Performance Metrics

Measuring rendering and runtime performance.

Key Metrics

Frame Budget

16ms frame budget:
├─ Event handling: 2ms
├─ State update: 1ms
├─ Layout: 3ms
├─ Paint: 5ms
├─ GPU submit: 3ms
└─ Buffer: 2ms

Measuring Performance

use std::time::Instant;

fn measure_frame<F: FnOnce()>(f: F) -> Duration {
    let start = Instant::now();
    f();
    start.elapsed()
}

Bundle Size

Memory Usage

Performance Score

fn performance_score(metrics: &PerfMetrics) -> f32 {
    let frame_score = if metrics.frame_time_ms < 16.0 { 100.0 }
        else { (16.0 / metrics.frame_time_ms) * 100.0 };

    let size_score = if metrics.bundle_kb < 500.0 { 100.0 }
        else { (500.0 / metrics.bundle_kb) * 100.0 };

    frame_score * 0.6 + size_score * 0.4
}

Profiling

#[cfg(feature = "profiling")]
fn profile_layout(tree: &mut WidgetTree) {
    let start = Instant::now();
    tree.layout();
    log::trace!("Layout: {:?}", start.elapsed());
}

Verified Test

#[test]
fn test_performance_frame_budget() {
    // 60fps = 16.67ms per frame
    let target_fps = 60.0;
    let frame_budget_ms = 1000.0 / target_fps;

    assert!((frame_budget_ms - 16.67).abs() < 0.01);

    // Frame time check
    let actual_frame_ms = 12.5;
    let meets_budget = actual_frame_ms <= frame_budget_ms;
    assert!(meets_budget);

    // Calculate actual FPS
    let actual_fps = 1000.0 / actual_frame_ms;
    assert_eq!(actual_fps, 80.0);  // 12.5ms = 80fps
}