Add support for page up and page down

src/keys.hh

@@ -16,7 +16,7 @@ struct Key
         Alt     = 2,
         ControlAlt = 3
     };
-    enum NamedKeys : Character
+    enum NamedKey : Character
     {
         Backspace = 256,
         Escape,
@@ -24,6 +24,8 @@ struct Key
         Down,
         Left,
         Right,
+        PageUp,
+        PageDown,
     };
 
     Modifiers modifiers;

src/main.cc

@@ -236,6 +236,31 @@ void do_select_object(Context& context)
     });
 }
 
+template<Key::NamedKey key>
+void do_scroll(Context& context)
+{
+    static_assert(key == Key::PageUp or key == Key::PageDown,
+                  "do_scrool only implements PageUp and PageDown");
+    Window& window = context.window();
+    Buffer& buffer = context.buffer();
+    BufferCoord position = window.position();
+    BufferIterator cursor_pos;
+
+    if (key == Key::PageUp)
+    {
+        position.line -= (window.dimensions().line - 2);
+        cursor_pos = buffer.iterator_at(position);
+    }
+    else if (key == Key::PageDown)
+    {
+        position.line += (window.dimensions().line - 2);
+        cursor_pos = buffer.iterator_at(position + BufferCoord{window.dimensions().line - 1, 0});
+    }
+
+    window.select(cursor_pos);
+    window.set_position(position);
+}
+
 template<typename T>
 class Repeated
 {
@@ -370,6 +395,9 @@ std::unordered_map<Key, std::function<void (Context& context)>> keymap =
     { { Key::Modifiers::Alt, 'x' }, [](Context& context) { context.editor().select(select_whole_lines); } },
 
     { { Key::Modifiers::Alt, 'c' }, [](Context& context) { if (context.has_window()) context.window().center_selection(); } },
+
+    { { Key::Modifiers::None, Key::PageUp }, do_scroll<Key::PageUp> },
+    { { Key::Modifiers::None, Key::PageDown }, do_scroll<Key::PageDown> },
 };
 
 }

src/ncurses.cc

@@ -187,6 +187,8 @@ Key NCursesClient::get_key()
     case KEY_DOWN: return Key::Down;
     case KEY_LEFT: return Key::Left;
     case KEY_RIGHT: return Key::Right;
+    case KEY_PPAGE: return Key::PageUp;
+    case KEY_NPAGE: return Key::PageDown;
     }
     return c;
 }

src/window.hh

@@ -25,7 +25,9 @@ public:
     ~Window();
 
     const BufferCoord& position() const { return m_position; }
+    void set_position(const BufferCoord& position) { m_position = buffer().clamp(position); }
 
+    const DisplayCoord& dimensions() const { return m_dimensions; }
     void set_dimensions(const DisplayCoord& dimensions);
 
     const DisplayBuffer& display_buffer() const { return m_display_buffer; }