grid support (1st iteration) (#1788)

Co-authored-by: dwelle <luzar.david@gmail.com>

src/element/dragElements.ts

@@ -0,0 +1,72 @@
+import { NonDeletedExcalidrawElement } from "./types";
+import { getCommonBounds } from "./bounds";
+import { mutateElement } from "./mutateElement";
+import { SHAPES } from "../shapes";
+import { getPerfectElementSize } from "./sizeHelpers";
+
+export const dragSelectedElements = (
+  selectedElements: NonDeletedExcalidrawElement[],
+  pointerX: number,
+  pointerY: number,
+) => {
+  const [x1, y1] = getCommonBounds(selectedElements);
+  selectedElements.forEach((element) => {
+    mutateElement(element, {
+      x: pointerX + element.x - x1,
+      y: pointerY + element.y - y1,
+    });
+  });
+};
+
+export const getDragOffsetXY = (
+  selectedElements: NonDeletedExcalidrawElement[],
+  x: number,
+  y: number,
+): [number, number] => {
+  const [x1, y1] = getCommonBounds(selectedElements);
+  return [x - x1, y - y1];
+};
+
+export const dragNewElement = (
+  draggingElement: NonDeletedExcalidrawElement,
+  elementType: typeof SHAPES[number]["value"],
+  originX: number,
+  originY: number,
+  x: number,
+  y: number,
+  width: number,
+  height: number,
+  isResizeWithSidesSameLength: boolean,
+  isResizeCenterPoint: boolean,
+) => {
+  if (isResizeWithSidesSameLength) {
+    ({ width, height } = getPerfectElementSize(
+      elementType,
+      width,
+      y < originY ? -height : height,
+    ));
+
+    if (height < 0) {
+      height = -height;
+    }
+  }
+
+  let newX = x < originX ? originX - width : originX;
+  let newY = y < originY ? originY - height : originY;
+
+  if (isResizeCenterPoint) {
+    width += width;
+    height += height;
+    newX = originX - width / 2;
+    newY = originY - height / 2;
+  }
+
+  if (width !== 0 && height !== 0) {
+    mutateElement(draggingElement, {
+      x: newX,
+      y: newY,
+      width: width,
+      height: height,
+    });
+  }
+};