ScreenManager class

The ScreenManager class defines the interface required for managing the UI system in Robot Devastation. Other classes can then define the implementation of the ScreenManager according to, for instance, the library selected for displaying graphics on the screen.

The main methods of a ScreenManager are:

• start(), stop() and isStopped(): control the manager startup and halting.

• configure(): configure some UI parameters (e.g. to enable fullscreen mode).

• setCurrentScreen(): sets a Screen to be displayed.

• show(): display the currently selected Screen.

• update(): updates some UI aspect. Currently, several signatures are used as they are required by the corresponding Screen. An alternative implementation could use void * or templates to simplify the API, leaving a single update() method.

SDLScreenManager class

SDLScreenManager is an implementation of the ScreenManager interface using SDL to display graphics.

About the SDL graphics loop

To work properly, SDL requires that all SDL calls (for input, music, graphics, etc) must be performed in the same thread. Otherwise, thread-related exceptions and error start to appear. The typical loop of a SDL program is:

while not exit do
   read inputs
   process inputs, compute actions / consecuences
   process actions
   display / update graphics

Therefore, as SDLScreenManager uses SDL as graphics backend, one must be careful and ensure all the calls to show() occur in the same thread as the input is read.