[quicklook] Update up to beta 4 (#2374)

src/quicklook.cs

@@ -143,6 +143,53 @@ namespace XamCore.QuickLook {
 		[Export ("previewItemTitle")]
 		string ItemTitle { get; }
 	}
+
+	[iOS (11,0)]
+	[Protocol]
+	interface QLPreviewingController {
+		[Export ("preparePreviewOfSearchableItemWithIdentifier:queryString:completionHandler:")]
+		void PreparePreviewOfSearchableItem (string identifier, [NullAllowed] string queryString, Action<NSError> handler);
+
+		[Export ("preparePreviewOfFileAtURL:completionHandler:")]
+		void PreparePreviewOfFile (NSUrl url, Action<NSError> handler);
+	}
+
+	[iOS (11,0)]
+	[BaseType (typeof (NSObject))]
+	interface QLThumbnailProvider {
+		[Export ("provideThumbnailForFileRequest:completionHandler:")]
+		void ProvideThumbnail (QLFileThumbnailRequest request, Action<QLThumbnailReply, NSError> handler);
+	}
+
+	[iOS (11,0)]
+	[BaseType (typeof (NSObject))]
+	[DisableDefaultCtor]
+	interface QLThumbnailReply {
+		[Static]
+		[Export ("replyWithContextSize:drawingBlock:")]
+		QLThumbnailReply CreateReply (CGSize contextSize, Func<CGContext, bool> drawingBlock);
+
+		[Static]
+		[Export ("replyWithContextSize:currentContextDrawingBlock:")]
+		QLThumbnailReply CreateReply (CGSize contextSize, Func<bool> drawingBlock);
+
+		[Static]
+		[Export ("replyWithImageFileURL:")]
+		QLThumbnailReply CreateReply (NSUrl fileUrl);
+	}
+
+	[iOS (11,0)]
+	[BaseType (typeof (NSObject))]
+	interface QLFileThumbnailRequest {
+		[Export ("maximumSize")]
+		CGSize MaximumSize { get; }
+
+		[Export ("scale")]
+		nfloat Scale { get; }
+
+		[Export ("fileURL", ArgumentSemantic.Copy)]
+		NSUrl FileUrl { get; }
+	}
 #else
 	[Static]
 	interface QLThumbnailImage {