Added system.set_fullscreen() and core:toggle-fullscreen command

data/core/commands/core.lua

···
 local LogView = require "core.logview"
 
 
+local fullscreen = false
+
 command.add(nil, {
   ["core:quit"] = function()
     core.quit()
···
 
   ["core:force-quit"] = function()
     core.quit(true)
+  end,
+
+  ["core:toggle-fullscreen"] = function()
+    fullscreen = not fullscreen
+    system.set_fullscreen(fullscreen)
   end,
 
   ["core:reload-module"] = function()

data/core/keymap.lua

···
   ["ctrl+p"] = "core:open-project-file",
   ["ctrl+o"] = "core:open-file",
   ["ctrl+n"] = "core:new-doc",
+  ["alt+return"] = "core:toggle-fullscreen",
 
   ["alt+shift+j"] = "root:split-left",
   ["alt+shift+l"] = "root:split-right",

src/api/system.c

···
 #include <SDL2/SDL.h>
 #include <ctype.h>
 #include <dirent.h>
+#include <stdbool.h>
 #include <sys/stat.h>
 #include "api.h"
 #ifdef _WIN32
···
 }
 
 
+static int f_set_fullscreen(lua_State *L) {
+  luaL_checkany(L, 1);
+  bool b = lua_toboolean(L, 1);
+  SDL_SetWindowFullscreen(window, b ? SDL_WINDOW_FULLSCREEN_DESKTOP : 0);
+  return 0;
+}
+
+
 static int f_window_has_focus(lua_State *L) {
   unsigned flags = SDL_GetWindowFlags(window);
   lua_pushboolean(L, flags & SDL_WINDOW_INPUT_FOCUS);
···
   { "poll_event",          f_poll_event          },
   { "set_cursor",          f_set_cursor          },
   { "set_window_title",    f_set_window_title    },
+  { "set_fullscreen",      f_set_fullscreen      },
   { "window_has_focus",    f_window_has_focus    },
   { "show_confirm_dialog", f_show_confirm_dialog },
   { "list_dir",            f_list_dir            },