diff --git a/src/posix/sdl/gl_sysfb.h b/src/posix/sdl/gl_sysfb.h
index 6972dd4492..c9c1e81927 100644
--- a/src/posix/sdl/gl_sysfb.h
+++ b/src/posix/sdl/gl_sysfb.h
@@ -26,8 +26,10 @@ public:
 	int GetClientWidth() override;
 	int GetClientHeight() override;
 	void ToggleFullscreen(bool yes) override;
+	void SetWindowSize(int client_w, int client_h);
 
 	SDL_Window *GetSDLWindow() { return Screen; }
+	void GetWindowBordersSize(int &top, int &left);
 
 protected:
 	void SetGammaTable(uint16_t *tbl);
@@ -45,6 +47,14 @@ protected:
 
 	Uint16 m_origGamma[3][256];
 	bool m_supportsGamma;
+
+	static const int MIN_WIDTH = 320;
+	static const int MIN_HEIGHT = 200;
+
+	typedef DECLSPEC int SDLCALL (*SDL_GetWindowBordersSizePtr)(SDL_Window *, int *, int *, int *, int *);
+
+	SDL_GetWindowBordersSizePtr SDL_GetWindowBordersSize_;
+	void *sdl_lib;
 };
 
 #endif // __POSIX_SDL_GL_SYSFB_H__
diff --git a/src/posix/sdl/sdlglvideo.cpp b/src/posix/sdl/sdlglvideo.cpp
index df5e51c611..7eb389ae1c 100644
--- a/src/posix/sdl/sdlglvideo.cpp
+++ b/src/posix/sdl/sdlglvideo.cpp
@@ -88,6 +88,7 @@ CVAR(Int, win_x, -1, CVAR_ARCHIVE | CVAR_GLOBALCONFIG)
 CVAR(Int, win_y, -1, CVAR_ARCHIVE | CVAR_GLOBALCONFIG)
 CVAR(Int, win_w, -1, CVAR_ARCHIVE | CVAR_GLOBALCONFIG)
 CVAR(Int, win_h, -1, CVAR_ARCHIVE | CVAR_GLOBALCONFIG)
+CVAR(Bool, win_maximized, false, CVAR_ARCHIVE | CVAR_GLOBALCONFIG | CVAR_NOINITCALL)
 
 CVAR(Bool, i_soundinbackground, false, CVAR_ARCHIVE | CVAR_GLOBALCONFIG)
 
@@ -181,6 +182,15 @@ IVideo *gl_CreateVideo()
 SystemGLFrameBuffer::SystemGLFrameBuffer (void *, bool fullscreen)
 	: DFrameBuffer (vid_defwidth, vid_defheight)
 {
+	// SDL_GetWindowBorderSize() is only available since 2.0.5, but because
+	// GZDoom supports platforms with older SDL2 versions, this function
+	// has to be dynamically loaded
+	sdl_lib = SDL_LoadObject("libSDL2.so");
+	if (sdl_lib != nullptr)
+	{
+		SDL_GetWindowBordersSize_ = (SDL_GetWindowBordersSizePtr)SDL_LoadFunction(sdl_lib,"SDL_GetWindowBordersSize");
+	}
+
 	// NOTE: Core profiles were added with GL 3.2, so there's no sense trying
 	// to set core 3.1 or 3.0. We could try a forward-compatible context
 	// instead, but that would be too restrictive (w.r.t. shaders).
@@ -227,6 +237,9 @@ SystemGLFrameBuffer::SystemGLFrameBuffer (void *, bool fullscreen)
 		);
 		if (Screen != NULL)
 		{
+			// enforce minimum size limit
+			SDL_SetWindowMinimumSize(Screen, MIN_WIDTH, MIN_HEIGHT);
+
 			GLContext = SDL_GL_CreateContext(Screen);
 			if (GLContext != NULL)
 			{
@@ -236,15 +249,16 @@ SystemGLFrameBuffer::SystemGLFrameBuffer (void *, bool fullscreen)
 
 				if (!fullscreen)
 				{
+					if (win_w >= MIN_WIDTH && win_h >= MIN_HEIGHT)
+					{
+						SDL_SetWindowSize(Screen, win_w, win_h);
+					}
+
 					if (win_x >= 0 && win_y >= 0)
 					{
 						SDL_SetWindowPosition(Screen, win_x, win_y);
 					}
 
-					if (win_h > 320 && win_w > 200)
-					{
-						SDL_SetWindowSize(Screen, win_w, win_h);
-					}
 				}
 
 				return;
@@ -258,6 +272,11 @@ SystemGLFrameBuffer::SystemGLFrameBuffer (void *, bool fullscreen)
 
 SystemGLFrameBuffer::~SystemGLFrameBuffer ()
 {
+	if (sdl_lib != nullptr)
+	{
+		SDL_UnloadObject(sdl_lib);
+	}
+
 	if (Screen)
 	{
 		ResetGammaTable();
@@ -326,6 +345,11 @@ void SystemGLFrameBuffer::SwapBuffers()
 void SystemGLFrameBuffer::ToggleFullscreen(bool yes)
 {
 	SDL_SetWindowFullscreen(Screen, yes ? SDL_WINDOW_FULLSCREEN_DESKTOP : 0);
+	if ( !yes )
+	{
+		fullscreen = false;
+		SetWindowSize(win_w, win_h);
+	}
 }
 
 int SystemGLFrameBuffer::GetClientWidth()
@@ -342,6 +366,39 @@ int SystemGLFrameBuffer::GetClientHeight()
 	return height;
 }
 
+void SystemGLFrameBuffer::SetWindowSize(int w, int h)
+{
+	if (w < MIN_WIDTH || h < MIN_HEIGHT)
+	{
+		w = MIN_WIDTH;
+		h = MIN_HEIGHT;
+	}
+	win_w = w;
+	win_h = h;
+	if ( fullscreen )
+	{
+		fullscreen = false;
+	}
+	else
+	{
+		win_maximized = false;
+		SDL_SetWindowSize(Screen, w, h);
+		SDL_SetWindowPosition(Screen, SDL_WINDOWPOS_CENTERED, SDL_WINDOWPOS_CENTERED);
+		SetSize(GetClientWidth(), GetClientHeight());
+		int x, y;
+		SDL_GetWindowPosition(Screen, &x, &y);
+		win_x = x;
+		win_y = y;
+	}
+}
+
+void SystemGLFrameBuffer::GetWindowBordersSize(int &top, int &left)
+{
+	if (SDL_GetWindowBordersSize_ != nullptr)
+	{
+		SDL_GetWindowBordersSize_(Screen, &top, &left, nullptr, nullptr);
+	}
+}
 
 void ProcessSDLWindowEvent(const SDL_WindowEvent &event)
 {
@@ -362,8 +419,10 @@ void ProcessSDLWindowEvent(const SDL_WindowEvent &event)
 	case SDL_WINDOWEVENT_MOVED:
 		if (!fullscreen)
 		{
-			win_x = event.data1;
-			win_y = event.data2;
+			int top = 0, left = 0;
+			static_cast<SystemGLFrameBuffer *>(screen)->GetWindowBordersSize(top,left);
+			win_x = event.data1-left;
+			win_y = event.data2-top;
 		}
 		break;
 
@@ -374,6 +433,14 @@ void ProcessSDLWindowEvent(const SDL_WindowEvent &event)
 			win_h = event.data2;
 		}
 		break;
+
+	case SDL_WINDOWEVENT_MAXIMIZED:
+		win_maximized = true;
+		break;
+
+	case SDL_WINDOWEVENT_RESTORED:
+		win_maximized = false;
+		break;
 	}
 }
 
@@ -391,3 +458,4 @@ void I_SetWindowTitle(const char* caption)
 		SDL_SetWindowTitle(window, default_caption);
 	}
 }
+