Struct Constraint

pub struct Constraint { /* private fields */ }

Constraint 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 Constraint 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 Constraint instance are immutable after creation.

Properties

constant

The constant value to be added to the source-attribute.

Readable | Writeable | Construct Only

multiplier

The multiplication factor to be applied to the source-attribute.

Readable | Writeable | Construct Only

relation

The order relation between the terms of the constraint.

Readable | Writeable | Construct Only

source

The source of the constraint.

The constraint will set the target-attribute property of the target using the source-attribute property of the source.

Readable | Writeable | Construct Only

source-attribute

The attribute of the source read by the constraint.

Readable | Writeable | Construct Only

strength

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.

Readable | Writeable | Construct Only

target

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.

Readable | Writeable | Construct Only

target-attribute

The attribute of the target set by the constraint.

Readable | Writeable | Construct Only

Implements

[trait@glib::ObjectExt]

GLib type: GObject with reference counted clone semantics.

Implementations

impl Constraint

pub fn new( target: Option<&impl IsA<ConstraintTarget>>, target_attribute: ConstraintAttribute, relation: ConstraintRelation, source: Option<&impl IsA<ConstraintTarget>>, source_attribute: ConstraintAttribute, multiplier: f64, constant: f64, strength: i32, ) -> Constraint

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

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

Returns

the newly created constraint

pub fn new_constant( target: Option<&impl IsA<ConstraintTarget>>, target_attribute: ConstraintAttribute, relation: ConstraintRelation, constant: f64, strength: i32, ) -> Constraint

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

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

Returns

the newly created constraint

pub fn builder() -> ConstraintBuilder

Creates a new builder-pattern struct instance to construct Constraint objects.

This method returns an instance of ConstraintBuilder which can be used to create Constraint objects.

pub fn constant(&self) -> f64

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

Returns

a constant factor

pub fn multiplier(&self) -> f64

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

Returns

a multiplication factor

pub fn relation(&self) -> ConstraintRelation

The order relation between the terms of the constraint.

Returns

a relation type

pub fn source(&self) -> Option<ConstraintTarget>

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.

Returns

the source of the constraint

pub fn source_attribute(&self) -> ConstraintAttribute

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

Returns

the source’s attribute

pub fn strength(&self) -> i32

Retrieves the strength of the constraint.

Returns

the strength value

pub fn target(&self) -> Option<ConstraintTarget>

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.

Returns

a ConstraintTarget

pub fn target_attribute(&self) -> ConstraintAttribute

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

Returns

the target’s attribute

pub fn is_attached(&self) -> bool

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

Returns

TRUE if the constraint is attached

pub fn is_constant(&self) -> bool

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

Returns

TRUE if the constraint is a constant relation

pub fn is_required(&self) -> bool

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

Returns

true if the constraint is required

Trait Implementations

impl Clone for Constraint

fn clone(&self) -> Self

Makes a clone of this shared reference.

This increments the strong reference count of the object. Dropping the object will decrement it again.

fn clone_from(&mut self, source: &Self)

Performs copy-assignment from source.

impl Debug for Constraint

fn fmt(&self, f: &mut Formatter<'_>) -> Result

Formats the value using the given formatter.

impl Default for Constraint

fn default() -> Self

Returns the “default value” for a type.

impl HasParamSpec for Constraint

type ParamSpec = ParamSpecObject

type SetValue = Constraint

Preferred value to be used as setter for the associated ParamSpec.

type BuilderFn = fn(_: &str) -> ParamSpecObjectBuilder<'_, Constraint>

fn param_spec_builder() -> Self::BuilderFn

impl Hash for Constraint

fn hash<H>(&self, state: &mut H)

where H: Hasher,

Hashes the memory address of this object.

fn hash_slice<H>(data: &[Self], state: &mut H)

where H: Hasher, Self: Sized,

Feeds a slice of this type into the given Hasher.

impl Ord for Constraint

fn cmp(&self, other: &Self) -> Ordering

Comparison for two GObjects.

Compares the memory addresses of the provided objects.

fn max(self, other: Self) -> Self

where Self: Sized,

Compares and returns the maximum of two values.

fn min(self, other: Self) -> Self

where Self: Sized,

Compares and returns the minimum of two values.

fn clamp(self, min: Self, max: Self) -> Self

where Self: Sized,

Restrict a value to a certain interval.

impl ParentClassIs for Constraint

type Parent = Object

impl<OT: ObjectType> PartialEq<OT> for Constraint

fn eq(&self, other: &OT) -> bool

Equality for two GObjects.

Two GObjects are equal if their memory addresses are equal.

fn ne(&self, other: &Rhs) -> bool

Tests for !=. The default implementation is almost always sufficient, and should not be overridden without very good reason.

impl<OT: ObjectType> PartialOrd<OT> for Constraint

fn partial_cmp(&self, other: &OT) -> Option<Ordering>

Partial comparison for two GObjects.

Compares the memory addresses of the provided objects.

fn lt(&self, other: &Rhs) -> bool

Tests less than (for self and other) and is used by the < operator.

fn le(&self, other: &Rhs) -> bool

Tests less than or equal to (for self and other) and is used by the <= operator.

fn gt(&self, other: &Rhs) -> bool

Tests greater than (for self and other) and is used by the > operator.

fn ge(&self, other: &Rhs) -> bool

Tests greater than or equal to (for self and other) and is used by the >= operator.

impl StaticType for Constraint

fn static_type() -> Type

Returns the type identifier of Self.

impl Eq for Constraint