MacPDF: Start moving window-related things into MacPDFWindowController

- MacPDFWindowController is now the xib file's owner
- _pdfView moves over
- MacPDFWindowController is now the MacPDFViewDelegate and responsible
  for updating the window's title
- Due to MacPDFWindowController now being the xib file's owner,
  windowControllerDidLoadNib: is no longer called automatically,
  so call a custom windowIsReady method manually instead

No behavior change.

Meta/Lagom/Contrib/MacPDF/MacPDFWindowController.mm

@@ -6,6 +6,15 @@
 
 #import "MacPDFWindowController.h"
 
+#import "MacPDFDocument.h"
+
+@interface MacPDFWindowController ()
+{
+    MacPDFDocument* _pdfDocument;
+    IBOutlet MacPDFView* _pdfView;
+}
+@end
+
 @implementation MacPDFWindowController
 
 - (instancetype)initWithDocument:(MacPDFDocument*)document
@@ -13,8 +22,53 @@
     if (self = [super initWithWindowNibName:@"MacPDFDocument" owner:self]; !self)
         return nil;
 
+    _pdfDocument = document;
     return self;
 }
 
+- (void)windowDidLoad
+{
+    [super windowDidLoad];
+    [_pdfView setDelegate:self];
+    [_pdfDocument windowIsReady];
+}
+
+- (void)pdfDidInitialize
+{
+    [_pdfView setDocument:_pdfDocument.pdf->make_weak_ptr()];
+    [self pageChanged];
+}
+
+- (IBAction)showGoToPageDialog:(id)sender
+{
+    auto alert = [[NSAlert alloc] init];
+    alert.messageText = @"Page Number";
+    [alert addButtonWithTitle:@"Go"];
+    [alert addButtonWithTitle:@"Cancel"];
+
+    auto textField = [[NSTextField alloc] initWithFrame:NSMakeRect(0, 0, 100, 24)];
+    NSNumberFormatter* formatter = [[NSNumberFormatter alloc] init];
+    formatter.numberStyle = NSNumberFormatterNoStyle; // Integers only.
+    [textField setFormatter:formatter];
+    [textField setIntValue:[_pdfView page]];
+
+    alert.accessoryView = textField;
+    alert.window.initialFirstResponder = textField;
+
+    NSWindow* window = _pdfView.window;
+    [alert beginSheetModalForWindow:window
+                  completionHandler:^(NSModalResponse response) {
+                      if (response == NSAlertFirstButtonReturn)
+                          [self->_pdfView goToPage:[textField intValue]];
+                  }];
+}
+
+#pragma mark - MacPDFViewDelegate
+
+- (void)pageChanged
+{
+    [_pdfView.window setSubtitle:
+                     [NSString stringWithFormat:@"Page %d of %d", [_pdfView page], _pdfDocument.pdf->get_page_count()]];
+}
 
 @end