Struct BackdropPlanner 

pub struct BackdropPlanner { /* private fields */ }

Turns a painted scene’s layer and draw events into a FramePlan.

Fed by a backend as it walks the scene. Costs nothing at all until the first backdrop op arrives: a page with no glass on it never allocates and never computes a bounding box.

Implementations

impl BackdropPlanner

pub fn new() -> Self

pub fn is_tracking(&self) -> bool

Whether the planner is currently tracking anything.

A backend checks this before computing a bounding box to hand to draw: while it is false, that box would be discarded, and computing one per draw command is exactly the per-frame CPU cost this whole design exists to avoid.

pub fn push_layer(&mut self, bounds: Rect)

Record a layer push whose clip bounds everything drawn until its pop.

Accounting content at the layer rather than per draw is what keeps this affordable. A panel’s whole subtree is clipped to the layer, so one bounding box covers all of it however many commands it contains.

pub fn pop_layer(&mut self)

pub fn draw(&mut self, bounds: Rect)

Record a draw issued with no layer bounding it.

Only meaningful at or above the open batch’s depth; deeper draws are already covered by the layer they are inside. Backends should gate the call on is_tracking rather than compute a bounding box unconditionally.

pub fn backdrop( &mut self, filter: Arc<Filter>, clip: BezPath, bounds: Rect, ) -> Boundary

Record a backdrop-filtered layer that is about to be pushed.

Returns whether the scene has to be cut here. The op’s own bounds join the occupied region, so a second panel overlapping this one gets its own segment whether or not the backend also reports the layer push.

pub fn finish(self) -> FramePlan

Close the frame and hand back what it costs.

Trait Implementations

impl Debug for BackdropPlanner

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

Formats the value using the given formatter.

impl Default for BackdropPlanner

fn default() -> BackdropPlanner

Returns the “default value” for a type.