Client|MenuWidget: Added an optional sort order for menu items

Any object that implements ISortOrder can be used as the sort order
for menu items.

doomsday/client/include/ui/widgets/menuwidget.h

@@ -28,9 +28,30 @@
  * One of the dimensions of the grid can be configured to use ui::Expand
  * policy, but then the child widgets must manage their size on that axis by
  * themselves.
+ *
+ * A sort order for the items can be optionally defined using
+ * MenuWidget::ISortOrder. Sorting affects layout only, not the actual order of
+ * the children.
  */
 class MenuWidget : public ScrollAreaWidget
 {
+public:
+    class ISortOrder
+    {
+    public:
+        virtual ~ISortOrder() {}
+
+        /**
+         * Determines the sort order for a pair of menu items.
+         *
+         * @param a  First menu item.
+         * @param b  Second menu item.
+         *
+         * @return -1 if a < b; +1 if a > b; 0 if equal.
+         */
+        virtual int compareMenuItemsForSorting(Widget const &a, Widget const &b) const = 0;
+    };
+
 public:
     MenuWidget(de::String const &name = "");
 
@@ -57,6 +78,13 @@ class MenuWidget : public ScrollAreaWidget
     void setGridSize(int columns, ui::SizePolicy columnPolicy,
                      int rows, ui::SizePolicy rowPolicy);
 
+    /**
+     * Sets the sort order for item layout.
+     *
+     * @param sorting  Sort order object. MenuWidget takes ownership.
+     */
+    void setLayoutSortOrder(ISortOrder *sorting);
+
     ButtonWidget *addItem(de::String const &styledText, de::Action *action = 0);
 
     ButtonWidget *addItem(de::Image const &image, de::String const &styledText, de::Action *action = 0);

doomsday/client/src/ui/widgets/menuwidget.cpp

@@ -24,6 +24,8 @@ using namespace ui;
 DENG2_PIMPL(MenuWidget)
 {
     bool needLayout;
+    QScopedPointer<ISortOrder> sorting;
+    WidgetList sortedChildren;
 
     SizePolicy colPolicy;
     SizePolicy rowPolicy;
@@ -105,6 +107,8 @@ DENG2_PIMPL(MenuWidget)
         Vector2i size;
         int ord = 0;
 
+        DENG2_ASSERT(sortedChildren.size() == int(self.childCount()));
+
         foreach(Widget *i, self.Widget::children())
         {
             if(isVisibleItem(i))
@@ -116,10 +120,29 @@ DENG2_PIMPL(MenuWidget)
         return size;
     }
 
+    // Functor for quicksort comparisons.
+    struct Sorter {
+        Instance &d;
+        Sorter(Instance *inst) : d(*inst) {}
+        bool operator () (Widget const *a, Widget const *b) const {
+            DENG2_ASSERT(!d.sorting.isNull());
+            return d.sorting->compareMenuItemsForSorting(*a, *b) < 0;
+        }
+    };
+
+    void prepareSortedChildren()
+    {
+        sortedChildren = self.Widget::children();
+        if(!sorting.isNull())
+        {
+            qSort(sortedChildren.begin(), sortedChildren.end(), Sorter(this));
+        }
+    }
+
     GuiWidget *findItem(int col, int row) const
     {
         int ord = 0;
-        foreach(Widget *i, self.Widget::children())
+        foreach(Widget *i, sortedChildren)
         {
             if(isVisibleItem(i))
             {
@@ -234,6 +257,12 @@ void MenuWidget::setGridSize(int columns, ui::SizePolicy columnPolicy,
     d->needLayout = true;
 }
 
+void MenuWidget::setLayoutSortOrder(ISortOrder *sorting)
+{
+    d->sorting.reset(sorting);
+    d->needLayout = true;
+}
+
 ButtonWidget *MenuWidget::addItem(String const &styledText, Action *action)
 {
     return addItem(Image(), styledText, action);
@@ -278,7 +307,8 @@ int MenuWidget::count() const
 
 void MenuWidget::updateLayout()
 {
-    //qDebug() << path().toString() << "Menu has" << d->countVisible() << "visible items";
+    // Sort children again.
+    d->prepareSortedChildren();
 
     Rule const *baseVert = holdRef(&contentRule().top());
 

doomsday/client/src/ui/widgets/popupmenuwidget.cpp

@@ -150,9 +150,9 @@ void PopupMenuWidget::preparePopupForOpening()
     PopupWidget::preparePopupForOpening();
 
     // Redo the layout.
+    menu().updateLayout();
     menu().rule().setInput(Rule::Width,
                            *refless(menu().newColumnWidthRule(0)) + 2 * margin());
-    menu().updateLayout();
 }
 
 void PopupMenuWidget::popupClosing()