Add support for pre-defined zoom/pan settings.

src/components-lib/zoom/zoom-view-context.ts

@@ -0,0 +1,57 @@
+import { ViewContext } from 'view';
+import { ZoomConfig, ZoomDefault } from './types.js';
+import { dispatchViewContextChangeEvent } from '../../view/view.js';
+
+interface ZoomViewContext {
+  // Populate this to request zoom to a particular scale/x/y. An empty object
+  // will reset to default, null will make no change.
+  zoom?: ZoomConfig | null;
+
+  // This will be populated with whether or not the current zoom is at the
+  // default level.
+  isDefault?: boolean;
+}
+
+interface ZoomsViewContext {
+  [targetID: string]: ZoomViewContext;
+}
+
+declare module 'view' {
+  interface ViewContext {
+    zoom?: ZoomsViewContext;
+  }
+}
+
+export const generateViewContextForZoomChange = (
+  targetID: string,
+  options?: {
+    zoom?: ZoomConfig | null;
+    isDefault?: boolean;
+  },
+): ViewContext | null => {
+  return {
+    zoom: {
+      [targetID]: {
+        zoom: options?.zoom ?? null,
+        ...(options?.isDefault !== undefined && { isDefault: options.isDefault }),
+      },
+    },
+  };
+};
+
+/**
+ * Convenience wrapper to convert a zoom default into a dispatched view context
+ * change.
+ */
+export const handleZoomDefaultEvent = (
+  element: EventTarget,
+  ev: CustomEvent<ZoomDefault>,
+  targetID?: string,
+): void => {
+  targetID && dispatchViewContextChangeEvent(
+    element,
+    generateViewContextForZoomChange(targetID, {
+      isDefault: ev.detail.isDefault,
+    }),
+  );
+};