From 257c0b8cd7b9ef7138c69db5759df86b072f49bd Mon Sep 17 00:00:00 2001
From: sid <sidyhe@hotmail.com>
Date: Tue, 8 Aug 2023 12:36:30 +0800
Subject: [PATCH] feature: user defined GetMessage on Windows

---
 include/SDL_system.h                  |  8 ++++++++
 src/video/windows/SDL_windowsevents.c | 23 +++++++++++++++++++++--
 2 files changed, 29 insertions(+), 2 deletions(-)

diff --git a/include/SDL_system.h b/include/SDL_system.h
index 4b7eaddcc0..05b25a410f 100644
--- a/include/SDL_system.h
+++ b/include/SDL_system.h
@@ -55,6 +55,14 @@ typedef void (SDLCALL * SDL_WindowsMessageHook)(void *userdata, void *hWnd, unsi
  */
 extern DECLSPEC void SDLCALL SDL_SetWindowsMessageHook(SDL_WindowsMessageHook callback, void *userdata);
 
+// the return value is BOOL
+typedef int(SDLCALL *SDL_WindowsGetMessageImpl)(void *userdata, void *lpMsg, void *hWnd, unsigned int wMsgFilterMin, unsigned int wMsgFilterMax);
+
+/**
+ * Set a GetMessage implement, for blocking etc.
+ */
+extern DECLSPEC void SDLCALL SDL_SetWindowsGetMessageImpl(SDL_WindowsGetMessageImpl callback, void *userdata);
+
 #endif /* defined(__WIN32__) || defined(__GDK__) */
 
 #if defined(__WIN32__) || defined(__WINGDK__)
diff --git a/src/video/windows/SDL_windowsevents.c b/src/video/windows/SDL_windowsevents.c
index 180c1a8eb8..b44e025955 100644
--- a/src/video/windows/SDL_windowsevents.c
+++ b/src/video/windows/SDL_windowsevents.c
@@ -1767,6 +1767,25 @@ void SDL_SetWindowsMessageHook(SDL_WindowsMessageHook callback, void *userdata)
     g_WindowsMessageHookData = userdata;
 }
 
+// A user implement API: GetMessage
+static SDL_WindowsGetMessageImpl g_WindowsGetMessageImpl = NULL;
+static void *g_WindowsGetMessageImplData = NULL;
+
+void SDLCALL SDL_SetWindowsGetMessageImpl(SDL_WindowsGetMessageImpl callback, void* userdata)
+{
+    g_WindowsGetMessageImpl = callback;
+    g_WindowsGetMessageImplData = userdata;
+}
+
+static BOOL GetMessageImpl(LPMSG lpMsg, HWND hWnd, UINT wMsgFilterMin, UINT wMsgFilterMax)
+{
+    if (g_WindowsGetMessageImpl)
+    {
+        return g_WindowsGetMessageImpl(g_WindowsGetMessageImplData, lpMsg, hWnd, wMsgFilterMin, wMsgFilterMax);
+    }
+    return GetMessage(lpMsg, hWnd, wMsgFilterMin, wMsgFilterMax);
+}
+
 int WIN_WaitEventTimeout(_THIS, int timeout)
 {
     MSG msg;
@@ -1775,12 +1794,12 @@ int WIN_WaitEventTimeout(_THIS, int timeout)
         UINT_PTR timer_id = 0;
         if (timeout > 0) {
             timer_id = SetTimer(NULL, 0, timeout, NULL);
-            message_result = GetMessage(&msg, 0, 0, 0);
+            message_result = GetMessageImpl(&msg, 0, 0, 0);
             KillTimer(NULL, timer_id);
         } else if (timeout == 0) {
             message_result = PeekMessage(&msg, NULL, 0, 0, PM_REMOVE);
         } else {
-            message_result = GetMessage(&msg, 0, 0, 0);
+            message_result = GetMessageImpl(&msg, 0, 0, 0);
         }
         if (message_result) {
             if (msg.message == WM_TIMER && msg.hwnd == NULL && msg.wParam == timer_id) {