GUI2/Listbox: added select_row_at function

See header docs for explanation.

src/gui/widgets/listbox.cpp

@@ -261,6 +261,13 @@ bool listbox::select_row(const unsigned row, const bool select)
 	return before != generator_->get_selected_item_count();
 }
 
+bool listbox::select_row_at(const unsigned row, const bool select)
+{
+	assert(generator_);
+
+	return select_row(generator_->get_item_at_ordered(row), select);
+}
+
 bool listbox::row_selected(const unsigned row)
 {
 	assert(generator_);
@@ -636,7 +643,7 @@ void listbox::set_active_sorting_option(const order_pair& sort_by, const bool se
 	order_by_column(sort_by.first, dynamic_cast<widget&>(wgt));
 
 	if(select_first && generator_->get_item_count() > 0) {
-		select_row(generator_->get_item_at_ordered(0));
+		select_row_at(0);
 	}
 }
 

src/gui/widgets/listbox.hpp

@@ -184,6 +184,24 @@ class listbox : public scrollbar_container
 	 */
 	bool select_row(const unsigned row, const bool select = true);
 
+	/**
+	 * Selects a row at the given position, regardless of sorting order.
+	 *
+	 * When using @ref select_row the relevant row is located by index regardless
+	 * of its actual position in the list, which could differ if the list had been
+	 * sorted. In that case, `select_row(0)` would not select the list's first row
+	 * as displayed.
+	 *
+	 * This function allows row selection based on position. `select_row_at(0)` will
+	 * always select the list's first row, regardless of sorting order.
+	 *
+	 * @param row                 The row to select.
+	 * @param select              Select or deselect the row.
+	 *
+	 * @returns                   True if the operation succeeded.
+	 */
+	bool select_row_at(const unsigned row, const bool select = true);
+
 	/**
 	 * Check if a row is selected
 	 * @param row                 The row to test