1 files changed, 59 insertions, 0 deletions
diff --git a/sdc-workflow-designer-ui/src/app/paletx/core/overlay/scroll/reposition-scroll-strategy.ts b/sdc-workflow-designer-ui/src/app/paletx/core/overlay/scroll/reposition-scroll-strategy.ts
new file mode 100644
index 00000000..b15d5dea
--- /dev/null
+++ b/sdc-workflow-designer-ui/src/app/paletx/core/overlay/scroll/reposition-scroll-strategy.ts
@@ -0,0 +1,59 @@
+/**
+ * @license
+ * Copyright Google Inc. All Rights Reserved.
+ *
+ * Use of this source code is governed by an MIT-style license that can be
+ * found in the LICENSE file at https://angular.io/license
+ */
+/* tslint:disable:array-type member-access variable-name typedef
+ only-arrow-functions directive-class-suffix component-class-suffix
+ component-selector*/
+import {Subscription} from 'rxjs/Subscription';
+
+import {OverlayRef} from '../overlay-ref';
+
+import {ScrollDispatcher} from './scroll-dispatcher';
+import {getMdScrollStrategyAlreadyAttachedError, ScrollStrategy} from './scroll-strategy';
+
+/**
+ * Config options for the RepositionScrollStrategy.
+ */
+export interface RepositionScrollStrategyConfig { scrollThrottle?: number; }
+
+/**
+ * Strategy that will update the element position as the user is scrolling.
+ */
+export class RepositionScrollStrategy implements ScrollStrategy {
+  private _scrollSubscription: Subscription|null = null;
+  private _overlayRef: OverlayRef;
+
+  constructor(
+		private _scrollDispatcher: ScrollDispatcher,
+		private _config?: RepositionScrollStrategyConfig) {}
+
+  attach(overlayRef: OverlayRef) {
+	if (this._overlayRef) {
+		throw getMdScrollStrategyAlreadyAttachedError();
+	}
+
+	this._overlayRef = overlayRef;
+  }
+
+  enable() {
+	if (!this._scrollSubscription) {
+		const throttle = this._config ? this._config.scrollThrottle : 0;
+
+		this._scrollSubscription =
+			this._scrollDispatcher.scrolled(throttle, () => {
+			this._overlayRef.updatePosition();
+			});
+	}
+  }
+
+  disable() {
+	if (this._scrollSubscription) {
+		this._scrollSubscription.unsubscribe();
+		this._scrollSubscription = null;
+	}
+  }
+}