[lua] Close stdin handle when we start running the GUI

src/app/app.cpp

@@ -267,9 +267,19 @@ int App::initialize(const AppOptions& options)
 
 #ifdef ENABLE_UI
   m_isGui = options.startUI() && !options.previewCLI();
+
+  // Notify the scripting engine that we're going to enter to GUI
+  // mode, this is useful so we can mark the stdin file handle as
+  // closed so no script can hang the program if it tries to read from
+  // stdin when the GUI is running.
+  #ifdef ENABLE_SCRIPTING
+    if (m_isGui)
+      m_engine->notifyRunningGui();
+  #endif
 #else
   m_isGui = false;
 #endif
+
   m_isShell = options.startShell();
   m_coreModules = std::make_unique<CoreModules>();
 

src/app/script/engine.cpp

@@ -536,6 +536,24 @@ void Engine::destroy()
   L = nullptr;
 }
 
+void Engine::notifyRunningGui()
+{
+  // Mark stdin file handle as closed so the following statements
+  // don't hang the program:
+  // - io.lines()
+  // - io.read('a')
+  // - io.stdin:read('a')
+  lua_getglobal(L, "io");
+  lua_getfield(L, -1, "stdin");
+
+  auto p = ((luaL_Stream*)luaL_checkudata(L, -1, LUA_FILEHANDLE));
+  ASSERT(p);
+  p->f = nullptr;
+  p->closef = nullptr;
+
+  lua_pop(L, 2);
+}
+
 void Engine::printLastResult()
 {
   m_printLastResult = true;

src/app/script/engine.h

@@ -1,5 +1,5 @@
 // Aseprite
-// Copyright (C) 2018-2023  Igara Studio S.A.
+// Copyright (C) 2018-2024  Igara Studio S.A.
 // Copyright (C) 2001-2018  David Capello
 //
 // This program is distributed under the terms of
@@ -97,6 +97,9 @@ namespace app {
       m_delegate = delegate;
     }
 
+    // Called if the GUI is going to be started.
+    void notifyRunningGui();
+
     void printLastResult();
     bool evalCode(const std::string& code,
                   const std::string& filename = std::string());