Copy/paste some code from Windows OSD to get SDL going again - sorry if this is dirty

src/osd/sdl/sdlmain.cpp

@@ -245,9 +245,8 @@ static void output_oslog(const running_machine &machine, const char *buffer)
 //============================================================
 
 sdl_osd_interface::sdl_osd_interface(sdl_options &options)
-: osd_common_t(options), m_options(options)
+: osd_common_t(options), m_options(options), m_watchdog(nullptr), m_sliders(nullptr)
 {
-	m_watchdog = NULL;
 }
 
 

src/osd/sdl/video.cpp

@@ -92,6 +92,15 @@ bool sdl_osd_interface::video_init()
 }
 
 
+//============================================================
+//  get_slider_list
+//============================================================
+
+slider_state *sdl_osd_interface::get_slider_list()
+{
+	return m_sliders;
+}
+
 //============================================================
 //  video_exit
 //============================================================

src/osd/sdl/window.cpp

@@ -285,6 +285,50 @@ static void sdlwindow_sync(void)
 }
 
 
+void sdl_osd_interface::update_slider_list()
+{
+	for (sdl_window_info *window = sdl_window_list; window != nullptr; window = window->m_next)
+	{
+		// check if any window has dirty sliders
+		if (&window->renderer() && window->renderer().sliders_dirty())
+		{
+			build_slider_list();
+			return;
+		}
+	}
+}
+
+void sdl_osd_interface::build_slider_list()
+{
+    m_sliders = nullptr;
+    slider_state* full_list = nullptr;
+    slider_state* curr = nullptr;
+	for (sdl_window_info *window = sdl_window_list; window != nullptr; window = window->m_next)
+	{
+		// take the sliders of the first window
+        slider_state* window_sliders = window->renderer().get_slider_list();
+        if (window_sliders == nullptr)
+        {
+            continue;
+        }
+
+        if (full_list == nullptr)
+        {
+            full_list = curr = window_sliders;
+        }
+        else
+        {
+            curr->next = window_sliders;
+        }
+
+        while (curr->next != nullptr) {
+            curr = curr->next;
+        }
+	}
+
+    m_sliders = full_list;
+}
+
 //============================================================
 //  sdlwindow_exit
 //  (main thread)