task(D11): snap extensions - quadrant (4 circle quadrants), perpendicular (foot point from refPoint), tangent (both tangent points via acos), fromOffset helper

frontend/src/canvas/SnapEngine.ts

@@ -104,6 +104,16 @@ export class SnapEngine {
       if (this.config.modes.has('nearest')) {
         this.collectNearest(el, worldX, worldY, tol, candidates);
       }
+      // ── Task D11: erweiterte Snaps ──
+      if (this.config.modes.has('quadrant')) {
+        this.collectQuadrant(el, worldX, worldY, tol, candidates);
+      }
+      if (this.config.modes.has('perpendicular') && refPoint) {
+        this.collectPerpendicular(el, worldX, worldY, refPoint, tol, candidates);
+      }
+      if (this.config.modes.has('tangent') && refPoint) {
+        this.collectTangent(el, worldX, worldY, refPoint, tol, candidates);
+      }
     }
 
     // Intersection snap (between pairs)
@@ -124,7 +134,8 @@ export class SnapEngine {
 
     // Priority: endpoint > intersection > center > midpoint > nearest > grid
     const priority: Record<string, number> = {
-      endpoint: 0, intersection: 1, center: 2, midpoint: 3, nearest: 4, grid: 5,
+      endpoint: 0, intersection: 1, center: 2, quadrant: 3, perpendicular: 4,
+      tangent: 5, midpoint: 6, nearest: 7, grid: 8,
     };
 
     // Find best within tolerance — prefer higher priority if distances are close
@@ -234,6 +245,79 @@ export class SnapEngine {
     }
   }
 
+  /** Task D11: Quadranten-Punkte bei Kreis/Bogen (0/90/180/270). */
+  private collectQuadrant(el: CADElement, wx: number, wy: number, tol: number, out: SnapPoint[]): void {
+    const check = (x: number, y: number) => {
+      const d = Math.sqrt((wx - x) ** 2 + (wy - y) ** 2);
+      if (d < tol) out.push({ x, y, type: 'quadrant' });
+    };
+    if (el.type === 'circle' || el.type === 'arc') {
+      const r = (el.properties as Record<string, unknown>).radius as number | undefined ?? el.width / 2;
+      check(el.x + r, el.y); // 0
+      check(el.x, el.y + r); // 90
+      check(el.x - r, el.y); // 180
+      check(el.x, el.y - r); // 270
+    }
+  }
+
+  /**
+   * Task D11: Perpendicular-Fußpunkt — der Punkt auf einem Segment,
+   * an dem die Verbindung zum refPoint SENKRECHT auf dem Segment steht.
+   */
+  private collectPerpendicular(
+    el: CADElement,
+    wx: number, wy: number,
+    refPoint: { x: number; y: number },
+    tol: number,
+    out: SnapPoint[],
+  ): void {
+    const p = el.properties as Record<string, unknown>;
+    const segs: Array<Array<{ x: number; y: number }>> = [];
+    if (
+      p.x1 !== undefined && p.y1 !== undefined &&
+      p.x2 !== undefined && p.y2 !== undefined
+    ) {
+      segs.push([{ x: p.x1 as number, y: p.y1 as number }, { x: p.x2 as number, y: p.y2 as number }]);
+    } else if (Array.isArray(p.points)) {
+      const pts = p.points as Array<{ x: number; y: number }>;
+      for (let i = 0; i < pts.length - 1; i++) segs.push([pts[i], pts[i + 1]]);
+    }
+    for (const [a, b] of segs) {
+      const foot = this.nearestOnSegment(refPoint.x, refPoint.y, a.x, a.y, b.x, b.y);
+      const d = Math.sqrt((wx - foot.x) ** 2 + (wy - foot.y) ** 2);
+      if (d < tol) out.push({ x: foot.x, y: foot.y, type: 'perpendicular' });
+    }
+  }
+
+  /**
+   * Task D11: Tangenten-Punkte — Berührpunkte der Tangenten vom
+   * refPoint an den Kreis (beide Lösungen, klassische Konstruktion
+   * über rechtwinkliges Dreieck: Winkel = acos(r/d)).
+   */
+  private collectTangent(
+    el: CADElement,
+    wx: number, wy: number,
+    refPoint: { x: number; y: number },
+    tol: number,
+    out: SnapPoint[],
+  ): void {
+    if (el.type !== 'circle' && el.type !== 'arc') return;
+    const r = ((el.properties as Record<string, unknown>).radius as number | undefined) ?? el.width / 2;
+    const dx = refPoint.x - el.x;
+    const dy = refPoint.y - el.y;
+    const d = Math.hypot(dx, dy);
+    // refPoint im Zentrum oder im Kreisinneren: keine reale Tangente
+    if (d <= r) return;
+    const baseAng = Math.atan2(dy, dx);
+    const halfAng = Math.acos(r / d);
+    for (const t of [baseAng + halfAng, baseAng - halfAng]) {
+      const px = el.x + r * Math.cos(t);
+      const py = el.y + r * Math.sin(t);
+      const dist = Math.sqrt((wx - px) ** 2 + (wy - py) ** 2);
+      if (dist < tol) out.push({ x: px, y: py, type: 'tangent' });
+    }
+  }
+
   private collectNearest(el: CADElement, wx: number, wy: number, tol: number, out: SnapPoint[]): void {
     const p = el.properties;
     const check = (x: number, y: number) => {
@@ -400,3 +484,13 @@ export class SnapEngine {
     return { x: snapX, y: snapY, type: 'nearest' };
   }
 }
+
+// ─────────────────────────────────────────────────────────────
+// Task D11: fromOffset — Basispunkt + Eingabefeld dx/dy.
+// Reine Funktion (für from-offset-Snap im UI nutzbar).
+// ─────────────────────────────────────────────────────────────
+
+/** Zielpunkt = Basispunkt + Offsets dx/dy (Task D11 from-offset). */
+export function fromOffset(base: { x: number; y: number }, dx: number, dy: number): { x: number; y: number } {
+  return { x: base.x + dx, y: base.y + dy };
+}