Enabled listbox scrolling with a mouse wheel.

Now it's possible to scroll in a listbox with the scrollwheel of a
mouse. Thanks to boucman for testing.

changelog

@@ -23,6 +23,7 @@ Version 1.5.7+svn:
    * Fix the calculate feature in the test scenario.
    * Fix an endian issue which rendered text wrong on big endian machines.
    * A backspace in a textbox with selection, now clears the selection.
+   * Scrollwheel mouses can scroll the new listboxes.
 
 Version 1.5.7:
  * Campaigns:

src/gui/widgets/event_executor.hpp

@@ -160,6 +160,28 @@ public:
 	/** See mouse_left_button_double_click. */
 	virtual void mouse_right_button_double_click(tevent_handler&) {}
 
+	/***** ***** ***** ***** mouse wheel ***** ***** ***** *****/
+
+	/**
+	 * Scrollwheel up.
+	 *
+	 * The scrollwheel events are trigger by the scrollwheel.
+	 *
+	 * @param event_handler       The event handler that send the event.
+	 * @param handled             Do we handle the event.
+	 */
+	virtual void mouse_wheel_up(
+			tevent_handler& /*event_handler*/, bool& /*handled*/) {}
+
+	/** Scrollwheel down see mouse_wheel_up.*/
+	virtual void mouse_wheel_down(tevent_handler&, bool&) {}
+
+	/** Scrollwheel to the left see mouse_wheel_up.*/
+	virtual void mouse_wheel_left(tevent_handler&, bool&) {}
+
+	/** Scrollwheel to the right see mouse_wheel_up.*/
+	virtual void mouse_wheel_right(tevent_handler&, bool&) {}
+
 	/***** ***** ***** ***** focus ***** ***** ***** *****/
 
 	/**

src/gui/widgets/event_handler.cpp

@@ -150,6 +150,16 @@ void tevent_handler::handle_event(const SDL_Event& event)
 
 		case SDL_MOUSEBUTTONDOWN:
 
+			// The wheel buttons generate and up and down event we handle the
+			// up event so ignore the mouse if it's a down event
+			if(event.button.button == SDL_BUTTON_WHEELUP
+					|| event.button.button == SDL_BUTTON_WHEELDOWN
+					|| event.button.button == SDL_BUTTON_WHEELLEFT
+					|| event.button.button == SDL_BUTTON_WHEELRIGHT) {
+
+				break;
+			}
+
 			mouse_x_ = event.button.x;
 			mouse_y_ = event.button.y;
 			mouse_over = find_widget(tpoint(mouse_x_, mouse_y_), true);
@@ -184,8 +194,7 @@ void tevent_handler::handle_event(const SDL_Event& event)
 					// cast to avoid being printed as char.
 					WRN_G_E << "Unhandled 'mouse button down' event for button "
 						<< static_cast<Uint32>(event.button.button) << ".\n";
-					// The scrollwheel also behaves like a button, so ignore it.
-//					assert(false);
+					assert(false);
 					break;
 			}
 			break;
@@ -219,12 +228,19 @@ void tevent_handler::handle_event(const SDL_Event& event)
 					DBG_G_E << "Event: Right button up.\n";
 					mouse_button_up(event, mouse_over, right_);
 					break;
+				case SDL_BUTTON_WHEELUP :
+				case SDL_BUTTON_WHEELDOWN :
+				case SDL_BUTTON_WHEELLEFT :
+				case SDL_BUTTON_WHEELRIGHT :
+					DBG_G_E << "Event: Wheel\n";
+					mouse_wheel(event,
+							find_widget(tpoint(mouse_x_, mouse_y_), false));
+					break;
 				default:
 					// cast to avoid being printed as char.
 					WRN_G_E << "Unhandled 'mouse button up' event for button "
 						<< static_cast<Uint32>(event.button.button) << ".\n";
-					// The scrollwheel also behaves like a button, so ignore it.
-//					assert(false);
+					assert(false);
 					break;
 			}
 			break;
@@ -533,6 +549,49 @@ void tevent_handler::mouse_click(twidget* widget, tmouse_button& button)
 	}
 }
 
+void tevent_handler::mouse_wheel(const SDL_Event& event, twidget* widget)
+{
+	// If widget == NULL the loop won't run so no need for an explicit test.
+	bool handled = false;
+	while(widget != NULL && !handled) {
+
+		tcontrol* control = dynamic_cast<tcontrol*>(widget);
+		if(!control || control->get_active()) {
+
+			switch(event.button.button) {
+				case SDL_BUTTON_WHEELUP :
+					DBG_G_E << "Event: Wheel up.\n";
+					widget->mouse_wheel_up(*this, handled);
+					break;
+				case SDL_BUTTON_WHEELDOWN :
+					DBG_G_E << "Event: Wheel down.\n";
+					widget->mouse_wheel_down(*this, handled);
+					break;
+				case SDL_BUTTON_WHEELLEFT :
+					DBG_G_E << "Event: Wheel left.\n";
+					widget->mouse_wheel_left(*this, handled);
+					break;
+				case SDL_BUTTON_WHEELRIGHT :
+					DBG_G_E << "Event: Wheel right.\n";
+					widget->mouse_wheel_right(*this, handled);
+					break;
+				default:
+					// cast to avoid being printed as char.
+					WRN_G_E << "Unhandled wheel event for button "
+						<< static_cast<Uint32>(event.button.button) << ".\n";
+					assert(false);
+					break;
+			}
+		}
+
+		// If we handled the window abort.
+		if(dynamic_cast<twindow*>(widget)) {
+			return;
+		}
+		widget = widget->parent();
+	}
+}
+
 void tevent_handler::focus_parent_container(twidget* widget)
 {
 	assert(widget);

src/gui/widgets/event_handler.hpp

@@ -310,6 +310,22 @@ private:
 	 */
 	void mouse_click(twidget* widget, tmouse_button& button);
 
+	/**
+	 * Called when a scroll wheel is scrolled.
+	 *
+	 * The wheel event is always send to the widget underneath the mouse and
+	 * ignores the focus. If a widget doesn't handle the event it's send to
+	 * its parent. The event won't escape the current window. The event moves
+	 * up through inactive widgets.
+	 *
+	 * @todo document this event in the event handling document.
+	 *
+	 * @param event               The SDL_Event which was triggered.
+	 * @param widget              The widget the mouse is over, this widget
+	 *                            might not be active and be NULL so the code
+	 *                            needs to test for it.
+	 */
+	void mouse_wheel(const SDL_Event& event, twidget* widget);
 
 	/**
 	 * Called when a mouse button is pressed.

src/gui/widgets/scrollbar_container.cpp

@@ -639,6 +639,54 @@ void tscrollbar_container::set_scrollbar_button_status()
 	}
 }
 
+void tscrollbar_container::
+		mouse_wheel_up(tevent_handler& /*event_handler*/, bool& handled)
+{
+	assert(vertical_scrollbar_grid_ && vertical_scrollbar_);
+
+	if(vertical_scrollbar_grid_->is_visible()) {
+		vertical_scrollbar_->scroll(tscrollbar_::HALF_JUMP_BACKWARDS);
+		scrollbar_moved();
+		handled = true;
+	}
+}
+
+void tscrollbar_container::
+		mouse_wheel_down(tevent_handler& /*event_handler*/, bool& handled)
+{
+	assert(vertical_scrollbar_grid_ && vertical_scrollbar_);
+
+	if(vertical_scrollbar_grid_->is_visible()) {
+		vertical_scrollbar_->scroll(tscrollbar_::HALF_JUMP_FORWARD);
+		scrollbar_moved();
+		handled = true;
+	}
+}
+
+void tscrollbar_container::
+		mouse_wheel_left(tevent_handler& /*event_handler*/, bool& handled)
+{
+	assert(horizontal_scrollbar_grid_ && horizontal_scrollbar_);
+
+	if(horizontal_scrollbar_grid_->is_visible()) {
+		horizontal_scrollbar_->scroll(tscrollbar_::HALF_JUMP_BACKWARDS);
+		scrollbar_moved();
+		handled = true;
+	}
+}
+
+void tscrollbar_container::
+		mouse_wheel_right(tevent_handler& /*event_handler*/, bool& handled)
+{
+	assert(horizontal_scrollbar_grid_ && horizontal_scrollbar_);
+
+	if(horizontal_scrollbar_grid_->is_visible()) {
+		horizontal_scrollbar_->scroll(tscrollbar_::HALF_JUMP_FORWARD);
+		scrollbar_moved();
+		handled = true;
+	}
+}
+
 void tscrollbar_container::handle_key_home(SDLMod /*modifier*/, bool& handled)
 {
 	assert(vertical_scrollbar_ && horizontal_scrollbar_);

src/gui/widgets/scrollbar_container.hpp

@@ -198,6 +198,20 @@ protected:
 	 */
 	void set_scrollbar_button_status();
 
+	/***** ***** ***** ***** mouse wheel functions ***** ***** ***** *****/
+
+	/** Inherited from tevent_executor. */
+	void mouse_wheel_up(tevent_handler& event_handler, bool& handled);
+
+	/** Inherited from tevent_executor. */
+	void mouse_wheel_down(tevent_handler& event_handler, bool& handled);
+
+	/** Inherited from tevent_executor. */
+	void mouse_wheel_left(tevent_handler& event_handler, bool& handled);
+
+	/** Inherited from tevent_executor. */
+	void mouse_wheel_right(tevent_handler& event_handler, bool& handled);
+
 	/***** ***** ***** ***** keyboard functions ***** ***** ***** *****/
 
 	/**