store position in location hash, allowing resharing

packages/client/src/components/CanvasWrapper.tsx

@@ -19,17 +19,65 @@ export const CanvasWrapper = () => {
   );
 };
 
+const parseHashParams = (canvas: Canvas) => {
+  // maybe move this to a utility inside routes.ts
+
+  let { hash } = new URL(window.location.href);
+  if (hash.indexOf("#") === 0) {
+    hash = hash.slice(1);
+  }
+  let params = new URLSearchParams(hash);
+
+  let position: {
+    x?: number;
+    y?: number;
+    zoom?: number;
+  } = {};
+
+  if (params.has("x") && !isNaN(parseInt(params.get("x")!)))
+    position.x = parseInt(params.get("x")!);
+  if (params.has("y") && !isNaN(parseInt(params.get("y")!)))
+    position.y = parseInt(params.get("y")!);
+  if (params.has("zoom") && !isNaN(parseInt(params.get("zoom")!)))
+    position.zoom = parseInt(params.get("zoom")!);
+
+  if (
+    typeof position.x === "number" &&
+    typeof position.y === "number" &&
+    typeof position.zoom === "number"
+  ) {
+    const { transformX, transformY } = canvas.canvasToPanZoomTransform(
+      position.x,
+      position.y
+    );
+
+    return {
+      x: transformX,
+      y: transformY,
+      zoom: position.zoom,
+    };
+  }
+};
+
 const CanvasInner = () => {
   const canvasRef = createRef<HTMLCanvasElement>();
   const { config, setCanvasPosition, setCursorPosition } = useAppContext();
   const PanZoom = useContext(RendererContext);
-  // const { centerView } = useControls();
 
   useEffect(() => {
     if (!config.canvas || !canvasRef.current) return;
     const canvas = canvasRef.current!;
     const canvasInstance = new Canvas(config, canvas, PanZoom);
-    // centerView();
+
+    {
+      // TODO: handle hash changes and move viewport
+      // NOTE: this will need to be cancelled if handleViewportMove was executed recently
+
+      const position = parseHashParams(canvasInstance);
+      if (position) {
+        PanZoom.setPosition(position, { suppressEmit: true });
+      }
+    }
 
     const handleViewportMove = throttle((state: ViewportMoveEvent) => {
       const pos = canvasInstance.panZoomTransformToCanvas();
@@ -45,7 +93,7 @@ const CanvasInner = () => {
       window.location.replace(Routes.canvas(canvasPosition));
     }, 1000);
 
-    const handleCursorPos = (pos: IPosition) => {
+    const handleCursorPos = throttle((pos: IPosition) => {
       if (
         pos.x < 0 ||
         pos.y < 0 ||
@@ -54,9 +102,10 @@ const CanvasInner = () => {
       ) {
         setCursorPosition();
       } else {
-        setCursorPosition(pos);
+        // fixes not passing the current value
+        setCursorPosition({ ...pos });
       }
-    };
+    }, 1);
 
     PanZoom.addListener("viewportMove", handleViewportMove);
     canvasInstance.on("cursorPos", handleCursorPos);
@@ -66,7 +115,9 @@ const CanvasInner = () => {
       PanZoom.removeListener("viewportMove", handleViewportMove);
       canvasInstance.off("cursorPos", handleCursorPos);
     };
-  }, [PanZoom, canvasRef, config, setCanvasPosition]);
+
+    // do not include canvasRef, it causes infinite re-renders
+  }, [PanZoom, config, setCanvasPosition, setCursorPosition]);
 
   return (
     <canvas

packages/client/src/lib/canvas.ts

@@ -158,6 +158,22 @@ export class Canvas extends EventEmitter<CanvasEvents> {
       });
   }
 
+  canvasToPanZoomTransform(x: number, y: number) {
+    let transformX = 0;
+    let transformY = 0;
+
+    if (this.PanZoom.flags.useZoom) {
+      // CSS Zoom does not alter this (obviously)
+      transformX = this.canvas.width / 2 - x;
+      transformY = this.canvas.height / 2 - y;
+    } else {
+      transformX = this.canvas.width / 2 - x;
+      transformY = this.canvas.height / 2 - y;
+    }
+
+    return { transformX, transformY };
+  }
+
   panZoomTransformToCanvas() {
     const { x, y, scale: zoom } = this.PanZoom.transform;
     const rect = this.canvas.getBoundingClientRect();

packages/lib/src/renderer/PanZoom.ts

@@ -82,6 +82,8 @@ interface ISetup {
    * [minimum scale, maximum scale]
    */
   scale: [number, number];
+
+  initialTransform?: TransformState;
 }
 
 // TODO: move these event interfaces out
@@ -106,9 +108,12 @@ interface PanZoomEvents {
   click: (e: ClickEvent) => void;
   hover: (e: HoverEvent) => void;
   viewportMove: (e: ViewportMoveEvent) => void;
+  initialize: () => void;
 }
 
 export class PanZoom extends EventEmitter<PanZoomEvents> {
+  private initialized = false;
+
   public $wrapper: HTMLDivElement = null as any;
   public $zoom: HTMLDivElement = null as any;
   public $move: HTMLDivElement = null as any;
@@ -165,6 +170,53 @@ export class PanZoom extends EventEmitter<PanZoomEvents> {
     this.detectFlags();
     this.registerMouseEvents();
     this.registerTouchEvents();
+
+    this.initialized = true;
+
+    if (this.setup.initialTransform) {
+      // use initial transform if it is set
+      // initialTransform is set from #setPosition() when PanZoom is not initalized
+
+      let { x, y, scale } = this.setup.initialTransform;
+
+      this.transform.x = x;
+      this.transform.y = y;
+      this.transform.scale = scale;
+      this.update({ suppressEmit: true });
+    }
+
+    this.emit("initialize");
+  }
+
+  /**
+   * Sets transform data
+   *
+   * @param position
+   * @param position.x Transform X
+   * @param position.y Transform Y
+   * @param position.zoom Zoom scale
+   * @param flags
+   * @param flags.suppressEmit If true, don't emit a viewport change
+   * @returns
+   */
+  setPosition(
+    { x, y, zoom }: { x: number; y: number; zoom: number },
+    { suppressEmit } = { suppressEmit: false }
+  ) {
+    if (!this.initialized) {
+      // elements are not yet available, store them to be used upon initialization
+      this.setup.initialTransform = {
+        x,
+        y,
+        scale: zoom,
+      };
+      return;
+    }
+
+    this.transform.x = x;
+    this.transform.y = y;
+    this.transform.scale = zoom;
+    this.update({ suppressEmit });
   }
 
   detectFlags() {
@@ -453,12 +505,28 @@ export class PanZoom extends EventEmitter<PanZoomEvents> {
     );
   }
 
-  update() {
+  /**
+   * Update viewport scale and position
+   *
+   * @param flags
+   * @param flags.suppressEmit Do not emit viewportMove
+   */
+  update(
+    {
+      suppressEmit,
+    }: {
+      suppressEmit: boolean;
+    } = {
+      suppressEmit: false,
+    }
+  ) {
+    if (!suppressEmit) {
       this.emit("viewportMove", {
         scale: this.transform.scale,
         x: this.transform.x,
         y: this.transform.y,
       });
+    }
 
     if (this.flags.useZoom) {
       this.$zoom.style.setProperty("zoom", this.transform.scale * 100 + "%");