[UI] Loop thread to main thread WindowedAppContext

src/xenia/ui/windowed_app_context_win.cc

@@ -0,0 +1,130 @@
+/**
+ ******************************************************************************
+ * Xenia : Xbox 360 Emulator Research Project                                 *
+ ******************************************************************************
+ * Copyright 2021 Ben Vanik. All rights reserved.                             *
+ * Released under the BSD license - see LICENSE in the root for more details. *
+ ******************************************************************************
+ */
+
+#include "xenia/ui/windowed_app_context_win.h"
+
+#include <cstdlib>
+
+#include "xenia/base/platform_win.h"
+
+namespace xe {
+namespace ui {
+
+bool Win32WindowedAppContext::pending_functions_window_class_registered_;
+
+Win32WindowedAppContext::~Win32WindowedAppContext() {
+  if (pending_functions_hwnd_) {
+    DestroyWindow(pending_functions_hwnd_);
+  }
+}
+
+bool Win32WindowedAppContext::Initialize() {
+  // Logging possibly not initialized in this function yet.
+  // Create the message-only window for executing pending functions - using a
+  // window instead of executing them between iterations so non-main message
+  // loops, such as Windows modals, can execute pending functions too.
+  static const WCHAR kPendingFunctionsWindowClassName[] =
+      L"XeniaPendingFunctionsWindowClass";
+  if (!pending_functions_window_class_registered_) {
+    WNDCLASSEXW pending_functions_window_class = {};
+    pending_functions_window_class.cbSize =
+        sizeof(pending_functions_window_class);
+    pending_functions_window_class.lpfnWndProc = PendingFunctionsWndProc;
+    pending_functions_window_class.hInstance = hinstance_;
+    pending_functions_window_class.lpszClassName =
+        kPendingFunctionsWindowClassName;
+    if (!RegisterClassExW(&pending_functions_window_class)) {
+      return false;
+    }
+    pending_functions_window_class_registered_ = true;
+  }
+  pending_functions_hwnd_ = CreateWindowExW(
+      0, kPendingFunctionsWindowClassName, L"Xenia Pending Functions",
+      WS_OVERLAPPED, CW_USEDEFAULT, CW_USEDEFAULT, CW_USEDEFAULT, CW_USEDEFAULT,
+      HWND_MESSAGE, nullptr, hinstance_, this);
+  if (!pending_functions_hwnd_) {
+    return false;
+  }
+  return true;
+}
+
+void Win32WindowedAppContext::NotifyUILoopOfPendingFunctions() {
+  while (!PostMessageW(pending_functions_hwnd_,
+                       kPendingFunctionsWindowClassMessageExecute, 0, 0)) {
+    Sleep(1);
+  }
+}
+
+void Win32WindowedAppContext::PlatformQuitFromUIThread() {
+  // Send WM_QUIT to whichever loop happens to process it - may be the loop of a
+  // built-in modal window, which is unaware of HasQuitFromUIThread, don't let
+  // it delay quitting indefinitely.
+  PostQuitMessage(EXIT_SUCCESS);
+}
+
+int Win32WindowedAppContext::RunMainMessageLoop() {
+  int result = EXIT_SUCCESS;
+  MSG message;
+  // The HasQuitFromUIThread check is not absolutely required, but for
+  // additional safety in case WM_QUIT is not received for any reason.
+  while (!HasQuitFromUIThread()) {
+    BOOL message_result = GetMessageW(&message, nullptr, 0, 0);
+    if (message_result == 0 || message_result == -1) {
+      // WM_QUIT (0 - this is the primary message loop, no need to resend, also
+      // contains the result from PostQuitMessage in wParam) or an error
+      // (-1). Quitting the context will run the pending functions. Getting
+      // WM_QUIT doesn't imply that QuitFromUIThread has been called already, it
+      // may originate in some place other than PlatformQuitFromUIThread as
+      // well - call it to finish everything including the pending functions.
+      QuitFromUIThread();
+      result = message_result ? EXIT_FAILURE : int(message.wParam);
+      break;
+    }
+    TranslateMessage(&message);
+    DispatchMessageW(&message);
+  }
+  return result;
+}
+
+LRESULT CALLBACK Win32WindowedAppContext::PendingFunctionsWndProc(
+    HWND hwnd, UINT message, WPARAM wparam, LPARAM lparam) {
+  if (message == WM_CLOSE) {
+    // Need the window for the entire context's lifetime, don't allow anything
+    // to close it.
+    return 0;
+  }
+  if (message == WM_NCCREATE) {
+    SetWindowLongPtrW(
+        hwnd, GWLP_USERDATA,
+        reinterpret_cast<LONG_PTR>(
+            reinterpret_cast<const CREATESTRUCTW*>(lparam)->lpCreateParams));
+  } else {
+    auto app_context = reinterpret_cast<Win32WindowedAppContext*>(
+        GetWindowLongPtrW(hwnd, GWLP_USERDATA));
+    if (app_context) {
+      switch (message) {
+        case WM_DESTROY:
+          // The message-only window owned by the context is being destroyed,
+          // thus the context won't be able to execute pending functions
+          // anymore - can't continue functioning normally.
+          app_context->QuitFromUIThread();
+          break;
+        case kPendingFunctionsWindowClassMessageExecute:
+          app_context->ExecutePendingFunctionsFromUIThread();
+          break;
+        default:
+          break;
+      }
+    }
+  }
+  return DefWindowProcW(hwnd, message, wparam, lparam);
+}
+
+}  // namespace ui
+}  // namespace xe