Add UndeferHandler to invoke a callback once the leaf is ready

Author: kotaindah55

src/utils/UndeferHandler.ts

@@ -0,0 +1,53 @@
+import { App, Component, Plugin, View, WorkspaceLeaf } from 'obsidian';
+
+export class UndeferHandler extends Component {
+    app: App;
+    leaf: WorkspaceLeaf;
+    view: View;
+    callback?: (leaf: WorkspaceLeaf) => unknown;
+
+    constructor(leaf: WorkspaceLeaf, callback: (leaf: WorkspaceLeaf) => unknown) {
+        super();
+        this.app = leaf.app;
+        this.leaf = leaf;
+        this.view = leaf.view;
+        this.callback = callback;
+
+        this.view.addChild(this);
+    }
+
+    onload(): void {
+        // Run the callback immediately if the leaf is not deferred
+        if (!this.leaf.isDeferred) {
+            this.view.removeChild(this);
+            return;
+        }
+
+        // Detach the handler once the plugin has been disabled/unistalled
+        this.registerEvent(this.app.workspace.on(`custom-sort:plugin-unload`, () => this.detach()));
+    }
+
+    onunload(): void {
+        if (this.callback) this.runCallback();
+    }
+
+    // Detach the handler without invoking the callback
+    detach(): void {
+        delete this.callback;
+        this.view.removeChild(this);
+    }
+
+    private async runCallback(): Promise<void> {
+        // Run the callback after the actual view has been loaded
+        await sleep(0);
+        // Do not run the callback if the deferred view was unloaded
+        // because of being closed
+        if (
+            !this.leaf.isDeferred &&
+            this.leaf.parent &&
+            this.leaf.view.getViewType() !== 'empty'
+        ) {
+            this.callback?.(this.leaf);
+        }
+    }
+}