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| Title: SectorElement.ts |
| A port of the software Geometry Applet by |
| Author: David E. Joyce |
| Department of Mathematics and Computer Science |
| Clark University |
| Worcester, MA 01610-1477 |
| U.S.A. |
| |
| http://aleph0.clarku.edu/~djoyce/home.html |
| djoyce@clarku.edu |
| |
| Date: February, 1996. Version 2.0.0 May, 1997. |
| TypeScript Port: 2019, Nelson Brown, brownnrl@gmail.com |
| https://www.nelsonbrown.net/ |
+----------------------------------------------------------------------*/
import {GeomElement} from "../GeomElement";
import {PointElement} from "../point/PointElement";
import {PlaneElement} from "../plane/PlaneElement";
import {Midpoint} from "../point/Midpoint";
import {SlateCanvas} from "../../Slate";
export interface ISectorElementConstruction {
O: PointElement;
A: PointElement;
B: PointElement;
P: PlaneElement;
}
export class SectorElement extends GeomElement {
_Center : PointElement;
_A : PointElement;
_B : PointElement;
// A and B are two points on a circle with the given center
_P : PlaneElement; // plane of the circle
_angle : number = null;
// Face fill alpha — drives drawFace's globalAlpha independent of
// drawProgress (which drives the arc sweep). Default 1 keeps every
// existing render path identical. Mirrors Circle/Polygon (#86).
private _faceAlpha : number = 1;
set faceAlpha(value: number) {
this._faceAlpha = value < 0 ? 0 : (value > 1 ? 1 : value);
}
get faceAlpha(): number { return this._faceAlpha; }
constructor(isec?: ISectorElementConstruction) {
super();
this.dimension = 2;
if(isec != null) {
this._Center = isec.O;
this._A = isec.A;
this._B = isec.B;
this._P = isec.P;
}
}
radius() : number {
return this._Center.distance(this._A);
}
defined() {
return this._A.defined() && this._B.defined() && this._Center.defined();
}
// Here, we differ from the original implementation.
// Since A and B are on the circle, we find the midpoint M between them.
// Then we calculate a radius distance along the line from Center M
// as the "through" point.
_updateThroughPoint() : void {
let r = this.radius();
if(r == 0) { // degenerate circle
return;
}
this._angle = Math.atan2(this._B.y - this._A.y, this._B.x - this._A.x) -
Math.atan2(this._Center.y - this._A.y, this._Center.x - this._A.x);
let x = this._Center.x + Math.cos(this._angle/2) * r;
let y = this._Center.y + Math.sin(this._angle/2) * r;
}
drawEdge(c: SlateCanvas): void {
if (!this.visible && !this.shouldHighlight && this.emphasisAmount <= 0) return;
// Pick the highlight color BEFORE the null bail, matching the
// other element types (#81 / #86) — a zero-color sector can
// still render in the highlight stroke while emphasized or
// slide-highlighted, which is what lets invisible angle
// markers light up on demand.
const color = (this.emphasized || this.shouldHighlight)
? this.edgeHighlightColor
: this.edgeColor;
if (color == null || !this.defined()) return;
let ctx = c.getContext("2d") as CanvasRenderingContext2D;
ctx.strokeStyle = color;
{
const baseW = this.shouldHighlight ? 3 : 1;
ctx.lineWidth = (baseW + this.emphasisAmount * (6 - baseW)) * GeomElement.styleScale;
}
this._traceEdge(ctx, this.radius());
}
// Trace and stroke the edge at radius r. The sector's edge is its arc;
// a right-angle marker (#201) overrides this to draw the square corner
// instead, keeping the colour / width / visibility preamble above.
protected _traceEdge(ctx: CanvasRenderingContext2D, r: number): void {
ctx.beginPath();
let startAngle = Math.atan2(
this._A.y - this._Center.y,
this._A.x - this._Center.x);
let arcAngle = this._arcAngle();
// Partial sweep for slide-transition animation: the arc grows
// from the A arm toward the B arm as drawProgress goes 0 → 1.
// Default progress = 1 reproduces the full arc bit-for-bit — the
// original expression is kept for it so no golden can move.
//
// #172 — mid-sweep, scale the sweep ctx.arc actually traces, not
// the signed angle. For the arm order whose signed angle opposes
// the fixed direction, the drawn arc is the complement, and scaling
// the signed angle made it open as a full circle and shrink.
const acw = this._anticlockwise();
let from = startAngle, flag = acw, endAngle: number;
if (this.drawProgress >= 1) {
endAngle = startAngle + arcAngle;
} else if (!this.sweepReverse) {
endAngle = startAngle + (acw ? -1 : 1) * this._drawnSweep() * this.drawProgress;
} else {
// Grow from the B arm back toward A: the same arc, traced the
// other way. Start at B and go against the drawing direction.
from = Math.atan2(this._B.y - this._Center.y, this._B.x - this._Center.x);
flag = !acw;
endAngle = from + (acw ? 1 : -1) * this._drawnSweep() * this.drawProgress;
}
ctx.arc(this._Center.x, this._Center.y, r, from, endAngle, flag);
ctx.stroke();
}
// Mid-sweep only: grow the arc from the B arm toward A instead of from
// A toward B (#172). Set by A.Sector.sweep's `reverse` arg for the run
// and cleared on finalise; the finished arc is the same either way.
public sweepReverse: boolean = false;
// The sweep ctx.arc actually traces from the A arm to the B arm: a
// non-negative magnitude in the _anticlockwise() direction (#172).
//
// The direction is fixed and the angle is signed, so for one arm order
// the arc drawn is the COMPLEMENT of the signed angle. That is the
// original applet's contract — SectorElement.java normalises a negative
// sweep by adding 360° — and the author orders the arms to pick the
// side. Static renders are identical either way; this only decides how
// the animation gets there.
protected _drawnSweep(): number {
const a = this._arcAngle();
let s = this._anticlockwise() ? -a : a;
if (s < 0) s += 2 * Math.PI;
return s;
}
// The signed arc to sweep from the A arm to the B arm, in radians.
// Default is the minor signed angle (−π..π). AngleMarkerElement
// overrides this to optionally sweep the major (reflex) arc.
protected _arcAngle(): number {
return this._Center.angle(this._A, this._B, this._P);
}
// Sweep direction passed to ctx.arc. Fixed true for plain sectors /
// arcs (their authors order _A/_B for that). AngleMarkerElement
// flips it to draw the major arc between the same two rays for a
// reflex marker.
protected _anticlockwise(): boolean {
return true;
}
// Magnitude of the swept arc — used by A.Sector.sweep to size the
// animation duration to what's actually drawn (so a reflex marker
// doesn't sweep a big arc in a tiny time).
public arcSpan(): number {
// #172 — the DRAWN sweep, so the complement case (a 270° arc from
// a 90° signed angle) is timed for what it traces.
return this._drawnSweep();
}
// Trace the closed wedge path (arc + the two radii back to centre)
// into the current ctx path. Shared by the face fill and the flash
// overlay so they cover exactly the same region.
protected _traceWedge(ctx: CanvasRenderingContext2D, r: number): void {
let startAngle = Math.atan2(
this._A.y - this._Center.y,
this._A.x - this._Center.x);
let arcAngle = this._arcAngle();
let endAngle = startAngle + arcAngle;
ctx.beginPath();
ctx.arc(this._Center.x, this._Center.y, r, startAngle, endAngle, this._anticlockwise());
ctx.moveTo(this._Center.x, this._Center.y);
if(arcAngle <= 180.) {
ctx.lineTo(this._A.x, this._A.y);
ctx.lineTo(this._B.x, this._B.y);
} else {
ctx.lineTo(this._B.x, this._B.y);
ctx.lineTo(this._A.x, this._A.y);
}
ctx.lineTo(this._Center.x, this._Center.y);
}
// Whether the whole wedge should flash (fill with the highlight
// color) while emphasised. False for plain sectors/arcs — only
// angle markers light up their fill during a slide transition.
protected _flashFace(): boolean {
return false;
}
drawFace(c: SlateCanvas): void {
if (!this.visible && !this.shouldHighlight && this.emphasisAmount <= 0) return;
if (this.faceColor == null || !this.defined()) return;
// Face is independent of the edge sweep — always the full
// sector wedge, with alpha driven by the dedicated faceAlpha
// field (mirrors Circle/Polygon, #86). Default 1 preserves
// the fully-opaque behaviour for every non-animating consumer.
let a = this.faceAlpha;
if (a <= 0) return;
let ctx = c.getContext("2d") as CanvasRenderingContext2D;
let r = this.radius();
ctx.fillStyle = this.faceColor;
this._traceWedge(ctx, r);
if (a < 1) {
ctx.save();
ctx.globalAlpha = a;
ctx.fill();
ctx.restore();
} else {
ctx.fill();
}
// Transition flash: while emphasised (the animator bumps
// emphasisAmount to 1 during a sweep and fades it 1 → 0
// afterward), light the ENTIRE wedge with the highlight color,
// fading with the emphasis. Edge-only emphasis (stroke width /
// gold) already happens in drawEdge; this fills the area too.
if (this._flashFace() && this.emphasisAmount > 0) {
ctx.save();
ctx.fillStyle = this.faceHighlightColor;
ctx.globalAlpha = 0.55 * this.emphasisAmount;
this._traceWedge(ctx, r);
ctx.fill();
ctx.restore();
}
}
drawName(c: SlateCanvas): void {
}
drawVertex(c: SlateCanvas): void {}
rotate(pivot: PointElement, ac: number, as: number): void {}
translate(dx: number, dy: number): void {}
update(): void {
this._updateThroughPoint();
}
}
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