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/actions/actionFinalize.tsx

@@ -9,15 +9,32 @@ import { register } from "./register";
 import { mutateElement } from "../element/mutateElement";
 import { isPathALoop } from "../math";
 import { LinearElementEditor } from "../element/linearElementEditor";
+import Scene from "../scene/Scene";
+import {
+  maybeBindLinearElement,
+  bindOrUnbindLinearElement,
+} from "../element/binding";
+import { isBindingElement } from "../element/typeChecks";
 
 export const actionFinalize = register({
   name: "finalize",
   perform: (elements, appState) => {
     if (appState.editingLinearElement) {
-      const { elementId } = appState.editingLinearElement;
+      const {
+        elementId,
+        startBindingElement,
+        endBindingElement,
+      } = appState.editingLinearElement;
       const element = LinearElementEditor.getElement(elementId);
 
       if (element) {
+        if (isBindingElement(element)) {
+          bindOrUnbindLinearElement(
+            element,
+            startBindingElement,
+            endBindingElement,
+          );
+        }
         return {
           elements:
             element.points.length < 2 || isInvisiblySmallElement(element)
@@ -66,11 +83,12 @@ export const actionFinalize = register({
       // If the multi point line closes the loop,
       // set the last point to first point.
       // This ensures that loop remains closed at different scales.
+      const isLoop = isPathALoop(multiPointElement.points);
       if (
         multiPointElement.type === "line" ||
         multiPointElement.type === "draw"
       ) {
-        if (isPathALoop(multiPointElement.points)) {
+        if (isLoop) {
           const linePoints = multiPointElement.points;
           const firstPoint = linePoints[0];
           mutateElement(multiPointElement, {
@@ -83,6 +101,23 @@ export const actionFinalize = register({
         }
       }
 
+      if (
+        isBindingElement(multiPointElement) &&
+        !isLoop &&
+        multiPointElement.points.length > 1
+      ) {
+        const [x, y] = LinearElementEditor.getPointAtIndexGlobalCoordinates(
+          multiPointElement,
+          -1,
+        );
+        maybeBindLinearElement(
+          multiPointElement,
+          appState,
+          Scene.getScene(multiPointElement)!,
+          { x, y },
+        );
+      }
+
       if (!appState.elementLocked) {
         appState.selectedElementIds[multiPointElement.id] = true;
       }
@@ -101,6 +136,8 @@ export const actionFinalize = register({
         draggingElement: null,
         multiElement: null,
         editingElement: null,
+        startBoundElement: null,
+        suggestedBindings: [],
         selectedElementIds:
           multiPointElement && !appState.elementLocked
             ? {