Add reader-only startup and preview find

MacDown/Code/Application/MPMainController.m

@@ -96,6 +96,15 @@ NS_INLINE void treat()
     }];
 }
 
+NS_INLINE MPDocument *MPDocumentForFindActions()
+{
+    NSWindow *window = NSApp.keyWindow ?: NSApp.mainWindow;
+    id document = window.windowController.document;
+    if ([document isKindOfClass:MPDocument.class])
+        return document;
+
+    return nil;
+}
 
 @interface MPMainController ()
 @property (readonly) NSWindowController *preferencesWindowController;
@@ -216,9 +225,49 @@ - (IBAction)openGitHub:(id)sender
     [[NSWorkspace sharedWorkspace] openURL:url];
 }
 
+- (IBAction)performFindPanelAction:(id)sender
+{
+    MPDocument *document = MPDocumentForFindActions();
+    if (![document respondsToSelector:_cmd])
+    {
+        NSBeep();
+        return;
+    }
+
+    [document performFindPanelAction:sender];
+}
+
+- (IBAction)centerSelectionInVisibleArea:(id)sender
+{
+    MPDocument *document = MPDocumentForFindActions();
+    if (![document respondsToSelector:_cmd])
+    {
+        NSBeep();
+        return;
+    }
+
+    [document centerSelectionInVisibleArea:sender];
+}
+
 
 #pragma mark - Override
 
+- (BOOL)validateUserInterfaceItem:(id<NSValidatedUserInterfaceItem>)item
+{
+    if (item.action == @selector(performFindPanelAction:) ||
+        item.action == @selector(centerSelectionInVisibleArea:))
+    {
+        MPDocument *document = MPDocumentForFindActions();
+        if (![document respondsToSelector:item.action])
+            return NO;
+        if ([document respondsToSelector:@selector(validateUserInterfaceItem:)])
+            return [document validateUserInterfaceItem:item];
+        return YES;
+    }
+
+    return YES;
+}
+
 - (instancetype)init
 {
     self = [super init];

MacDown/Code/Document/MPDocument.h

@@ -19,6 +19,9 @@
 @property (nonatomic, readwrite) NSString *markdown;
 @property (nonatomic, readonly) NSString *html;
 
+- (IBAction)performFindPanelAction:(id)sender;
+- (IBAction)centerSelectionInVisibleArea:(id)sender;
+
 /**
  * Toggle the checkbox at the specified index in the markdown source.
  * Unchecked checkboxes ([ ]) become checked ([x]), and vice versa.