Fixed pick_best_mode in both d3d and ddraw cases to manually extract

refresh information from the device's inline_config, since this is
done before the screen devices are start. Fixes 01491: switchres 
causes Exception at EIP=009413BF: ACCESS VIOLATION.

Also, fixed render_target_get_minimum_size() to return nominal values
if no screens are found.

src/emu/render.c

@@ -1405,6 +1405,7 @@ void render_target_compute_visible_area(render_target *target, INT32 target_widt
 void render_target_get_minimum_size(render_target *target, INT32 *minwidth, INT32 *minheight)
 {
 	float maxxscale = 1.0f, maxyscale = 1.0f;
+	int screens_considered = 0;
 	int layer;
 
 	/* scan the current view for all screens */
@@ -1450,12 +1451,18 @@ void render_target_get_minimum_size(render_target *target, INT32 *minwidth, INT3
 				}
 
 				/* pick the greater */
-				if (xscale > maxxscale)
+				maxxscale = MAX(xscale, maxxscale);
-					maxxscale = xscale;
+				maxyscale = MAX(yscale, maxyscale);
-				if (yscale > maxyscale)
+				screens_considered++;
-					maxyscale = yscale;
 			}
 	}
+	
+	/* if there were no screens considered, pick a nominal default */
+	if (screens_considered == 0)
+	{
+		maxxscale = 640.0f;
+		maxyscale = 480.0f;
+	}
 
 	/* round up */
 	if (minwidth != NULL)

src/osd/windows/drawd3d.c

@@ -1238,7 +1238,8 @@ static int get_adapter_for_monitor(d3d_info *d3d, win_monitor_info *monitor)
 
 static void pick_best_mode(win_window_info *window)
 {
-	double target_refresh = ATTOSECONDS_TO_HZ(video_screen_get_frame_period(Machine->primary_screen).attoseconds);
+	const device_config *primary_screen = video_screen_first(Machine->config);
+	double target_refresh = 60.0;
 	INT32 target_width, target_height;
 	d3d_info *d3d = window->drawdata;
 	INT32 minwidth, minheight;
@@ -1246,6 +1247,13 @@ static void pick_best_mode(win_window_info *window)
 	int maxmodes;
 	int modenum;
 
+	// determine the refresh rate of the primary screen
+	if (primary_screen != NULL)
+	{
+		const screen_config *config = primary_screen->inline_config;
+		target_refresh = ATTOSECONDS_TO_HZ(config->refresh);
+	}
+
 	// determine the minimum width/height for the selected target
 	// note: technically we should not be calling this from an alternate window
 	// thread; however, it is only done during init time, and the init code on

src/osd/windows/drawdd.c

@@ -1291,6 +1291,7 @@ static HRESULT WINAPI enum_modes_callback(LPDDSURFACEDESC2 desc, LPVOID context)
 
 static void pick_best_mode(win_window_info *window)
 {
+	const device_config *primary_screen = video_screen_first(Machine->config);
 	dd_info *dd = window->drawdata;
 	mode_enum_info einfo;
 	HRESULT result;
@@ -1304,7 +1305,15 @@ static void pick_best_mode(win_window_info *window)
 	// use those as the target for now
 	einfo.target_width = einfo.minimum_width * MAX(1, video_config.prescale);
 	einfo.target_height = einfo.minimum_height * MAX(1, video_config.prescale);
-	einfo.target_refresh = ATTOSECONDS_TO_HZ(video_screen_get_frame_period(Machine->primary_screen).attoseconds);
+
+	// determine the refresh rate of the primary screen
+	einfo.target_refresh = 60.0;
+	if (primary_screen != NULL)
+	{
+		const screen_config *config = primary_screen->inline_config;
+		einfo.target_refresh = ATTOSECONDS_TO_HZ(config->refresh);
+	}
+	printf("Target refresh = %f\n", einfo.target_refresh);
 
 	// if we're not stretching, allow some slop on the minimum since we can handle it
 	if (!video_config.hwstretch)