Struct Diagnostics 

#[non_exhaustive]
pub struct Diagnostics {
    pub test_commits_issued: usize,
    pub fb_delta_fast_path: bool,
    pub budget_exhausted: bool,
}

What one allocation pass did.

Fields (Non-exhaustive)

Non-exhaustive structs could have additional fields added in future. Therefore, non-exhaustive structs cannot be constructed in external crates using the traditional Struct { .. } syntax; cannot be matched against without a wildcard ..; and struct update syntax will not work.

test_commits_issued: usize

TEST_ONLY commits issued while probing for a viable assignment.

1 in steady state — warm re-validation of the cached assignment. Higher when the cache misses and the full search has to preseed, greedy, and backtrack. 0 when the FB-only fast path skipped re-validation.

fb_delta_fast_path: bool

Whether the cached allocation was reused and the TEST_ONLY skipped because only content changed on already-placed layers.

Implies test_commits_issued == 0 for the frame. This is the counter invariant 4 is stated in terms of.

budget_exhausted: bool

Whether the per-frame test-commit budget ran out before every layer had been offered a plane.

The budget bounds how many round trips to the kernel one frame may cost. Spending it is not an error – the layers it could not reach fall through to composition and still reach the screen – but it is a capacity limit rather than a hardware one, and the two look identical in layers_composited. On a device with many planes and a scene of spatially disjoint layers, each layer forms its own group costing one test commit, so a 17-layer scene exhausts the default budget of 16 and composites its last layer with a free, compatible plane sitting unused. Without this flag that reads as “the hardware ran out of planes”.

Trait Implementations

impl Clone for Diagnostics

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 Diagnostics

impl Debug for Diagnostics

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

Formats the value using the given formatter.

impl Default for Diagnostics

fn default() -> Self

Returns the “default value” for a type.

impl Eq for Diagnostics

impl PartialEq for Diagnostics

fn eq(&self, other: &Self) -> bool

Equality operator ==.

fn ne(&self, other: &Rhs) -> bool

Inequality operator !=.

impl StructuralPartialEq for Diagnostics