1 files changed, 90 insertions, 0 deletions
diff --git a/src/Text/Def/TextUI/Editor/TextViewExtensions.cs b/src/Text/Def/TextUI/Editor/TextViewExtensions.cs
new file mode 100644
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+++ b/src/Text/Def/TextUI/Editor/TextViewExtensions.cs
@@ -0,0 +1,90 @@
+//
+//  Copyright (c) Microsoft Corporation. All rights reserved.
+//  Licensed under the MIT License. See License.txt in the project root for license information.
+//
+using System;
+
+namespace Microsoft.VisualStudio.Text.Editor
+{
+    /// <summary>
+    /// Utility <see cref="ITextView"/> extension methods.
+    /// </summary>
+    public static class TextViewExtensions
+    {
+        /// <summary>
+        /// Gets whether given <see cref="ITextView"/> is embedded in another <see cref="ITextView"/>.
+        /// </summary>
+        /// <param name="textView">The <see cref="ITextView"/> for which to determine if it's embedded.</param>
+        /// <returns><c>true</c> if given <see cref="ITextView"/> is embedded, <c>false</c> otherwise.</returns>
+        public static bool IsEmbeddedTextView(this ITextView textView)
+        {
+            if (textView == null)
+            {
+                throw new ArgumentNullException(nameof(textView));
+            }
+
+            return textView.Roles.Contains(PredefinedTextViewRoles.EmbeddedPeekTextView);
+        }
+
+        /// <summary>
+        /// Gets containing <see cref="ITextView"/> for given embedded <see cref="ITextView"/>.
+        /// </summary>
+        /// <param name="textView">An embedded <see cref="ITextView"/>, for which to get a containing <see cref="ITextView"/>.</param>
+        /// <param name="containingTextView">A <see cref="ITextView"/> that contains given <see cref="ITextView"/> or null if
+        /// given <see cref="ITextView"/> is not embedded in another <see cref="ITextView"/>.</param>
+        /// <returns><c>true</c> if containing <see cref="ITextView"/> was found, <c>false</c> otherwise.</returns>
+        public static bool TryGetContainingTextView(this ITextView textView, out ITextView containingTextView)
+        {
+            if (textView == null)
+            {
+                throw new ArgumentNullException(nameof(textView));
+            }
+
+            // Extra scrutiny because Peek is on a different layer and we cannot just rely on it doing the right thing
+            if (textView.IsEmbeddedTextView())
+            {
+                bool success = textView.Properties.TryGetProperty("PeekContainingTextView", out containingTextView);
+                if (!success || containingTextView == null)
+                {
+                    throw new InvalidOperationException("Unexpected failure to obtain containing text view of an embedded text view.");
+                }
+
+                return true;
+            }
+
+            containingTextView = null;
+            return false;
+        }
+
+        /// <summary>
+        /// Determines whether a view is in the process of being laid out or is preparing to be laid out.
+        /// </summary>
+        /// <param name="textView">The <see cref="ITextView"/> to check.</param>
+        /// <remarks>
+        /// As opposed to <see cref="ITextView.InLayout"/>, it is safe to get the <see cref="ITextView.TextViewLines"/>
+        /// but attempting to queue another layout will cause a reentrant layout exception.
+        /// </remarks>
+        public static bool GetInOuterLayout(this ITextView textView)
+        {
+            if (textView == null)
+            {
+                throw new ArgumentNullException(nameof(textView));
+            }
+
+            return ((ITextView2)textView).InOuterLayout;
+        }
+
+        /// <summary>
+        /// Gets an object for managing selections within the view.
+        /// </summary>
+        public static IMultiSelectionBroker GetMultiSelectionBroker(this ITextView textView)
+        {
+            if (textView == null)
+            {
+                throw new ArgumentNullException(nameof(textView));
+            }
+
+            return ((ITextView2)textView).MultiSelectionBroker;
+        }
+    }
+}