MEGA65: preliminary 'show scanlines' feature

* New CLI options (and config file keys):
	* -showscanlines: show scanlines with V200 modes
	* -allowscanlines: allow user programs to modify "show scanlines" setting
* New GUI menu sub-menu: show scanlines / allow user programs to modify
	(in the Display menu)

Warning, preliminary and crude! Not considered as final in any means!
Not enabled by default (use CLI options or config file, or enable
it with the GUI, as mentioned above).

targets/mega65/configdb.c

@@ -107,6 +107,8 @@ static const struct xemutools_configdef_switch_st switch_options[] = {
 	{ "noopl3", "Disables OPL3 emulation", &configdb.noopl3 },
 	{ "lockvideostd", "Lock video standard (programs cannot change it)", &configdb.lock_videostd },
 	{ "curskeyjoy", "Cursor keys as joystick [makes your emulator unsable to move cursor in BASIC/etc!]", &hid_joy_on_cursor_keys },
+	{ "showscanlines", "Show scanlines in V200 modes", &configdb.show_scanlines },
+	{ "allowscanlines", "Allow user programs to control scanline visibility", &configdb.allow_scanlines },
 	{ NULL }
 };
 

targets/mega65/configdb.h

@@ -72,6 +72,8 @@ struct configdb_st {
 	char	*selectedgui;
 	int	lock_videostd;
 	int	videostd;
+	int	show_scanlines;
+	int	allow_scanlines;
 	int	fullborders;
 	int	hdosvirt;
 	int	show_drive_led;

targets/mega65/ui.c

@@ -644,6 +644,13 @@ static void ui_cb_displayenable ( const struct menu_st *m, int *query )
 /**** MENU SYSTEM ****/
 
 
+static const struct menu_st menu_show_scanlines[] = {
+	{ "Disallow change by programs",XEMUGUI_MENUID_CALLABLE | XEMUGUI_MENUFLAG_SEPARATOR |
+					XEMUGUI_MENUFLAG_QUERYBACK,	xemugui_cb_toggle_int_inverted, (void*)&configdb.allow_scanlines },
+	{ "Show scanlines",		XEMUGUI_MENUID_CALLABLE |
+					XEMUGUI_MENUFLAG_QUERYBACK,	xemugui_cb_toggle_int, (void*)&configdb.show_scanlines },
+	{ NULL }
+};
 static const struct menu_st menu_video_standard[] = {
 	{ "Disallow change by programs",XEMUGUI_MENUID_CALLABLE | XEMUGUI_MENUFLAG_SEPARATOR |
 					XEMUGUI_MENUFLAG_QUERYBACK,	ui_cb_video_standard_disallow_change, NULL },
@@ -681,6 +688,7 @@ static const struct menu_st menu_display[] = {
 	{ "Render scale quality",	XEMUGUI_MENUID_SUBMENU,		NULL, menu_render_scale_quality },
 	{ "Window size / fullscreen",	XEMUGUI_MENUID_SUBMENU,		NULL, menu_window_size },
 	{ "Video standard",		XEMUGUI_MENUID_SUBMENU,		NULL, menu_video_standard },
+	{ "Show scanlines at V200",	XEMUGUI_MENUID_SUBMENU,		NULL, menu_show_scanlines },
 	{ "Show full borders",		XEMUGUI_MENUID_CALLABLE |
 					XEMUGUI_MENUFLAG_QUERYBACK,	ui_cb_fullborders, NULL },
 	{ "Show drive LED",		XEMUGUI_MENUID_CALLABLE |

targets/mega65/vic4.c

@@ -722,6 +722,8 @@ void vic_write_reg ( unsigned int addr, Uint8 data )
 		CASE_VIC_4(0x54):
 			vic_registers[0x54] = data;	// we need this work-around, since reg-write happens _after_ this switch statement, but machine_set_speed above needs it ...
 			machine_set_speed(0);
+			if (configdb.allow_scanlines && !in_hypervisor)	// FIXME: this is "do now allow to alter show-scanline setting by hypervisor"
+				configdb.show_scanlines = !!(data & 32);
 			return;				// since we DID the write, it's OK to return here and not using "break"
 		CASE_VIC_4(0x55): CASE_VIC_4(0x56): CASE_VIC_4(0x57): break;
 		CASE_VIC_4(0x58): CASE_VIC_4(0x59):
@@ -1555,10 +1557,13 @@ int vic4_render_scanline ( void )
 	// FIXME: is this really correct? ie even sprites cannot be set to Y pos finer than V200 or ...
 	// ... having resolution finer than V200 with some "VIC-IV magic"?
 	if (!EFFECTIVE_V400 && (ycounter & 1)) {
-		//for (int i = 0; i < TEXTURE_WIDTH; i++, current_pixel++)
-		//	*current_pixel = /* user_scanlines_setting ? 0 : */ *(current_pixel - TEXTURE_WIDTH);
-		memcpy(current_pixel, current_pixel - TEXTURE_WIDTH, TEXTURE_WIDTH * 4);
-		current_pixel += TEXTURE_WIDTH;
+		if (XEMU_UNLIKELY(configdb.show_scanlines)) {
+			for (int i = 0; i < TEXTURE_WIDTH; i++, current_pixel++)
+				*current_pixel = ((*(current_pixel - TEXTURE_WIDTH) >> 1) & 0x7F7F7F7FU) | black_colour;	// "| black_colour" is used to correct the messed-up alpha channel to $FF
+		} else {
+			memcpy(current_pixel, current_pixel - TEXTURE_WIDTH, TEXTURE_WIDTH * 4);
+			current_pixel += TEXTURE_WIDTH;
+		}
 	} else {
 		// Top and bottom borders
 		if (ycounter < BORDER_Y_TOP || ycounter >= BORDER_Y_BOTTOM || !REG_DISPLAYENABLE) {