Fix drag multiple elements bug (#2023)

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

src/scene/comparisons.ts

@@ -34,6 +34,8 @@ export const getElementAtPosition = (
 ) => {
   let hitElement = null;
   // We need to to hit testing from front (end of the array) to back (beginning of the array)
+  // because array is ordered from lower z-index to highest and we want element z-index
+  // with higher z-index
   for (let i = elements.length - 1; i >= 0; --i) {
     const element = elements[i];
     if (element.isDeleted) {
@@ -48,6 +50,17 @@ export const getElementAtPosition = (
   return hitElement;
 };
 
+export const getElementsAtPosition = (
+  elements: readonly NonDeletedExcalidrawElement[],
+  isAtPositionFn: (element: NonDeletedExcalidrawElement) => boolean,
+) => {
+  // The parameter elements comes ordered from lower z-index to higher.
+  // We want to preserve that order on the returned array.
+  return elements.filter(
+    (element) => !element.isDeleted && isAtPositionFn(element),
+  );
+};
+
 export const getElementContainingPosition = (
   elements: readonly ExcalidrawElement[],
   x: number,

src/scene/index.ts

@@ -14,5 +14,6 @@ export {
   getElementAtPosition,
   getElementContainingPosition,
   hasText,
+  getElementsAtPosition,
 } from "./comparisons";
 export { getZoomOrigin, getNormalizedZoom } from "./zoom";