Crate densa_draw 

A frame’s display list, independent of any GPU API.

Painters draw through a Canvas: filled rectangles and glyphs (from a shared densa_text::GlyphCache) become Instances in an InstanceBuffer, one quad each, in the vertex layout densa-render uploads and draws in a single instanced draw call. Keeping the list GPU-free makes every painter testable without a GPU, and lets other backends draw the same list.

Drawing allocates nothing once the frame’s glyphs are cached.

use densa_draw::{Canvas, Color, InstanceBuffer, Rect};
use densa_text::{AtlasConfig, GlyphCache};

// One glyph cache and one instance buffer per frame loop, reused every frame.
let mut cache = GlyphCache::new(AtlasConfig::default());
let mut instances = InstanceBuffer::with_capacity(1024);

let mut canvas = Canvas::begin(&mut cache, &mut instances);
canvas.fill_rect(Rect::new(0.0, 0.0, 200.0, 20.0), Color::srgb(0x202020));
let saved = canvas.state();
canvas.clip(Rect::new(0.0, 0.0, 100.0, 100.0));
// Cut to the clip on the CPU: the frame stays one draw call.
canvas.fill_rect(Rect::new(50.0, 0.0, 200.0, 20.0), Color::WHITE);
canvas.restore(saved);

assert_eq!(instances.len(), 2);
let cut = instances.as_slice()[1];
assert_eq!(cut.rect, [50.0, 0.0, 50.0, 20.0]); // x, y, width, height

Structs

Canvas

One frame being drawn: everything painters emit goes through it.

CanvasState

A canvas’s translation and clip, saved with Canvas::state and brought back with Canvas::restore.

Color

A color in linear RGB with straight (not premultiplied) alpha: the space densa blends in.

Instance

One quad, as read by the vertex shader (per-instance step mode).

InstanceBuffer

Fixed-capacity instance list rebuilt every frame without allocating.

Point

A position in pixels, y down.

Rect

An axis-aligned rectangle in pixels, y down, stored as its four edges.

Size

A width and a height in pixels.