draw: constrain object move with Shift

Issue #7933

Signed-off-by: Hubert Figuière <[email protected]>
Change-Id: Ie39c15a8552276bc5919ffbbd5dd859695048b9c

browser/src/layer/vector/Path.Drag.js

@@ -198,6 +198,54 @@ L.Handler.PathDrag = L.Handler.extend(/** @lends  L.Path.Drag.prototype */ {
 				x = this._startPoint.x + dx;
 				y = this._startPoint.y + dy;
 			}
+		} if (evt.shiftKey) {
+			var angleOf = function (x, y) {
+				var angle;
+				if (x != 0) {
+					angle = Math.atan(y / Math.abs(x));
+				} else if (y > 0) {
+					angle = Math.PI / 2;
+				} else {
+					angle = - Math.PI / 2;
+				}
+				if (x < 0) {
+					angle = Math.PI - angle;
+				}
+				return angle;
+			};
+			/* Near mean within +/- PI / 8 since we do diagonals */
+			var angleNear = function (angle, near) {
+				return Math.abs(near - angle) < (Math.PI / 8);
+			};
+
+			var dsx = x - this._dragStartPoint.x;
+			var dsy = y - this._dragStartPoint.y;
+			var angle = angleOf(dsx, dsy);
+			console.log('Drag started: Shift is on', this._dragStartPoint.x, this._dragStartPoint.y);
+			console.log('Drag: Shift is on', dsx, dsy, angle / (Math.PI / 180));
+			if (angleNear(angle, 0) || angleNear(angle, Math.PI)) {
+				dy = -this._matrix[5];
+				y = this._startPoint.y;
+			} else if (angleNear(angle, Math.PI / 2) || angleNear(angle, -Math.PI / 2)) {
+				dx = -this._matrix[4];
+				x = this._startPoint.x;
+			} else {
+				console.log('neither');
+				var delta = (Math.abs(dsx) + Math.abs(dsy)) / 2;
+				if (angleNear(angle, Math.PI / 4)) {
+					dx = -this._matrix[4] + delta;
+					dy = -this._matrix[5] + delta;
+				} else if (angleNear(angle, -Math.PI / 4)) {
+					dx = -this._matrix[4] + delta;
+					dy = -this._matrix[5] - delta;
+				} else if (angleNear(angle, Math.PI * 0.75)) {
+					dx = -this._matrix[4] - delta;
+					dy = -this._matrix[5] + delta;
+				} else if (angleNear(angle, -Math.PI * 0.75)) {
+					dx = -this._matrix[4] - delta;
+					dy = -this._matrix[5] - delta;
+				}
+			}
 		}
 
 		// Send events only if point was moved