Struct Canvas 

pub struct Canvas<'a> { /* private fields */ }

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

Canvas::begin starts the frame on both the instance list and the glyph cache, so the cache’s “used this frame” protection spans every painter of the frame: a glyph drawn by one painter cannot be evicted by the next. One glyph cache serves every painter of a frame loop and its updates feed one GPU atlas (densa_render::GpuRenderer).

Positions go through a translation and are clipped to a rectangle (see translate and clip); state and restore save and bring back both, as a widget does around its children. Clipping happens here, on each rectangle and glyph, so a frame stays one draw call.

Allocation-free once the frame’s glyphs are cached.

Implementations

impl<'a> Canvas<'a>

pub fn begin(cache: &'a mut GlyphCache, out: &'a mut InstanceBuffer) -> Self

Starts a frame: clears out and begins a frame on cache.

pub fn state(&self) -> CanvasState

The current translation and clip, to restore later.

pub fn restore(&mut self, state: CanvasState)

Brings back a translation and clip saved with state.

pub fn translate(&mut self, dx: f32, dy: f32)

Moves everything drawn from now on by dx, dy.

pub fn clip(&mut self, rect: Rect)

Draws from now on only inside rect (in current coordinates), within the current clip.

pub fn clip_rect(&self) -> Rect

The area drawing still shows in, in current coordinates; empty when everything is clipped away.

pub fn fill_rect(&mut self, rect: Rect, color: Color)

A filled rectangle.

pub fn draw_glyph( &mut self, font: &Font, glyph: GlyphId, px: f32, at: Point, color: Color, )

glyph of font at px pixels per em, its pen at at: x is the pen position (fractional: drawn at the nearest subpixel bin), y the baseline (rounded to a whole pixel).

Glyphs the cache cannot provide this frame are skipped (counted in its stats).

pub fn draw_run(&mut self, run: GlyphRun<'_>, origin: Point)

Every glyph of run, offset by origin.

pub fn cache(&self) -> &GlyphCache

The glyph cache this frame draws through.

pub fn instances(&self) -> &InstanceBuffer

The instances emitted so far this frame.

Trait Implementations

impl<'a> Debug for Canvas<'a>

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

Formats the value using the given formatter.