LibGUI+WindowServer: Add support for per-GWidget context menus.

You can now simply assign a GMenu as a GWidget's context menu and it will
automagically pop up on right click. :^)

LibGUI/GMenu.cpp

@@ -39,6 +39,17 @@ void GMenu::add_separator()
     m_items.append(make<GMenuItem>(m_menu_id, GMenuItem::Separator));
 }
 
+void GMenu::popup(const Point& screen_position)
+{
+    if (!m_menu_id)
+        realize_menu();
+    WSAPI_ClientMessage request;
+    request.type = WSAPI_ClientMessage::Type::PopupMenu;
+    request.menu.menu_id = m_menu_id;
+    request.menu.position = screen_position;
+    GEventLoop::post_message_to_server(request);
+}
+
 int GMenu::realize_menu()
 {
     WSAPI_ClientMessage request;

LibGUI/GMenu.h

@@ -5,6 +5,7 @@
 #include <AK/Vector.h>
 
 class GAction;
+class Point;
 
 class GMenu {
 public:
@@ -18,6 +19,8 @@ public:
     void add_action(Retained<GAction>&&);
     void add_separator();
 
+    void popup(const Point& screen_position);
+
     Function<void(unsigned)> on_item_activation;
 
 private:

LibGUI/GWidget.cpp

@@ -7,7 +7,7 @@
 #include <SharedGraphics/GraphicsBitmap.h>
 #include <LibGUI/GPainter.h>
 #include <LibGUI/GApplication.h>
-
+#include <LibGUI/GMenu.h>
 #include <unistd.h>
 
 GWidget::GWidget(GWidget* parent)
@@ -161,12 +161,14 @@ void GWidget::handle_mouseup_event(GMouseEvent& event)
         return;
     // It's a click.. but is it a doubleclick?
     // FIXME: This needs improvement.
-    int elapsed_since_last_click = m_click_clock.elapsed();
-    dbgprintf("Click clock elapsed: %d\n", m_click_clock.elapsed());
-    if (elapsed_since_last_click < 250) {
-        doubleclick_event(event);
-    } else {
-        m_click_clock.start();
+    if (m_click_clock.is_valid()) {
+        int elapsed_since_last_click = m_click_clock.elapsed();
+        dbgprintf("Click clock elapsed: %d\n", m_click_clock.elapsed());
+        if (elapsed_since_last_click < 250) {
+            doubleclick_event(event);
+        } else {
+            m_click_clock.start();
+        }
     }
 }
 
@@ -174,6 +176,13 @@ void GWidget::handle_mousedown_event(GMouseEvent& event)
 {
     if (accepts_focus())
         set_focus(true);
+    if (event.button() == GMouseButton::Right) {
+        if (m_context_menu) {
+            m_context_menu->popup(screen_relative_rect().location().translated(event.position()));
+            return;
+        }
+    }
+    // FIXME: Maybe the click clock should be per-button.
     if (!m_click_clock.is_valid())
         m_click_clock.start();
     mousedown_event(event);
@@ -416,3 +425,10 @@ void GWidget::set_enabled(bool enabled)
     m_enabled = enabled;
     update();
 }
+
+void GWidget::set_context_menu(OwnPtr<GMenu>&& context_menu)
+{
+    // FIXME: Support switching context menus.
+    ASSERT(!m_context_menu);
+    m_context_menu = move(context_menu);
+}

LibGUI/GWidget.h

@@ -11,6 +11,7 @@
 
 class GraphicsBitmap;
 class GLayout;
+class GMenu;
 class GWindow;
 
 enum class SizePolicy { Fixed, Fill };
@@ -41,6 +42,9 @@ public:
     bool is_enabled() const { return m_enabled; }
     void set_enabled(bool);
 
+    const GMenu* context_menu() const { return m_context_menu.ptr(); }
+    void set_context_menu(OwnPtr<GMenu>&&);
+
     virtual void event(CEvent&) override;
     virtual void paint_event(GPaintEvent&);
     virtual void resize_event(GResizeEvent&);
@@ -186,4 +190,5 @@ private:
     bool m_enabled { true };
 
     CElapsedTimer m_click_clock;
+    OwnPtr<GMenu> m_context_menu;
 };