Add a work-around for SDL_GetAppState in SDL2.

The code only compiles, but never return a sensible value. This should
be done later.

src/sdl/compat.hpp

@@ -37,6 +37,7 @@
 #define KMOD_META KMOD_GUI
 #define SDL_FULLSCREEN SDL_WINDOW_FULLSCREEN_DESKTOP
 #define SDL_EVENTMASK(EVENT) EVENT, EVENT
+#define SDL_GetAppState CVideo::window_state
 
 #endif
 

src/video.cpp

@@ -449,6 +449,33 @@ bool CVideo::update_locked() const
 	return updatesLocked_ > 0;
 }
 
+#if SDL_VERSION_ATLEAST(2, 0, 0)
+static SDL_Window* window = NULL;
+
+Uint8
+CVideo::window_state(void)
+{
+    Uint8 state = 0;
+    Uint32 flags = 0;
+
+	if(!::window) {
+		return state;
+	}
+
+    flags = SDL_GetWindowFlags(::window);
+    if ((flags & SDL_WINDOW_SHOWN) && !(flags & SDL_WINDOW_MINIMIZED)) {
+        state |= SDL_APPACTIVE;
+    }
+    if (flags & SDL_WINDOW_INPUT_FOCUS) {
+        state |= SDL_APPINPUTFOCUS;
+    }
+    if (flags & SDL_WINDOW_MOUSE_FOCUS) {
+        state |= SDL_APPMOUSEFOCUS;
+    }
+    return state;
+}
+#endif
+
 surface& CVideo::getSurface()
 {
 	return frameBuffer;

src/video.hpp

@@ -25,6 +25,12 @@ struct surface;
 //possible flags when setting video modes
 #define FULL_SCREEN SDL_FULLSCREEN
 
+#if SDL_VERSION_ATLEAST(2, 0, 0)
+#define SDL_APPMOUSEFOCUS	0x01		/**< The app has mouse coverage */
+#define SDL_APPINPUTFOCUS	0x02		/**< The app has input focus */
+#define SDL_APPACTIVE		0x04		/**< The application is active */
+#endif
+
 surface display_format_alpha(surface surf);
 surface get_video_surface();
 SDL_Rect screen_area();
@@ -118,6 +124,15 @@ class CVideo : private boost::noncopyable {
 	void lock_updates(bool value);
 	bool update_locked() const;
 
+#if SDL_VERSION_ATLEAST(2, 0, 0)
+	/**
+	 * Wrapper for SDL_GetAppState.
+	 *
+	 * @warning The function always return 0 for now.
+	 */
+	static Uint8 window_state();
+#endif
+
 private:
 
 	void initSDL();