Crate damage_rects 

Accumulate dirty rectangles and emit minimal redraw regions for partial GPU canvas updates.

Every interactive GPU-rendered app has a choice: redraw the whole frame every tick, or track which regions changed and redraw only those. The first is simple but wastes power; the second is what editors, design tools, terminals, and dashboards actually do.

This crate is the bookkeeping — you call DamageTracker::add when state changes, and at frame time you ask for the union of pending regions via DamageTracker::merged. It has no opinion on your coordinate system, no viewport tracking, and no GPU dependency — pairs with any 2D renderer (Skia, wgpu, raw Metal, softbuffer).

Example

use damage_rects::{DamageRect, DamageTracker};

let mut tracker = DamageTracker::new();

// during state updates:
tracker.add(DamageRect::new(10.0, 20.0, 100.0, 30.0)); // a line changed
tracker.add(DamageRect::new(50.0, 30.0, 80.0, 40.0));  // cursor moved

// at frame time:
if let Some(redraw_region) = tracker.merged() {
    // render(redraw_region.x, redraw_region.y, redraw_region.width, redraw_region.height)
    tracker.clear();
}

Full-damage shortcut

Some events invalidate the whole viewport (window resize, theme switch). Call DamageTracker::mark_full and subsequent DamageTracker::merged returns None; consult DamageTracker::is_full and render the whole viewport in that case. The flag prevents collecting individual rects you don’t need.

Structs

DamageRect

An axis-aligned rectangle in f32 space. Coordinate system is up to the caller — the library treats y as “down” only in the sense that DamageRect::bottom returns y + height.

DamageTracker

Accumulates dirty rectangles across a frame and emits a merged redraw region at frame time.