1 files changed, 77 insertions, 0 deletions
diff --git a/sdc-workflow-designer-ui/src/app/paletx/core/overlay/scroll/block-scroll-strategy.ts b/sdc-workflow-designer-ui/src/app/paletx/core/overlay/scroll/block-scroll-strategy.ts
new file mode 100644
index 00000000..d1c1d401
--- /dev/null
+++ b/sdc-workflow-designer-ui/src/app/paletx/core/overlay/scroll/block-scroll-strategy.ts
@@ -0,0 +1,77 @@
+/**
+ * @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 {ViewportRuler} from '../position/viewport-ruler';
+
+import {ScrollStrategy} from './scroll-strategy';
+
+/**
+ * Strategy that will prevent the user from scrolling while the overlay is
+ * visible.
+ */
+export class BlockScrollStrategy implements ScrollStrategy {
+  private _previousHTMLStyles = {top: '', left: ''};
+  private _previousScrollPosition: {top: number, left: number};
+  private _isEnabled = false;
+
+  constructor(private _viewportRuler: ViewportRuler) {}
+
+  attach() {
+    //
+  }
+
+  enable() {
+	if (this._canBeEnabled()) {
+		const root = document.documentElement;
+
+		this._previousScrollPosition =
+			this._viewportRuler.getViewportScrollPosition();
+
+      // Cache the previous inline styles in case the user had set them.
+		this._previousHTMLStyles.left = root.style.left || '';
+		this._previousHTMLStyles.top = root.style.top || '';
+
+      // Note: we're using the `html` node, instead of the `body`, because the
+      // `body` may have the user agent margin, whereas the `html` is guaranteed
+      // not to have one.
+		root.style.left = `${- this._previousScrollPosition.left}px`;
+		root.style.top = `${- this._previousScrollPosition.top}px`;
+		root.classList.add('cdk-global-scrollblock');
+		this._isEnabled = true;
+	}
+  }
+
+  disable() {
+	if (this._isEnabled) {
+		this._isEnabled = false;
+		document.documentElement.style.left = this._previousHTMLStyles.left;
+		document.documentElement.style.top = this._previousHTMLStyles.top;
+		document.documentElement.classList.remove('cdk-global-scrollblock');
+		window.scroll(
+			this._previousScrollPosition.left, this._previousScrollPosition.top);
+	}
+  }
+
+  private _canBeEnabled(): boolean {
+    // Since the scroll strategies can't be singletons, we have to use a global
+    // CSS class
+    // (`cdk-global-scrollblock`) to make sure that we don't try to disable
+    // global scrolling multiple times.
+	if (document.documentElement.classList.contains('cdk-global-scrollblock') ||
+		this._isEnabled) {
+		return false;
+	}
+
+	const body = document.body;
+	const viewport = this._viewportRuler.getViewportRect();
+	return body.scrollHeight > viewport.height ||
+		body.scrollWidth > viewport.width;
+  }
+}