Consider adding a component API

[Tyriar]

Initially discussed in #807 (comment)

This would involve adding some interface like this that would make implementing addons much easier:

interface IComponent {
  onRefresh(rows: CircularList, startIndex: number, endIndex: number): void
  onDraw(group: RenderGroup, element: HTMLElement): void
  onMousedown(evt: MouseEvent): void
  onMouseup(evt: MouseEvent): void
  onInput(evt: KeyboardEvent): void
  onFocus(): void
  onBlur(): void
  onScroll(): void
  onOpen(term: ITerminal): void
  onResize(rows: number, cols: number)
  // ...
}

Candidates for turning into components:

• CompositionHelper
• SelectionManager
• Search
• Linkifier

/cc @mofux

[Tyriar]

The internal IRenderLayer interface is pretty close to what I imagine the component API to look like:

export interface IRenderLayer {
  /**
   * Called when the terminal loses focus.
   */
  onBlur(terminal: ITerminal): void;

  /**
   * * Called when the terminal gets focus.
   */
  onFocus(terminal: ITerminal): void;

  /**
   * Called when the cursor is moved.
   */
  onCursorMove(terminal: ITerminal): void;

  /**
   * Called when options change.
   */
  onOptionsChanged(terminal: ITerminal): void;

  /**
   * Called when the theme changes.
   */
  onThemeChanged(terminal: ITerminal, colorSet: IColorSet): void;

  /**
   * Called when the data in the grid has changed (or needs to be rendered
   * again).
   */
  onGridChanged(terminal: ITerminal, startRow: number, endRow: number): void;

  /**
   * Calls when the selection changes.
   */
  onSelectionChanged(terminal: ITerminal, start: [number, number], end: [number, number]): void;

  /**
   * Resize the render layer.
   */
  resize(terminal: ITerminal, dim: IRenderDimensions, charSizeChanged: boolean): void;

  /**
   * Clear the state of the render layer.
   */
  reset(terminal: ITerminal): void;
}

Plus exposing the convenience methods on BaseRenderLayer to allow the easy creation of custom canvases

[parisk]

Looks neat.

Called when the data in the grid has changed (or needs to be rendered again).

Would it make sense to separate grind changing and the need for re-rendering, or are they the same thing?

[Tyriar]

RIght now they're the same thing, need to re-render is only fired on an animation frame. If we enabled third party addons we may need to reconsider.

[feamsr00]

Hi!
I'd have to say that I do like the direction where this is going as 1) Having a well-defined interface for internal and external components is a really good idea. 2) Specifically, I think I'm interested in adding a new render layer as well.

(Time and effort permitting) It might be wise to begin refactoring internal objects to follow a similar model so that more of XT is composable. While I admit it might mean a bit of a re-arch if you're already planning on making changes soon, doing this now might pay down a lot of technical (architectural) debt.

[Tyriar]

Closing in favor of #1128 (comment) which is the first step