Index: dataobj/environment.cc
===================================================================
--- dataobj/environment.cc	(revisión: 10142)
+++ dataobj/environment.cc	(copia de trabajo)
@@ -17,6 +17,7 @@
 void rdwr_win_settings(loadsave_t *file); // simwin
 
 sint16 env_t::menupos = MENU_TOP;
+bool env_t::fullscreen = false;
 bool env_t::reselect_closes_tool = true;
 
 sint8 env_t::pak_tile_height_step = 16;
@@ -559,6 +560,8 @@
 		file->rdwr_bool( single_line_gui );
 
 		file->rdwr_byte( show_factory_storage_bar );
+ 
+		file->rdwr_bool( fullscreen );
 	}
 
 	// server settings are not saved, since they are server specific
Index: dataobj/environment.h
===================================================================
--- dataobj/environment.h	(revisión: 10142)
+++ dataobj/environment.h	(copia de trabajo)
@@ -37,6 +37,8 @@
 
 	static sint16 menupos;
 
+	static bool fullscreen;
+
 	static bool reselect_closes_tool;
 
 	/// points to the current user directory for loading and saving
Index: gui/display_settings.cc
===================================================================
--- gui/display_settings.cc	(revisión: 10142)
+++ gui/display_settings.cc	(copia de trabajo)
@@ -18,6 +18,7 @@
 #include "../simmenu.h"
 #include "../player/simplay.h"
 #include "../utils/simstring.h"
+#include "../sys/simsys.h"
 
 #include "gui_theme.h"
 #include "themeselector.h"
@@ -104,6 +105,10 @@
 	}
 	add_component(&toolbar_pos);
 
+	fullscreen.init( button_t::square_state, "Fullscreen" );
+	fullscreen.pressed = is_fullscreen();
+	add_component( &fullscreen, 2 );
+
 	reselect_closes_tool.init( button_t::square_state, "Reselect closes tools" );
 	reselect_closes_tool.pressed = env_t::reselect_closes_tool;
 	add_component( &reselect_closes_tool, 2 );
@@ -498,6 +503,7 @@
 		buttons[ i ].add_listener( this );
 	}
 	gui_settings.toolbar_pos.add_listener( this );
+	gui_settings.fullscreen.add_listener( this );
 	gui_settings.reselect_closes_tool.add_listener(this);
 
 	set_resizemode(diagonal_resize);
@@ -528,6 +534,12 @@
 		return true;
 	}
 
+	if(  comp == &gui_settings.fullscreen  ) {
+		env_t::fullscreen = toggle_fullscreen();
+		gui_settings.fullscreen.pressed = is_fullscreen();
+		return true;
+	}
+
 	if(  comp == &gui_settings.reselect_closes_tool  ) {
 		env_t::reselect_closes_tool = !env_t::reselect_closes_tool;
 		gui_settings.reselect_closes_tool.pressed = env_t::reselect_closes_tool;
Index: gui/display_settings.h
===================================================================
--- gui/display_settings.h	(revisión: 10142)
+++ gui/display_settings.h	(copia de trabajo)
@@ -29,7 +29,7 @@
 		simloops_value_label;
 
 public:
-	button_t toolbar_pos, reselect_closes_tool;
+	button_t toolbar_pos, reselect_closes_tool, fullscreen;
 
 	gui_settings_t();
 	void draw( scr_coord offset ) OVERRIDE;
Index: simmain.cc
===================================================================
--- simmain.cc	(revisión: 10142)
+++ simmain.cc	(copia de trabajo)
@@ -889,6 +889,8 @@
 	}
 
 	fullscreen |= args.has_arg("-fullscreen");
+	// Only will be true if it has been set previously via GUI
+	fullscreen |= env_t::fullscreen;
 
 	if(args.has_arg("-screensize")) {
 		const char* res_str = args.gimme_arg("-screensize", 1);
Index: sys/simsys.h
===================================================================
--- sys/simsys.h	(revisión: 10142)
+++ sys/simsys.h	(copia de trabajo)
@@ -216,6 +216,17 @@
 ///  returns current two byte languange ID
 const char* dr_get_locale();
 
+/** 
+ * Returns fullscreen state
+ */
+bool is_fullscreen();
+
+/** 
+ * Toggle fullscreen mode
+ * Returns the fullscreen state after the toggle
+ */
+bool toggle_fullscreen();
+
 int sysmain(int argc, char** argv);
 
 #endif
Index: sys/simsys_d.cc
===================================================================
--- sys/simsys_d.cc	(revisión: 10142)
+++ sys/simsys_d.cc	(copia de trabajo)
@@ -23,6 +23,7 @@
 
 static int width  = 800;
 static int height = 600;
+static int fullscreen = false;
 
 
 /* event-handling */
@@ -223,10 +224,11 @@
 }
 
 
-int dr_os_open(int const w, int const h, bool fullscreen)
+int dr_os_open(int const w, int const h, bool fs)
 {
 	width = w;
 	height = h;
+	fullscreen = fs;
 
 	install_keyboard();
 
@@ -470,7 +472,16 @@
 	return "";
 }
 
+bool is_fullscreen()
+{
+	return fullscreen;
+}
 
+bool toggle_fullscreen()
+{
+	return fullscreen;
+}
+
 int main(int argc, char **argv)
 {
 	return sysmain(argc, argv);
Index: sys/simsys_posix.cc
===================================================================
--- sys/simsys_posix.cc	(revisión: 10142)
+++ sys/simsys_posix.cc	(copia de trabajo)
@@ -186,7 +186,16 @@
 	return "";
 }
 
+bool is_fullscreen()
+{
+	return false;
+}
 
+bool toggle_fullscreen()
+{
+	return false;
+}
+
 int main(int argc, char **argv)
 {
 	signal( SIGTERM, posix_sigterm );
Index: sys/simsys_s.cc
===================================================================
--- sys/simsys_s.cc	(revisión: 10142)
+++ sys/simsys_s.cc	(copia de trabajo)
@@ -78,6 +78,7 @@
 static SDL_Surface *screen;
 static int width = 16;
 static int height = 16;
+static bool fullscreen = false;
 
 // switch on is a little faster (<3%)
 static int async_blit = 0;
@@ -236,7 +237,7 @@
 
 
 // open the window
-int dr_os_open(int w, int const h, bool fullscreen)
+int dr_os_open(int w, int const h, bool fs)
 {
 #ifdef MULTI_THREAD
 	// init barrier
@@ -269,6 +270,7 @@
 
 	width = w;
 	height = h;
+	fullscreen = fs;
 
 	flags |= (fullscreen ? SDL_FULLSCREEN : SDL_RESIZABLE);
 	if(  use_hw  ) {
@@ -739,6 +741,16 @@
 	return NULL;
 }
 
+bool is_fullscreen()
+{
+	return fullscreen;
+}
+
+bool toggle_fullscreen()
+{
+	return fullscreen;
+}
+
 #ifdef _MSC_VER
 // Needed for MS Visual C++ with /SUBSYSTEM:CONSOLE to work , if /SUBSYSTEM:WINDOWS this function is compiled but unreachable
 #undef main
Index: sys/simsys_s2.cc
===================================================================
--- sys/simsys_s2.cc	(revisión: 10142)
+++ sys/simsys_s2.cc	(copia de trabajo)
@@ -105,6 +105,7 @@
 
 static int sync_blit = 0;
 static int use_dirty_tiles = 1;
+static bool fullscreen = false;
 
 static SDL_Cursor *arrow;
 static SDL_Cursor *hourglass;
@@ -296,12 +297,14 @@
 
 
 // open the window
-int dr_os_open(int screen_width, int screen_height, bool fullscreen)
+int dr_os_open(int screen_width, int screen_height, bool fs)
 {
 	// scale up
 	const int tex_w = SCREEN_TO_TEX_X(screen_width);
 	const int tex_h = SCREEN_TO_TEX_Y(screen_height);
 
+	fullscreen = fs;
+
 	// some cards need those alignments
 	// especially 64bit want a border of 8bytes
 	const int tex_pitch = max((tex_w + 15) & 0x7FF0, 16);
@@ -938,7 +941,18 @@
 	return NULL;
 }
 
+bool is_fullscreen()
+{
+	return fullscreen;
+}
 
+bool toggle_fullscreen()
+{
+	SDL_SetWindowFullscreen(window, fullscreen ? 0 : SDL_WINDOW_FULLSCREEN_DESKTOP);
+	fullscreen = !fullscreen;
+	return fullscreen;
+}
+
 #ifdef _MSC_VER
 // Needed for MS Visual C++ with /SUBSYSTEM:CONSOLE to work , if /SUBSYSTEM:WINDOWS this function is compiled but unreachable
 #undef main
Index: sys/simsys_w.cc
===================================================================
--- sys/simsys_w.cc	(revisión: 10142)
+++ sys/simsys_w.cc	(copia de trabajo)
@@ -53,7 +53,7 @@
 static const LPCWSTR WINDOW_CLASS_NAME = L"Simu";
 
 static volatile HWND hwnd;
-static bool is_fullscreen = false;
+static bool fullscreen = false;
 static bool is_not_top = false;
 static MSG msg;
 static RECT WindowSize = { 0, 0, 0, 0 };
@@ -145,10 +145,11 @@
 
 
 // open the window
-int dr_os_open(int const w, int const h, bool fullscreen)
+int dr_os_open(int const w, int const h, bool fs)
 {
 	MaxSize.right = ((w*x_scale)/32+15) & 0x7FF0;
 	MaxSize.bottom = (h*y_scale)/32;
+	fullscreen = fs;
 
 #ifdef MULTI_THREAD
 	InitializeCriticalSection( &redraw_underway );
@@ -182,7 +183,6 @@
 		else {
 			ChangeDisplaySettings(&settings, CDS_FULLSCREEN);
 		}
-		is_fullscreen = fullscreen;
 	}
 	if(  fullscreen  ) {
 		create_window(WS_EX_TOPMOST, WS_POPUP, 0, 0, MaxSize.right, MaxSize.bottom);
@@ -239,7 +239,7 @@
 	AllDibData = NULL;
 	free(AllDib);
 	AllDib = NULL;
-	if(  is_fullscreen  ) {
+	if(  fullscreen  ) {
 		ChangeDisplaySettings(NULL, 0);
 	}
 }
@@ -426,7 +426,7 @@
 			return 0;
 
 		case WM_ACTIVATE: // may check, if we have to restore color depth
-			if(is_fullscreen) {
+			if(fullscreen) {
 				// avoid double calls
 				static bool while_handling = false;
 				if(while_handling) {
@@ -479,7 +479,7 @@
 			break;
 
 		case WM_GETMINMAXINFO:
-			if(is_fullscreen) {
+			if(fullscreen) {
 				LPMINMAXINFO lpmmi = (LPMINMAXINFO) lParam;
 				lpmmi->ptMaxPosition.x = 0;
 				lpmmi->ptMaxPosition.y = 0;
@@ -974,7 +974,16 @@
 	return LanguageCode;
 }
 
+bool is_fullscreen()
+{
+	return fullscreen;
+}
 
+bool toggle_fullscreen()
+{
+	return fullscreen;
+}
+
 int CALLBACK WinMain(HINSTANCE const hInstance, HINSTANCE, LPSTR, int)
 {
 	WNDCLASSW wc;