A workaround to allow users not using 16BPP to change video mode

src/game.cpp

@@ -315,6 +315,7 @@ int play_game(int argc, char** argv)
 
 	std::cerr << "setting mode to " << resolution.first << "x" << resolution.second << "\n";
 	const int res = video.setMode(resolution.first,resolution.second,16,video_flags);
+	video.setBpp(bpp);
 	if(res != 16) {
 		std::cerr << "required video mode, " << resolution.first << "x"
 		          << resolution.second << "x16 is not supported\n";

src/preferences.cpp

@@ -595,6 +595,7 @@ bool show_video_mode_dialog(display& disp)
 	std::vector<std::string> options;
 
 	CVideo& video = disp.video();
+	video.setBitsPerPixel(video.getBpp());
 	SDL_Rect** modes = SDL_ListModes(video.getSurface()->format,FULL_SCREEN);
 
 	//the SDL documentation says that a return value of -1 if no dimension

src/video.cpp

@@ -128,7 +128,7 @@ void update_whole_screen()
 {
 	update_all = true;
 }
-CVideo::CVideo() : frameBuffer(NULL)
+CVideo::CVideo() : frameBuffer(NULL), bpp(0)
 {
 	const int res = SDL_Init(SDL_INIT_VIDEO | SDL_INIT_AUDIO | SDL_INIT_NOPARACHUTE);
 
@@ -139,7 +139,7 @@ CVideo::CVideo() : frameBuffer(NULL)
 }
 
 CVideo::CVideo( int x, int y, int bits_per_pixel, int flags)
-		 : frameBuffer(NULL)
+		 : frameBuffer(NULL), bpp(0)
 {
 	const int res = SDL_Init( SDL_INIT_VIDEO | SDL_INIT_AUDIO | SDL_INIT_NOPARACHUTE);
 	if(res < 0) {
@@ -245,3 +245,18 @@ SDL_Surface* CVideo::getSurface( void )
 }
 
 bool CVideo::isFullScreen() const { return fullScreen; }
+
+void CVideo::setBitsPerPixel( int bpp )
+{
+	frameBuffer->format->BitsPerPixel = bpp;
+}
+
+void CVideo::setBpp( int bpp )
+{
+	this->bpp = bpp;
+}
+
+int CVideo::getBpp( void )
+{
+	return bpp;
+}

src/video.hpp

@@ -57,9 +57,14 @@ class CVideo {
 
 	struct quit {};
 
+	//functions to allow changing video modes when 16BPP is emulated
+	void setBitsPerPixel( int bpp );
+	void setBpp( int bpp );
+	int getBpp();
      private:
 
 	SDL_Surface* frameBuffer;
+	int bpp;	// Store real bits per pixel
 };
 
 #endif