Spring.ts

import { DrawnObjectBase } from "./DrawnObjectBase.js";
import { SizeConfig, SizeConfigLiteral } from "./SizeConfig.js";

//===================================================================
// Class implementing spring objects in a springs and stuts layout.
// These objects are designed to be placed between the content objects
// of a row or column and provide a stretchable or compressable space.
// See the Column class for the complete layout rules.
//
// These objects are fairly simple.  They produce no drawing (but a
// Spring_debug subclass has been provided below to provide a debugging
// display to make these normally invisible objects visible).  Their
// behavior is implemented by maintaining a fully stretchable size configuration
// (min=0 natural=0 max=infinite).

export class Spring extends DrawnObjectBase {
  public constructor() {
    super(0, 0, 0, 0, true);

    // configure to initially be fully elastic
    this._wConfig = SizeConfig.elastic(0);
    this._hConfig = SizeConfig.elastic(0);
  }

  //. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

  // Override w & h setters so they enforce elastic size
  public override get w() {
    return super.w;
  }
  public override set w(v: number) {
    //=== YOUR CODE HERE ===
    if (v !== this._w) {
      // don't forget to declare damage whenever something changes
      // that could affect the display
      //=== YOUR CODE HERE ===
      super.w = v;
    }
  }

  public override get h() {
    return super.h;
  }
  public override set h(v: number) {
    //=== YOUR CODE HERE ===
    if (v !== this._h) {
      // don't forget to declare damage whenever something changes
      // that could affect the display
      //=== YOUR CODE HERE ===
      super.h = v;
    }
  }

  //. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

  // Override configuration setters to enforce elastic with zero natural size
  public override get wConfig() {
    return super.wConfig;
  }
  public override set wConfig(v: SizeConfigLiteral) {
    super.wConfig = SizeConfig.elastic(0);
  }

  public override get hConfig() {
    return super.hConfig;
  }
  public override set hConfig(v: SizeConfigLiteral) {
    super.hConfig = SizeConfig.elastic(0);
  }
}

//===================================================================

export class Spring_debug extends Spring {
  // we explicitly declare a size here so we know how to draw
  public constructor(dir: "w" | "h") {
    super();
    // we give this a bit of size so the drawing we are doing is not clipped away
    this._direction = dir;
    if (dir === "w") this.h = this.hConfig.nat = 20;
    if (dir === "h") this.w = this.wConfig.nat = 20;
  }

  protected _direction: "w" | "h";

  protected override _drawSelfOnly(ctx: CanvasRenderingContext2D): void {
    ctx.save();

    // box around the outside
    ctx.strokeStyle = "black";
    ctx.strokeRect(0, 0, this.w, this.h);

    // spring-like lines (depending on direction)
    ctx.beginPath();
    ctx.moveTo(0, 0);
    if (this._direction === "w") {
      ctx.lineTo(this.w / 3, this.h);
      ctx.lineTo((2 * this.w) / 3, 0);
      ctx.lineTo(this.w, this.h);
    } else {
      ctx.lineTo(this.w, this.h / 3);
      ctx.lineTo(0, (2 * this.h) / 3);
      ctx.lineTo(this.w, this.h);
    }
    ctx.stroke();

    ctx.restore();

    super._drawSelfOnly(ctx);
  }
}

//===================================================================