Class Canvas2dBackend

constructor

• new Canvas2dBackend(): Canvas2dBackend

• Returns Canvas2dBackend

Readonlykind

beginFrame

• beginFrame(clear: boolean): void

• The same clear CanvasLayer.clearBitmap does, so the op stream is unchanged.

  Parameters

  • clear: boolean

  Returns void

destroy

• destroy(): void

• Release the context and any GPU resources. The pane removes the canvas.

  Returns void

drawSeries

• drawSeries(
      entry: RendererEntry,
      items: readonly DrawItem[],
      priceToY: (price: number) => number,
      barSpacing: number,
      dpr: number,
      style: SeriesStyle,
      rc: SeriesRenderContext,
  ): void

• Paint one series. Same contract as RendererEntry.draw minus the context: priceToY and items[].x are media px, and the renderer snaps to device pixels with dpr itself.

  items and the objects in it belong to the pane, which rewrites them in place the next time it draws this series, so a backend that keeps any of it past that (a batch held across frames, say) copies what it keeps.

  Parameters

  • entry: RendererEntry
  • items: readonly DrawItem[]
  • priceToY: (price: number) => number
  • barSpacing: number
  • dpr: number
  • style: SeriesStyle
  • rc: SeriesRenderContext

  Returns void

endFrame

• endFrame(): void

• Every call above drew straight to the canvas; there is nothing to flush.

  Returns void

mount

• mount(canvas: HTMLCanvasElement, ctx2d: null | CanvasRenderingContext2D): void

• Take the pane's base data canvas. ctx2d is the 2D context the pane already holds on it, when it holds one: the canvas-2D backend draws on exactly that object, so a frame is one context's op stream and not two contexts' interleaved. A backend that owns the canvas outright ignores it.

  Parameters

  • canvas: HTMLCanvasElement
  • ctx2d: null | CanvasRenderingContext2D

  Returns void

overlay2d

• overlay2d(): null | CanvasRenderingContext2D

• A 2D context for what the backend does not draw natively (grid, axes, primitives), or null when the backend paints those itself.

  Returns null | CanvasRenderingContext2D

resize

• resize(_widthPx: number, _heightPx: number, _dpr: number): void

• Nothing to do: the pane's CanvasLayer owns the backing store and sized it already. Re-sizing it here would clear a bitmap that was just painted.

  Parameters

  • _widthPx: number
  • _heightPx: number
  • _dpr: number

  Returns void