, 20), Variable(5, 20))
>>> vp[0], vp[1]
(Variable(3, 20), Variable(5, 20))

class gaphas.position.MatrixProjection(pos: Position, matrix: Matrix)