MEGA65: adding option to disable mouse emulation

The problem: Xemu user may leave mouse grab mode to do something with
their mouse. To avoid bothering the mouse-aware MEGA65 program running,
I returned zero for relative mouse position change in this case. However
that can cause problems with certain programs which are not mouse based
and expecting $FF if mouse is not there.

Author: lgblgblgb

targets/mega65/configdb.c

@@ -114,6 +114,7 @@ static const struct xemutools_configdef_switch_st switch_options[] = {
 	{ "matrixstart", "Start with matrix-mode activated", &configdb.matrixstart },
 	{ "matrixdisable", "Disable the matrix hotkey", &configdb.matrixdisable },
 	{ "ramcheckread", "Enabled warnings on reading unwritten memory (first 126K only)", &configdb.ramcheckread },
+	{ "nomouseemu", "Disable mouse emulation", &configdb.nomouseemu },
 	{ NULL }
 };
 

targets/mega65/configdb.h

@@ -115,6 +115,7 @@ struct configdb_st {
 	int	ramcheckread;
 	char	*init_attic;
 	int	joyport;
+	int	nomouseemu;
 };
 
 extern struct configdb_st configdb;

targets/mega65/input_devices.c

@@ -1,6 +1,6 @@
 /* A work-in-progess MEGA65 (Commodore-65 clone origins) emulator
    Part of the Xemu project, please visit: https://github.com/lgblgblgb/xemu
-   Copyright (C)2016-2023 LGB (Gábor Lénárt) <[email protected]>
+   Copyright (C)2016-2024 LGB (Gábor Lénárt) <[email protected]>
 
 This program is free software; you can redistribute it and/or modify
 it under the terms of the GNU General Public License as published by
@@ -519,9 +519,15 @@ int emu_callback_key ( int pos, SDL_Scancode key, int pressed, int handled )
 		if (pos == RESTORE_KEY_POS)
 			restore_is_held = 0;
 		if (pos == -2 && key == 0) {	// special case pos = -2, key = 0, handled = mouse button (which?) and release event!
-			if ((handled == SDL_BUTTON_LEFT) && set_mouse_grab(SDL_TRUE, 0)) {
-				OSD(-1, -1, " Mouse grab activated. Press \n both SHIFTs together to cancel.");
-				DEBUGPRINT("UI: mouse grab activated" NL);
+			if ((handled == SDL_BUTTON_LEFT)) {
+				if (configdb.nomouseemu) {
+					OSD(-1, -1, "Mouse emulation is disabled.\nCannot enter mouse grab mode.");
+				} else {
+					if (set_mouse_grab(SDL_TRUE, 0)) {
+						OSD(-1, -1, "Mouse grab activated. Press\nboth SHIFTs together to cancel.");
+						DEBUGPRINT("UI: mouse grab activated" NL);
+					}
+				}
 			}
 			if (handled == SDL_BUTTON_RIGHT) {
 				ui_enter();
@@ -534,26 +540,32 @@ int emu_callback_key ( int pos, SDL_Scancode key, int pressed, int handled )
 
 Uint8 get_mouse_x_via_sid ( void )
 {
-	static Uint8 result = 0;
 	if (is_mouse_grab()) {
+		static Uint8 result = 0;
 		static int mouse_x = 0;
 		mouse_x = (mouse_x + (hid_read_mouse_rel_x(-23, 23) / 3)) & 0x3F;
 		DEBUG("MOUSE: X is %d, result byte is %d" NL, mouse_x, result);
 		result = mouse_x << 1;
+		return result;
 	}
+	const Uint8 result = configdb.nomouseemu ? 0xFF : 0x00;
+	DEBUG("MOUSE: X query without mouse-grab is $%02X" NL, result);
 	return result;
 }
 
 
 Uint8 get_mouse_y_via_sid ( void )
 {
-	static Uint8 result = 0;
 	if (is_mouse_grab()) {
+		static Uint8 result = 0;
 		static int mouse_y = 0;
 		mouse_y = (mouse_y - (hid_read_mouse_rel_y(-23, 23) / 3)) & 0x3F;
 		DEBUG("MOUSE: Y is %d, result byte is %d" NL, mouse_y, result);
 		result = mouse_y << 1;
+		return result;
 	}
+	const Uint8 result = configdb.nomouseemu ? 0xFF : 0x00;
+	DEBUG("MOUSE: Y query without mouse-grab is $%02X" NL, result);
 	return result;
 }
 

targets/mega65/ui.c

@@ -862,8 +862,10 @@ static const struct menu_st menu_reset[] = {
 	{ NULL }
 };
 static const struct menu_st menu_inputdevices[] = {
-	{ "Enable mouse grab + emu",	XEMUGUI_MENUID_CALLABLE |
+	{ "Enable mouse grab",		XEMUGUI_MENUID_CALLABLE |
 					XEMUGUI_MENUFLAG_QUERYBACK,	xemugui_cb_set_mouse_grab, NULL },
+	{ "Disable mouse emulation",	XEMUGUI_MENUID_CALLABLE |
+					XEMUGUI_MENUFLAG_QUERYBACK,	xemugui_cb_toggle_int, (void*)&configdb.nomouseemu },
 	{ "Use OSD key debugger",	XEMUGUI_MENUID_CALLABLE |
 					XEMUGUI_MENUFLAG_QUERYBACK,	xemugui_cb_osd_key_debugger, NULL },
 	{ "Cursor keys as joystick",	XEMUGUI_MENUID_CALLABLE |