Add exit confirmation dialog on ESC in main menu (#16164)

builtin/mainmenu/dlg_confirm_exit.lua

@@ -0,0 +1,54 @@
+-- Luanti
+-- Copyright (C) 2025 siliconsniffer
+-- SPDX-License-Identifier: LGPL-2.1-or-later
+
+
+local function exit_dialog_formspec()
+	local show_dialog = core.settings:get_bool("enable_esc_dialog", true)
+	local formspec = {
+		"formspec_version[10]" ..
+		"size[10,3.6]" ..
+		"style_type[label;font=bold]" ..
+		"style[btn_quit_confirm_yes;bgcolor=red]" ..
+		"label[0.5,0.5;" .. fgettext("Are you sure you want to quit?") .. "]" ..
+		"checkbox[0.5,1.4;cb_show_dialog;" .. fgettext("Always show this dialog.") .. ";" .. tostring(show_dialog) .. "]" ..
+		"button[0.5,2.3;3,0.8;btn_quit_confirm_cancel;" .. fgettext("Cancel") .. "]" ..
+		"button[6.5,2.3;3,0.8;btn_quit_confirm_yes;" .. fgettext("Quit") .. "]" ..
+		"set_focus[btn_quit_confirm_yes]"
+	}
+	return table.concat(formspec, "")
+end
+
+
+local function exit_dialog_buttonhandler(this, fields)
+	if fields.cb_show_dialog ~= nil then
+		core.settings:set_bool("enable_esc_dialog", core.is_yes(fields.cb_show_dialog))
+		return false
+	elseif fields.btn_quit_confirm_yes then
+		this:delete()
+		core.close()
+		return true
+	elseif fields.btn_quit_confirm_cancel then
+		this:delete()
+		this:show()
+		return true
+	end
+end
+
+
+local function event_handler(event)
+	if event == "DialogShow" then
+		mm_game_theme.set_engine(true) -- hide the menu header
+		return true
+	end
+	return false
+end
+
+
+function create_exit_dialog()
+	local retval = dialog_create("dlg_exit",
+		exit_dialog_formspec,
+		exit_dialog_buttonhandler,
+		event_handler)
+	return retval
+end