Class Rubygame::Screen
In: lib/rubygame/screen.rb
Parent: Rubygame::Surface

Screen represents the display window for the game. The Screen is a special Surface that is displayed to the user. By changing and then updating the Screen many times per second, you can create the illusion of continous motion.

Screen inherits most of the Surface methods, and can be passed to methods which expect a Surface, including Surface#blit. However, the Screen cannot have an alpha channel or a colorkey, so Surface#alpha=, Surface#set_alpha, Surface#colorkey=, and Surface#set_colorkey are not inherited.

Please note that only one Screen can exist at a time, per application; this is a limitation of SDL. Use (or its alias, to create or modify the Screen.

Also note that no changes to the Screen will be seen until it is refreshed. See update, update_rects, and flip for ways to refresh all or part of the Screen.


External Aliases

new -> open

Public Class methods

Close the Screen, making the Rubygame window disappear. This method also exits from fullscreen mode, if needed.

After calling this method, you should discard any references to the old Screen surface, as it is no longer valid, even if you call again.

(Note: You do not need to close the Screen to change its size or flags, you can simply call while already open.)


# File lib/rubygame/screen.rb, line 91
    def close
      SDL.QuitSubSystem( SDL::INIT_VIDEO )

Returns the pixel dimensions of the user’s display (i.e. monitor). (That is not the same as Screen#size, which only measures the Rubygame window.) You can use this information to detect how large of a Screen can fit on the user’s display.

This method can only be used when there is no open Screen instance. This method raises SDLError if there is a Screen instance (i.e. you have done before). This is a limitation of the SDL function SDL_GetVideoInfo, which behaves differently when a Screen is open than when it is closed.

This method will also raise SDLError if it cannot get the display size for some other reason.


# File lib/rubygame/screen.rb, line 134
    def get_resolution
      if( Rubygame.init_video_system() != 0 )
        raise(Rubygame::SDLError, "Could not initialize SDL video subsystem.")

      unless SDL.GetVideoSurface().pointer.null?
        raise( Rubygame::SDLError, "You cannot get resolution when there " +
               "is an open Screen. See the docs for the reason." )

      info = SDL::GetVideoInfo()
      if( info.pointer.null? )
        raise Rubygame::SDLError, "Couldn't get video info: #{SDL.GetError()}"

      return [info.current_w, info.current_h]

Returns the currently open Screen, or raises SDLError if it fails to get it (for example, if it doesn’t exist yet).


# File lib/rubygame/screen.rb, line 108
    def get_surface
      s = SDL.GetVideoSurface()

      if s.pointer.null?
        raise( Rubygame::SDLError,
               "Couldn't get video surface: #{SDL.GetError()}" )

      return s )

Deprecated alias for This method will be REMOVED in Rubygame 3.0. You should use (or its alias, instead.


# File lib/rubygame/screen.rb, line 76
    def instance( size, depth=0, flags=[Rubygame::SWSURFACE] )
      Rubygame.deprecated("Rubygame::Screen.instance", "3.0")
      new( size, depth, flags )

Create a new Rubygame window if there is none, or modify the existing one. You cannot create more than one Screen; the existing one will be replaced. (This is a limitation of SDL.)

Returns the resulting Screen.

size:requested window size (in pixels), in the form [width,height]
depth:requested color depth (in bits per pixel). If 0 (default), the current system color depth.
flags:an Array of zero or more of the following flags (located under the Rubygame module).
SWSURFACE:Create the video surface in system memory.
HWSURFACE:Create the video surface in video memory.
ASYNCBLIT:Enables the use of asynchronous updates of the display surface. This will usually slow down blitting on single CPU machines, but may provide a speed increase on SMP systems.
ANYFORMAT:Normally, if a video surface of the requested bits-per-pixel (bpp) is not available, Rubygame will emulate one with a shadow surface. Passing ANYFORMAT prevents this and causes Rubygame to use the video surface regardless of its depth.
DOUBLEBUF:Enable hardware double buffering; only valid with HWSURFACE. Calling flip will flip the buffers and update the screen. All drawing will take place on the surface that is not displayed at the moment. If double buffering could not be enabled then flip will just update the entire screen.
FULLSCREEN:Rubygame will attempt to use a fullscreen mode. If a hardware resolution change is not possible (for whatever reason), the next higher resolution will be used and the display window centered on a black background.
OPENGL:Create an OpenGL rendering context. You must set proper OpenGL video attributes with GL#set_attrib before calling this method with this flag. You can then use separate opengl libraries (for example rbogl) to do all OpenGL-related functions. Please note that you can’t blit or draw regular SDL Surfaces onto an OpenGL-mode screen; you must use OpenGL functions.
RESIZABLE:Create a resizable window. When the window is resized by the user, a ResizeEvent is generated and this method can be called again with the new size.
NOFRAME:If possible, create a window with no title bar or frame decoration. Fullscreen modes automatically have this flag set.


# File lib/rubygame/screen.rb, line 207
  def initialize(  size, depth=0, flags=[Rubygame::SWSURFACE] )

    # Cheating a bit. First arg can be a SDL::Surface to wrap it.
    if( size.kind_of? SDL::Surface )
      surf = size
      if( surf.pointer.null? )
        raise Rubygame::SDLError, "Screen cannot wrap NULL Surface!"
      elsif( surf.pointer != SDL.GetVideoSurface().pointer )
        raise Rubygame::SDLError, "Screen can only wrap the video Surface!"
        @struct = surf

    w,h = size
    flags = Rubygame.collapse_flags(flags)

    @struct = SDL.SetVideoMode( w, h, depth, flags )

    if( @struct.pointer.null? )
      @struct = nil
      raise( Rubygame::SDLError,
             "Couldn't set [%d x %d] %d bpp video mode: %s"%\
             [w, h, depth, SDL.GetError()] )


True if there is an open Rubygame window. See and Screen.close.


# File lib/rubygame/screen.rb, line 100
    def open?
      (not SDL.GetVideoSurface().pointer.null?)

Deprecated alias for This method will be REMOVED in Rubygame 3.0. You should use (or its alias, instead.


# File lib/rubygame/screen.rb, line 67
    def set_mode( size, depth=0, flags=[Rubygame::SWSURFACE] )
      Rubygame.deprecated("Rubygame::Screen.set_mode", "3.0")
      new( size, depth, flags )

Public Instance methods

If the Rubygame display is double-buffered (see, flips the buffers and updates the whole screen. Otherwise, just updates the whole screen.


# File lib/rubygame/screen.rb, line 244
  def flip
    SDL.Flip( @struct )

Sets the window icon for the Screen.

icon:a Rubygame::Surface to be displayed at the top of the Rubygame window (when not in fullscreen mode), and in other OS-specific areas (like the taskbar entry). If omitted or nil, no icon will be shown at all.

NOTE: The SDL docs state that icons on Win32 systems must be 32x32 pixels. That may or may not be true anymore, but you might want to consider it when creating games to run on Windows.


# File lib/rubygame/screen.rb, line 328
  def icon=( surface )
    SDL.WM_SetIcon( surface.struct, nil )
    return self

Set whether the mouse cursor is displayed or not. If value is true, the cursor will be shown; if false, it will be hidden. See also show_cursor?


# File lib/rubygame/screen.rb, line 347
  def show_cursor=( value )
    value = value ? SDL::ENABLE : SDL::DISABLE
    return ( SDL.ShowCursor(value) == SDL::ENABLE )

Returns true if the mouse cursor is shown, or false if hidden. See also show_cursor=


# File lib/rubygame/screen.rb, line 338
  def show_cursor?
    return ( SDL.ShowCursor(SDL::QUERY) == 1 )

Returns the current window title for the Screen. The default is an empty string.


# File lib/rubygame/screen.rb, line 357
  def title
    return SDL.WM_GetCaption()[0]

Sets the window title for the Screen.

newtitle:a string, (usually) displayed at the top of the Rubygame window (when not in fullscreen mode). If omitted or nil, title will be an empty string. How this string is displayed (if at all) is system-dependent.


# File lib/rubygame/screen.rb, line 369
  def title=( newtitle )
    SDL.WM_SetCaption( newtitle, newtitle )

Updates (refreshes) all or part of the Rubygame window, revealing to the user any changes that have been made since the last update. If you’re using a double-buffered display (see, you should use Screen#flip instead.

rect:a Rubygame::Rect representing the area of the screen to update. Can also be an length-4 Array, or given as 4 separate arguments. If omitted or nil, the entire screen is updated.


# File lib/rubygame/screen.rb, line 264
  def update( *args )
    r = case args[0]
        when nil
          # Update the whole screen. Skip the stuff below.
          SDL.UpdateRect( @struct, 0, 0, 0, 0 );
          return self
        when SDL::Rect
 args[0].to_ary )
        when Array
 args[0] )
        when Numeric
 args[0,4] )
          raise( ArgumentError,
                 "Invalid args for #{self.class}#update: #{args.inspect}" )

    SDL.UpdateRect( @struct, *(r.clip!( self.make_rect ).to_sdl) );

    return self

Updates (as Screen#update does) several areas of the screen.

rects:an Array containing any number of Rect objects, each rect representing a portion of the screen to update.


# File lib/rubygame/screen.rb, line 293
  def update_rects( rects )
    my_rect = self.make_rect

    rects.collect! do |r|
      r = case r
          when SDL::Rect
   r.to_ary )
          when Array
   r )
            raise( ArgumentError,
                   "Invalid rect for #{self.class}#update_rects: #{r.inspect}" )


    SDL.UpdateRects( @struct, rects )

    return self