QPolygon isValid 추가

src/components/fabric/QPolygon.js

@@ -199,6 +199,32 @@ export default class QPolygon extends fabric.Group {
     this.canvas.renderAll()
   }
 
+  /**
+   * this.lines의 direction이 top 인 line의 모든 합이 bottom 인 line의 모든 합과 같은지 확인
+   * this.lines의 direction이 left 인 line의 모든 합이 right 인 line의 모든 합과 같은지 확인
+   * return {boolean}
+   */
+  isValid() {
+    const leftLinesLengthSum = this.lines
+      .filter((line) => line.direction === 'left')
+      .reduce((sum, line) => sum + line.length, 0)
+    const rightLinesLengthSum = this.lines
+      .filter((line) => line.direction === 'right')
+      .reduce((sum, line) => sum + line.length, 0)
+
+    const topLinesLengthSum = this.lines
+      .filter((line) => line.direction === 'top')
+      .reduce((sum, line) => sum + line.length, 0)
+    const bottomLinesLengthSum = this.lines
+      .filter((line) => line.direction === 'bottom')
+      .reduce((sum, line) => sum + line.length, 0)
+
+    return (
+      leftLinesLengthSum === rightLinesLengthSum &&
+      topLinesLengthSum === bottomLinesLengthSum
+    )
+  }
+
   inPolygon(point) {
     const vertices = this.getCurrentPoints()
     let intersects = 0
@@ -302,6 +328,10 @@ export default class QPolygon extends fabric.Group {
 
   // 보조선 그리기 사각형에서만
   drawHelpLine(chon = 4) {
+    if (!this.isValid()) {
+      return
+    }
+
     if (this.lines.length === 4) {
       this.#drawHelpLineInRect(chon)
     } else if (this.lines.length === 6) {