Snap everything to grid (#315)

* Implement snap to grid

- Moves positioning logic to LGraph
- Simplifies code
- Adds Pointer API to alt-clone node
- Removes always_round_positions, replaced by always snap to grid (default size is 1 when always snapping)

Fix refator error

* Fix group items snapped without group

* Allow snapping of all items

- Add snapToGrid to Positionable
- Impl. on all types
- Deprecated: alignToGrid is now a wrapper

* Fix test import alias, update expectations

* Prevent desync of before / after change events

Adds ability to perform late binding of finally() during drag start.

* nit - Refactor

* Fix unwanted snap on node/group add

* nit - Doc

* Add shift key state tracking for snap to grid

Private impl., no state API as yet.

* Add snap guides rendering

Nodes, reroutes

* Optimisation - reroute rendering

 Fixes exponential redraw

* Add snap guidelines for groups

src/Reroute.ts

@@ -73,6 +73,9 @@ export class Reroute implements Positionable, LinkSegment, Serialisable<Serialis
     /** @inheritdoc */
     _pos: Float32Array = this.#malloc.subarray(6, 8)
 
+    /** Colour of the first link that rendered this reroute */
+    _colour?: CanvasColour
+
     /**
      * Used to ensure reroute angles are only executed once per frame. 
      * @todo Calculate on change instead.
@@ -188,6 +191,16 @@ export class Reroute implements Positionable, LinkSegment, Serialisable<Serialis
         this.#pos[1] += deltaY
     }
 
+    /** @inheritdoc */
+    snapToGrid(snapTo: number): boolean {
+        if (!snapTo) return false
+
+        const { pos } = this
+        pos[0] = snapTo * Math.round(pos[0] / snapTo)
+        pos[1] = snapTo * Math.round(pos[1] / snapTo)
+        return true
+    }
+
     calculateAngle(lastRenderTime: number, network: LinkNetwork, linkStart: Point): void {
         // Ensure we run once per render
         if (!(lastRenderTime > this.#lastRenderTime)) return
@@ -241,9 +254,9 @@ export class Reroute implements Positionable, LinkSegment, Serialisable<Serialis
      * 
      * @remarks Leaves {@link ctx}.fillStyle, strokeStyle, and lineWidth dirty (perf.).
      */
-    draw(ctx: CanvasRenderingContext2D, colour: CanvasColour): void {
+    draw(ctx: CanvasRenderingContext2D): void {
         const { pos } = this
-        ctx.fillStyle = colour
+        ctx.fillStyle = this._colour
         ctx.beginPath()
         ctx.arc(pos[0], pos[1], Reroute.radius, 0, 2 * Math.PI)
         ctx.fill()