Struct ConstraintsTransform 

pub struct ConstraintsTransform {
    pub width: AxisConstraint,
    pub height: AxisConstraint,
    pub alignment: Alignment,
    pub report: bool,
}

What a ConstraintsTransformBox gives its child, per axis, and what it does about a child that comes back too big.

It is a small vocabulary rather than an arbitrary function of the space on offer, and that is a decision worth stating. The layout and the paint walk are two passes over the same tree, and only the first is told what the parent offered: by the time the walk lays the child out, the box has been sized to the child and the offer is not recoverable from it. A function of the offer could not be run again there — and a function run again on the wrong input answers plausibly, which is worse than not answering at all. Each of these three can be run again: a fixed number is itself, an unbounded axis is a question with no input, and an axis given as it came produced a child of exactly the box’s own size.

The reference’s transform is a closure, and every transform the reference itself ships is one of these three.

Fields

width: AxisConstraint

What the child is given across.

height: AxisConstraint

And down.

alignment: Alignment

Where a child smaller than the box sits in it.

report: bool

Whether a child that came out bigger than the box is reported as an overflow — the yellow and black band, in debug builds. On by default: a box that transforms its constraints is asking a question about what fits, and a silent answer is no answer.

Implementations

impl ConstraintsTransform

pub fn new() -> Self

Both axes as they came, which is the transform that does nothing.

pub fn width(self, width: AxisConstraint) -> Self

What the child is given across.

pub fn height(self, height: AxisConstraint) -> Self

What the child is given down.

pub fn alignment(self, alignment: Alignment) -> Self

Where a child smaller than the box sits in it.

pub fn report(self, report: bool) -> Self

Whether a child bigger than the box wears a band. Off is what a deliberate spill wants.

Trait Implementations

impl Clone for ConstraintsTransform

fn clone(&self) -> Self

Returns a duplicate of the value.

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

Performs copy-assignment from source.

impl Copy for ConstraintsTransform

impl Debug for ConstraintsTransform

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

Formats the value using the given formatter.

impl Default for ConstraintsTransform

fn default() -> Self

Returns the “default value” for a type.