Trait LayoutModifierNode 

pub trait LayoutModifierNode: ModifierNode {
    // Provided methods
    fn measure(
        &self,
        _context: &mut dyn ModifierNodeContext,
        measurable: &dyn Measurable,
        constraints: Constraints,
    ) -> LayoutModifierMeasureResult { ... }
    fn measure_hold(
        &self,
        _density: f32,
        _constraints: Constraints,
        _size: Size,
        _wrapped: WrappedHold,
    ) -> Option<ConstraintsHold> { ... }
    fn min_intrinsic_width(
        &self,
        measurable: &dyn Measurable,
        height: f32,
        _density: f32,
    ) -> f32 { ... }
    fn max_intrinsic_width(
        &self,
        measurable: &dyn Measurable,
        height: f32,
        _density: f32,
    ) -> f32 { ... }
    fn min_intrinsic_height(
        &self,
        measurable: &dyn Measurable,
        width: f32,
        _density: f32,
    ) -> f32 { ... }
    fn max_intrinsic_height(
        &self,
        measurable: &dyn Measurable,
        width: f32,
        _density: f32,
    ) -> f32 { ... }
}

Marker trait for layout-specific modifier nodes.

Layout nodes participate in the measure and layout passes of the render pipeline. They can intercept and modify the measurement and placement of their wrapped content.

Provided Methods

fn measure( &self, _context: &mut dyn ModifierNodeContext, measurable: &dyn Measurable, constraints: Constraints, ) -> LayoutModifierMeasureResult

Measures the wrapped content and returns both the size this modifier occupies and where the wrapped content should be placed.

The node receives a measurable representing the wrapped content and the incoming constraints from the parent.

Returns a LayoutModifierMeasureResult containing:

• size: The final size this modifier will occupy
• placement_offset_x/y: Where to place the wrapped content relative to this modifier’s top-left corner

For example, a padding modifier would:

• Measure child with deflated constraints
• Return size = child size + padding
• Return placement offset = (padding.left, padding.top)

The default implementation delegates to the wrapped content without modification (size = child size, offset = 0).

NOTE: This takes &self not &mut self to match Jetpack Compose semantics. Nodes that need mutable state should use interior mutability (Cell/RefCell).

fn measure_hold( &self, _density: f32, _constraints: Constraints, _size: Size, _wrapped: WrappedHold, ) -> Option<ConstraintsHold>

The incoming constraints the last measure of this node, which gave size under constraints, holds for: every constraints inside give the same result. wrapped is what the content this node wraps measured. None, the default, holds for constraints alone; a node that tells must give the range its own measure keeps its result and hands its content constraints that wrapped holds for.

fn min_intrinsic_width( &self, measurable: &dyn Measurable, height: f32, _density: f32, ) -> f32

Returns the minimum intrinsic width of this modifier node. The default is the wrapped content’s, for a node that keeps the content’s size.

fn max_intrinsic_width( &self, measurable: &dyn Measurable, height: f32, _density: f32, ) -> f32

Returns the maximum intrinsic width of this modifier node. The default is the wrapped content’s, for a node that keeps the content’s size.

fn min_intrinsic_height( &self, measurable: &dyn Measurable, width: f32, _density: f32, ) -> f32

Returns the minimum intrinsic height of this modifier node. The default is the wrapped content’s, for a node that keeps the content’s size.

fn max_intrinsic_height( &self, measurable: &dyn Measurable, width: f32, _density: f32, ) -> f32

Returns the maximum intrinsic height of this modifier node. The default is the wrapped content’s, for a node that keeps the content’s size.

Dyn Compatibility

This trait is dyn compatible.

In older versions of Rust, dyn compatibility was called "object safety".

Implementors