Allow binding linear elements to other elements (#1899)

* Refactor: simplify linear element type

* Refactor: dedupe scrollbar handling

* First step towards binding - establish relationship and basic test for dragged lines

* Refactor: use zoom from appstate

* Refactor: generalize getElementAtPosition

* Only consider bindable elements in hit test

* Refactor: pull out pieces of hit test for reuse later

* Refactor: pull out diamond from hit test for reuse later

* Refactor: pull out text from hit test for reuse later

* Suggest binding when hovering

* Give shapes in regression test real size

* Give shapes in undo/redo test real size

* Keep bound element highlighted

* Show binding suggestion for multi-point elements

* Move binding to its on module with functions so that I can use it from actions, add support for binding end of multi-point elements

* Use Id instead of ID

* Improve boundary offset for non-squarish elements

* Fix localStorage for binding on linear elements

* Simplify dragging code and fix elements bound twice to the same shape

* Fix binding for rectangles

* Bind both ends at the end of the linear element creation, needed for focus points

* wip

* Refactor: Renames and reshapes for next commit

* Calculate and store focus points and gaps, but dont use them yet

* Focus points for rectangles

* Dont blow up when canceling linear element

* Stop suggesting binding when a non-compatible tool is selected

* Clean up collision code

* Using Geometric Algebra for hit tests

* Correct binding for all shapes

* Constant gap around polygon corners

* Fix rotation handling

* Generalize update and fix hit test for rotated elements

* Handle rotation realtime

* Handle scaling

* Remove vibration when moving bound and binding element together

* Handle simultenous scaling

* Allow binding and unbinding when editing linear elements

* Dont delete binding when the end point wasnt touched

* Bind on enter/escape when editing

* Support multiple suggested bindable elements in preparation for supporting linear elements dragging

* Update binding when moving linear elements

* Update binding when resizing linear elements

* Dont re-render UI on binding hints

* Update both ends when one is moved

* Use distance instead of focus point for binding

* Complicated approach for posterity, ignore this commit

* Revert the complicated approach

* Better focus point strategy, working for all shapes

* Update snapshots

* Dont break binding gap when mirroring shape

* Dont break binding gap when grid mode pushes it inside

* Dont bind draw elements

* Support alt duplication

* Fix alt duplication to

* Support cmd+D duplication

* All copy mechanisms are supported

* Allow binding shapes to arrows, having arrows created first

* Prevent arrows from disappearing for ellipses

* Better binding suggestion highlight for shapes

* Dont suggest second binding for simple elements when editing or moving them

* Dont steal already bound linear elements when moving shapes

* Fix highlighting diamonds and more precisely highlight other shapes

* Highlight linear element edges for binding

* Highlight text binding too

* Handle deletion

* Dont suggest second binding for simple linear elements when creating them

* Dont highlight bound element during creation

* Fix binding for rotated linear elements

* Fix collision check for ellipses

* Dont show suggested bindings for selected pairs

* Bind multi-point linear elements when the tool is switched - important for mobile

* Handle unbinding one of two bound edges correctly

* Rename boundElement in state to startBoundElement

* Dont double account for zoom when rendering binding highlight

* Fix rendering of edited linear element point handles

* Suggest binding when adding new point to a linear element

* Bind when adding a new point to a linear element and dont unbind when moving middle elements

* Handle deleting points

* Add cmd modifier key to disable binding

* Use state for enabling binding, fix not binding for linear elements during creation

* Drop support for binding lines, only arrows are bindable

* Reset binding mode on blur

* Fix not binding lines

src/element/handlerRectangles.ts

@@ -1,10 +1,14 @@
 import { ExcalidrawElement, PointerType } from "./types";
 
-import { getElementAbsoluteCoords } from "./bounds";
+import { getElementAbsoluteCoords, Bounds } from "./bounds";
 import { rotate } from "../math";
 
 type Sides = "n" | "s" | "w" | "e" | "nw" | "ne" | "sw" | "se" | "rotation";
 
+export type Handlers = Partial<
+  { [T in Sides]: [number, number, number, number] }
+>;
+
 const handleSizes: { [k in PointerType]: number } = {
   mouse: 8,
   pen: 16,
@@ -61,12 +65,12 @@ const generateHandler = (
 };
 
 export const handlerRectanglesFromCoords = (
-  [x1, y1, x2, y2]: [number, number, number, number],
+  [x1, y1, x2, y2]: Bounds,
   angle: number,
   zoom: number,
   pointerType: PointerType = "mouse",
   omitSides: { [T in Sides]?: boolean } = {},
-): Partial<{ [T in Sides]: [number, number, number, number] }> => {
+): Handlers => {
   const size = handleSizes[pointerType];
   const handlerWidth = size / zoom;
   const handlerHeight = size / zoom;