Struct ClipStack 

pub struct ClipStack { /* private fields */ }

The compiler’s clip stack: scissor rectangles and coverage masks, one stack.

Retained across frames like the strip generator it works beside — the mask context and the rewrite scratch are exactly the buffers a steady-state frame should be reusing. ClipStack::reset is what keeps it from carrying state between frames.

Implementations

impl ClipStack

pub fn new() -> Self

An empty stack, clipping nothing.

pub fn reset(&mut self)

Drop every clip and counter, keeping the buffers.

pub fn scissor_clips(&self) -> u32

Clips lowered to a scissor this frame.

pub fn mask_clips(&self) -> u32

Clips lowered to a coverage mask this frame.

pub fn mask_strips(&self) -> usize

Strips this frame’s coverage masks cost — zero for a frame whose clips all scissored.

pub fn mask(&self) -> Option<PathDataRef<'_>>

The mask a draw generated now has to be clipped against, or None when no mask is on the stack.

pub fn blocks_everything(&self) -> bool

Whether the current scissor admits nothing, so a draw need not be generated at all.

pub fn push_rect( &mut self, rect: Rect, transform: Affine, generator: &mut StripGenerator, )

Push a rectangular clip: a scissor when the composed transform admits one, a coverage mask otherwise.

pub fn push_rounded( &mut self, rect: Rect, radii: RoundedRectRadii, transform: Affine, generator: &mut StripGenerator, )

Push a clip with rounded corners.

Radii that are all square describe a plain rectangle, so such a clip takes the rectangular path and can still scissor: a caller spelling an unrounded clip through the rounded command pays nothing for the spelling.

pub fn pop(&mut self)

Pop the most recent clip.

A pop with nothing to pop is ignored. A display list is recorded by a widget tree that can be unbalanced, and an unbalanced pop must not be able to lift a clip a sibling still relies on — nor to underflow the mask context, which would be a panic on the frame path.

pub fn clip_run( &mut self, storage: &mut StripStorage, strip_start: usize, alpha_start: usize, )

Rewrite the strip run a draw just generated so nothing outside the scissor survives.

strip_start and alpha_start are storage’s two lengths from immediately before the draw generated, so everything past them belongs to this draw alone and can be replaced wholesale. The rewrite reclaims the coverage it drops — the original bytes are truncated away and only the kept ones re-appended — so a clipped frame’s alpha buffer stays proportional to what it actually paints.

A run that needs no change is left exactly as it was, which is the whole unclipped case and most of the clipped one.

Trait Implementations

impl Debug for ClipStack

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

Formats the value using the given formatter.

impl Default for ClipStack

fn default() -> Self

Returns the “default value” for a type.