Constraint#

class Constraint(**properties: Any)#

Superclasses: Object

Describes a constraint between attributes of two widgets,

expressed as a linear equation.

The typical equation for a constraint is:

target.target_attr = source.source_attr × multiplier + constant

Each GtkConstraint is part of a system that will be solved by a ConstraintLayout in order to allocate and position each child widget or guide.

The source and target, as well as their attributes, of a GtkConstraint instance are immutable after creation.

Constructors#

class Constraint
classmethod new(target: ConstraintTarget | None, target_attribute: ConstraintAttribute, relation: ConstraintRelation, source: ConstraintTarget | None, source_attribute: ConstraintAttribute, multiplier: float, constant: float, strength: int) → Constraint#

Creates a new constraint representing a relation between a layout attribute on a source and a layout attribute on a target.

Parameters:

  • target – the target of the constraint

  • target_attribute – the attribute of target to be set

  • relation – the relation equivalence between target_attribute and source_attribute

  • source – the source of the constraint

  • source_attribute – the attribute of source to be read

  • multiplier – a multiplication factor to be applied to source_attribute

  • constant – a constant factor to be added to source_attribute

  • strength – the strength of the constraint

classmethod new_constant(target: ConstraintTarget | None, target_attribute: ConstraintAttribute, relation: ConstraintRelation, constant: float, strength: int) → Constraint#

Creates a new constraint representing a relation between a layout attribute on a target and a constant value.

Parameters:

  • target – a the target of the constraint

  • target_attribute – the attribute of target to be set

  • relation – the relation equivalence between target_attribute and constant

  • constant – a constant factor to be set on target_attribute

  • strength – the strength of the constraint

Methods#

class Constraint
get_constant() → float#

Retrieves the constant factor added to the source attributes’ value.

get_multiplier() → float#

Retrieves the multiplication factor applied to the source attribute’s value.

get_relation() → ConstraintRelation#

The order relation between the terms of the constraint.

get_source() → ConstraintTarget | None#

Retrieves the ConstraintTarget used as the source for the constraint.

If the source is set to NULL at creation, the constraint will use the widget using the ConstraintLayout as the source.

get_source_attribute() → ConstraintAttribute#

Retrieves the attribute of the source to be read by the constraint.

get_strength() → int#

Retrieves the strength of the constraint.

get_target() → ConstraintTarget | None#

Retrieves the ConstraintTarget used as the target for the constraint.

If the targe is set to NULL at creation, the constraint will use the widget using the ConstraintLayout as the target.

get_target_attribute() → ConstraintAttribute#

Retrieves the attribute of the target to be set by the constraint.

is_attached() → bool#

Checks whether the constraint is attached to a ConstraintLayout, and it is contributing to the layout.

is_constant() → bool#

Checks whether the constraint describes a relation between an attribute on the target and a constant value.

is_required() → bool#

Checks whether the constraint is a required relation for solving the constraint layout.

Properties#

class Constraint
props.constant: float#

The constant value to be added to the source_attribute.

props.multiplier: float#

The multiplication factor to be applied to the source_attribute.

props.relation: ConstraintRelation#

The order relation between the terms of the constraint.

props.source: ConstraintTarget#

The source of the constraint.

The constraint will set the target_attribute property of the target using the source_attribute property of the source.

props.source_attribute: ConstraintAttribute#

The attribute of the source read by the constraint.

props.strength: int#

The strength of the constraint.

The strength can be expressed either using one of the symbolic values of the ConstraintStrength enumeration, or any positive integer value.

props.target: ConstraintTarget#

The target of the constraint.

The constraint will set the target_attribute property of the target using the source_attribute property of the source widget.

props.target_attribute: ConstraintAttribute#

The attribute of the target set by the constraint.