MacPDF: Make opt-up and opt-down always go to previous / next page

When the outline has focus, arrow keys navigate the outline instead
of changing the current page.

Add opt-up and opt-down as a way to move by one page even when the
outline has focus. (This matches Preview.app.)

xib change: Added two menu Previous Page with key equivalent opt-up
and Next Page with key equivalent opt-down to Go menu and bound them to
goToPreviousPage: and goToNextPage: on First Responder.

When the outline has focus, the responder chain is outline ->
window, so also add the actions on the window controller, and
let that forward to the PDF view.

Meta/Lagom/Contrib/MacPDF/MacPDFView.h

@@ -23,4 +23,7 @@
 
 - (void)setDelegate:(id<MacPDFViewDelegate>)delegate;
 
+- (IBAction)goToNextPage:(id)sender;
+- (IBAction)goToPreviousPage:(id)sender;
+
 @end

Meta/Lagom/Contrib/MacPDF/MacPDFView.mm

@@ -146,6 +146,18 @@ static NSBitmapImageRep* ns_from_gfx(NonnullRefPtr<Gfx::Bitmap> bitmap_p)
     return YES;
 }
 
+- (IBAction)goToNextPage:(id)sender
+{
+    int current_page = _page_index + 1;
+    [self goToPage:current_page + 1];
+}
+
+- (IBAction)goToPreviousPage:(id)sender
+{
+    int current_page = _page_index + 1;
+    [self goToPage:current_page - 1];
+}
+
 - (void)keyDown:(NSEvent*)event
 {
     // Calls moveLeft: or moveRight: below.
@@ -155,15 +167,13 @@ static NSBitmapImageRep* ns_from_gfx(NonnullRefPtr<Gfx::Bitmap> bitmap_p)
 // Called on left arrow.
 - (IBAction)moveLeft:(id)sender
 {
-    int current_page = _page_index + 1;
-    [self goToPage:current_page - 1];
+    [self goToPreviousPage:self];
 }
 
 // Called on right arrow.
 - (IBAction)moveRight:(id)sender
 {
-    int current_page = _page_index + 1;
-    [self goToPage:current_page + 1];
+    [self goToNextPage:self];
 }
 
 #pragma mark - State restoration

Meta/Lagom/Contrib/MacPDF/MacPDFWindowController.h

@@ -18,7 +18,11 @@ NS_ASSUME_NONNULL_BEGIN
 @interface MacPDFWindowController : NSWindowController <MacPDFViewDelegate, NSOutlineViewDelegate, NSToolbarDelegate>
 
 - (instancetype)initWithDocument:(MacPDFDocument*)document;
+
+- (IBAction)goToNextPage:(id)sender;
+- (IBAction)goToPreviousPage:(id)sender;
 - (IBAction)showGoToPageDialog:(id)sender;
+
 - (void)pdfDidInitialize;
 
 @end

Meta/Lagom/Contrib/MacPDF/MacPDFWindowController.mm

@@ -122,6 +122,16 @@
     _outlineView.delegate = self;
 }
 
+- (IBAction)goToNextPage:(id)sender
+{
+    [_pdfView goToNextPage:sender];
+}
+
+- (IBAction)goToPreviousPage:(id)sender
+{
+    [_pdfView goToPreviousPage:sender];
+}
+
 - (IBAction)showGoToPageDialog:(id)sender
 {
     auto alert = [[NSAlert alloc] init];

Meta/Lagom/Contrib/MacPDF/MainMenu.xib

@@ -639,10 +639,22 @@
                     <modifierMask key="keyEquivalentModifierMask"/>
                     <menu key="submenu" title="Go" id="u8F-oH-oMu">
                         <items>
-                            <menuItem title="Go to Page…" keyEquivalent="g" id="Ou1-5M-LzJ">
+                            <menuItem title="Previous Page" keyEquivalent="" id="Ou1-5M-LzJ">
+                                <modifierMask key="keyEquivalentModifierMask" option="YES"/>
+                                <connections>
+                                    <action selector="goToPreviousPage:" target="-1" id="e1c-zc-WR6"/>
+                                </connections>
+                            </menuItem>
+                            <menuItem title="Next Page" keyEquivalent="" id="mfm-mG-pLT">
+                                <modifierMask key="keyEquivalentModifierMask" option="YES"/>
+                                <connections>
+                                    <action selector="goToNextPage:" target="-1" id="lt2-m9-Iyp"/>
+                                </connections>
+                            </menuItem>
+                            <menuItem title="Go to Page…" keyEquivalent="g" id="pzP-g1-BeT">
                                 <modifierMask key="keyEquivalentModifierMask" option="YES" command="YES"/>
                                 <connections>
-                                    <action selector="showGoToPageDialog:" target="-1" id="hmq-Sy-pJC"/>
+                                    <action selector="showGoToPageDialog:" target="-1" id="fPI-BN-18g"/>
                                 </connections>
                             </menuItem>
                         </items>