MacPDF: Add a "Go to Page..." menu item

xib changes:
* Add a "Go" toplevel submenu
* Put a "Go to Page..." menu item in it
* Add showGoToPageDialog: to first responder
* Bind action of new menu item to that

The dialog is just a janky NSAlert for now.

Meta/Lagom/Contrib/MacPDF/Base.lproj/MainMenu.xib

@@ -636,6 +636,19 @@
                         </items>
                     </menu>
                 </menuItem>
+                <menuItem title="Go" id="XZ6-XO-pVc">
+                    <modifierMask key="keyEquivalentModifierMask"/>
+                    <menu key="submenu" title="Go" id="u8F-oH-oMu">
+                        <items>
+                            <menuItem title="Go to Page…" keyEquivalent="g" id="Ou1-5M-LzJ">
+                                <modifierMask key="keyEquivalentModifierMask" option="YES" command="YES"/>
+                                <connections>
+                                    <action selector="showGoToPageDialog:" target="-1" id="hmq-Sy-pJC"/>
+                                </connections>
+                            </menuItem>
+                        </items>
+                    </menu>
+                </menuItem>
                 <menuItem title="Window" id="aUF-d1-5bR">
                     <modifierMask key="keyEquivalentModifierMask"/>
                     <menu key="submenu" title="Window" systemMenu="window" id="Td7-aD-5lo">

Meta/Lagom/Contrib/MacPDF/LagomPDFDocument.h

@@ -19,6 +19,8 @@ NS_ASSUME_NONNULL_BEGIN
     IBOutlet LagomPDFView* _pdfView;
 }
 
+- (IBAction)showGoToPageDialog:(id)sender;
+
 @end
 
 NS_ASSUME_NONNULL_END

Meta/Lagom/Contrib/MacPDF/LagomPDFDocument.mm

@@ -142,4 +142,28 @@
     return YES;
 }
 
+- (IBAction)showGoToPageDialog:(id)sender
+{
+    auto alert = [[NSAlert alloc] init];
+    alert.messageText = @"Page Number";
+    [alert addButtonWithTitle:@"Go"];
+    [alert addButtonWithTitle:@"Cancel"];
+
+    // FIXME: Pre-populate with current page.
+    auto textField = [[NSTextField alloc] initWithFrame:NSMakeRect(0, 0, 100, 24)];
+    NSNumberFormatter* formatter = [[NSNumberFormatter alloc] init];
+    formatter.numberStyle = NSNumberFormatterNoStyle; // Integers only.
+    [textField setFormatter:formatter];
+
+    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]];
+                  }];
+}
+
 @end

Meta/Lagom/Contrib/MacPDF/LagomPDFView.h

@@ -20,5 +20,6 @@
 }
 
 - (void)setDocument:(WeakPtr<PDF::Document>)doc;
+- (void)goToPage:(int)page;
 
 @end

Meta/Lagom/Contrib/MacPDF/LagomPDFView.mm

@@ -70,6 +70,20 @@ static NSBitmapImageRep* ns_from_gfx(NonnullRefPtr<Gfx::Bitmap> bitmap_p)
     [self invalidateCachedBitmap];
 }
 
+- (void)goToPage:(int)page
+{
+    if (!_doc)
+        return;
+
+    int new_index = max(0, min(page - 1, _doc->get_page_count() - 1));
+    if (new_index == _page_index)
+        return;
+
+    _page_index = new_index;
+    [self invalidateRestorableState];
+    [self invalidateCachedBitmap];
+}
+
 #pragma mark Drawing
 
 - (void)invalidateCachedBitmap
@@ -113,21 +127,15 @@ static NSBitmapImageRep* ns_from_gfx(NonnullRefPtr<Gfx::Bitmap> bitmap_p)
 // Called on left arrow.
 - (IBAction)moveLeft:(id)sender
 {
-    if (_page_index > 0) {
-        _page_index--;
-        [self invalidateRestorableState];
-        [self invalidateCachedBitmap];
-    }
+    int current_page = _page_index + 1;
+    [self goToPage:current_page - 1];
 }
 
 // Called on right arrow.
 - (IBAction)moveRight:(id)sender
 {
-    if (_page_index < _doc->get_page_count() - 1) {
-        _page_index++;
-        [self invalidateRestorableState];
-        [self invalidateCachedBitmap];
-    }
+    int current_page = _page_index + 1;
+    [self goToPage:current_page + 1];
 }
 
 #pragma mark State restoration