Struct PaintDamage 

pub struct PaintDamage {
    pub generation: u64,
    pub layout_generation: u64,
    /* private fields */
}

The regions of the document whose pixels differ from the previous frame.

Coordinates are document space: CSS pixels, with ancestor scroll offsets already applied, and without the paint scale or the viewport offset. A consumer working in device pixels multiplies by the scale it painted at.

Fields

generation: u64

Bumped once per resolve that found anything at all.

Cheaper than the regions for the coarse question. A consumer that only wants “is this the same frame as last time” compares this and never looks at the rectangles.

layout_generation: u64

Bumped once per resolve whose final box geometry differs from the previous resolved frame.

Unlike generation, repaint-only changes such as a colour update leave this counter alone. Debug and cache consumers can therefore distinguish layout changes from paint changes without treating observation itself as a mutation.

Implementations

impl PaintDamage

pub fn is_empty(&self) -> bool

Whether anything at all changed.

pub fn regions(&self) -> &[Rect]

The changed rectangles, in no particular order and possibly overlapping.

pub fn intersects(&self, region: Rect) -> bool

Whether any of it lands in region.

The question a cache asks: given the area a filter reads from, is what it read last time still valid? Touching edges do not count, for the same reason they do not in the backdrop planner: a change ending at x1 and a read starting at x1 share no pixel.

Trait Implementations

impl Clone for PaintDamage

fn clone(&self) -> PaintDamage

Returns a duplicate of the value.

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

Performs copy-assignment from source.

impl Debug for PaintDamage

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

Formats the value using the given formatter.

impl Default for PaintDamage

fn default() -> PaintDamage

Returns the “default value” for a type.