Add openDocuments property to OakDocumentController

This uses OakDocument’s isOpen property to know which documents are open.

Currently not KVO compliant, but it probably should be.

Frameworks/document/src/OakDocumentController.h

@@ -18,6 +18,7 @@ PUBLIC @interface OakDocumentController : NSObject
 - (OakDocument*)documentWithPath:(NSString*)aPath;
 - (OakDocument*)findDocumentWithIdentifier:(NSUUID*)anUUID;
 - (NSArray<OakDocument*>*)documents;
+- (NSArray<OakDocument*>*)openDocuments;
 
 - (NSInteger)lruRankForDocument:(OakDocument*)aDocument;
 - (void)didTouchDocument:(OakDocument*)aDocument;

Frameworks/document/src/OakDocumentController.mm

@@ -188,6 +188,11 @@ namespace
 	return res;
 }
 
+- (NSArray<OakDocument*>*)openDocuments
+{
+	return [self.documents filteredArrayUsingPredicate:[NSPredicate predicateWithFormat:@"isOpen == YES"]];
+}
+
 // ======================
 // = Last Recently Used =
 // ======================