[PATCH v2 0/2] MR8702: user32/tests: Add more SendMessageCallbackA/W() tests with NULL callback.

[Zhiyi Zhang (＠zhiyi)]

For React Native.

--
  v2: win32u: Put the message in the queue when callback pointer is NULL and callback data is 1.
      user32/tests: Add more SendMessageCallbackA/W() tests with NULL callback.

https://gitlab.winehq.org/wine/wine/-/merge_requests/8702

[PATCH v2 1/2] user32/tests: Add more SendMessageCallbackA/W() tests with NULL callback.

[Zhiyi Zhang]

From: Zhiyi Zhang

The tests are mainly to show that SendMessageCallbackA/W() with NULL callback pointer and callback
data being 1 causes the message to be posted to the window, even when the window is created in the
same thread.
---
 dlls/user32/tests/msg.c | 68 ++++++++++++++++++++++++++++++++++++++++-
 1 file changed, 67 insertions(+), 1 deletion(-)

diff --git a/dlls/user32/tests/msg.c b/dlls/user32/tests/msg.c
index 80d900baa1c..24be627a78d 100644
--- a/dlls/user32/tests/msg.c
+++ b/dlls/user32/tests/msg.c
@@ -16499,16 +16499,82 @@ static void test_EndDialog(void)
     UnregisterClassA(cls.lpszClassName, cls.hInstance);
 }

+static const struct message WmUserSeq[] =
+{
+    { WM_USER, sent },
+    { 0 }
+};
+
 static void test_nullCallback(void)
 {
+    DWORD status;
     HWND hwnd;
+    BOOL ret;

hwnd = CreateWindowExA(0, "TestWindowClass", "Test overlapped", WS_OVERLAPPEDWINDOW,
                            100, 100, 200, 200, 0, 0, 0, NULL);
     ok (hwnd != 0, "Failed to create overlapped window\n");

-    SendMessageCallbackA(hwnd,WM_NULL,0,0,NULL,0);
+    /* NULL callback and data being 0 with SendMessageCallbackA() */
+    flush_sequence();
+    ret = SendMessageCallbackA(hwnd, WM_USER, 0, 0, NULL, 0);
+    ok(ret, "SendMessageCallbackA failed, error %ld.", GetLastError());
+    ok_sequence(WmUserSeq, "WM_USER with NULL callback", FALSE);
+
+    /* NULL callback and data being 0 with SendMessageCallbackW() */
+    flush_sequence();
+    ret = SendMessageCallbackW(hwnd, WM_USER, 0, 0, NULL, 0);
+    ok(ret, "SendMessageCallbackW failed, error %ld.", GetLastError());
+    ok_sequence(WmUserSeq, "WM_USER with NULL callback", FALSE);
+
+    /* NULL callback and data being 1 with SendMessageCallbackA(). The result suggests that the
+     * message is not directly sent to the window */
+    flush_sequence();
+    ret = SendMessageCallbackA(hwnd, WM_USER, 0, 0, NULL, 1);
+    ok(ret, "SendMessageCallbackA failed, error %ld.", GetLastError());
+    ok_sequence(WmEmptySeq, "WM_USER with NULL callback", TRUE);
     flush_events();
+    ok_sequence(WmUserSeq, "WM_USER with NULL callback after flushing events", TRUE);
+
+    /* NULL callback and data being 1 with SendMessageCallbackW(). The result suggests that the
+     * message is not directly sent to the window */
+    flush_sequence();
+    ret = SendMessageCallbackW(hwnd, WM_USER, 0, 0, NULL, 1);
+    ok(ret, "SendMessageCallbackW failed, error %ld.", GetLastError());
+    ok_sequence(WmEmptySeq, "WM_USER with NULL callback", TRUE);
+    flush_events();
+    ok_sequence(WmUserSeq, "WM_USER with NULL callback after flushing events", TRUE);
+
+    /* NULL callback and data being 2 with SendMessageCallbackA() */
+    flush_sequence();
+    ret = SendMessageCallbackA(hwnd, WM_USER, 0, 0, NULL, 2);
+    ok(ret, "SendMessageCallbackA failed, error %ld.", GetLastError());
+    ok_sequence(WmUserSeq, "WM_USER with NULL callback", FALSE);
+
+    /* NULL callback and data being 2 with SendMessageCallbackW() */
+    flush_sequence();
+    ret = SendMessageCallbackW(hwnd, WM_USER, 0, 0, NULL, 2);
+    ok(ret, "SendMessageCallbackW failed, error %ld.", GetLastError());
+    ok_sequence(WmUserSeq, "WM_USER with NULL callback", FALSE);
+
+    /* Check the queue status after SendMessageCallbackA() with NULL callback and data being 1 */
+    flush_events();
+    ret = SendMessageCallbackA(hwnd, WM_USER, 0, 0, NULL, 1);
+    ok(ret, "SendMessageCallbackA failed, error %ld.", GetLastError());
+    status = GetQueueStatus(QS_ALLINPUT);
+    todo_wine
+    ok(HIWORD(status) & QS_SENDMESSAGE && LOWORD(status) & QS_SENDMESSAGE,
+       "Got unexpected status %#lx.\n", status);
+
+    /* Check the queue status after SendMessageCallbackW() with NULL callback and data being 1 */
+    flush_events();
+    ret = SendMessageCallbackW(hwnd, WM_USER, 0, 0, NULL, 1);
+    ok(ret, "SendMessageCallbackW failed, error %ld.", GetLastError());
+    status = GetQueueStatus(QS_ALLINPUT);
+    todo_wine
+    ok(HIWORD(status) & QS_SENDMESSAGE && LOWORD(status) & QS_SENDMESSAGE,
+       "Got unexpected status %#lx.\n", status);
+
     DestroyWindow(hwnd);
 }

[PATCH v2 2/2] win32u: Put the message in the queue when callback pointer is NULL and callback data is 1.

[Zhiyi Zhang]

From: Zhiyi Zhang

This is an undocumented behavior needed by React Native apps, based on Nikolay's findings.
---
 dlls/user32/tests/msg.c | 10 ++++------
 dlls/win32u/message.c   |  4 +++-
 2 files changed, 7 insertions(+), 7 deletions(-)

diff --git a/dlls/user32/tests/msg.c b/dlls/user32/tests/msg.c
index 24be627a78d..696cf41505e 100644
--- a/dlls/user32/tests/msg.c
+++ b/dlls/user32/tests/msg.c
@@ -16532,18 +16532,18 @@ static void test_nullCallback(void)
     flush_sequence();
     ret = SendMessageCallbackA(hwnd, WM_USER, 0, 0, NULL, 1);
     ok(ret, "SendMessageCallbackA failed, error %ld.", GetLastError());
-    ok_sequence(WmEmptySeq, "WM_USER with NULL callback", TRUE);
+    ok_sequence(WmEmptySeq, "WM_USER with NULL callback", FALSE);
     flush_events();
-    ok_sequence(WmUserSeq, "WM_USER with NULL callback after flushing events", TRUE);
+    ok_sequence(WmUserSeq, "WM_USER with NULL callback after flushing events", FALSE);

/* NULL callback and data being 1 with SendMessageCallbackW(). The result suggests that the
      * message is not directly sent to the window */
     flush_sequence();
     ret = SendMessageCallbackW(hwnd, WM_USER, 0, 0, NULL, 1);
     ok(ret, "SendMessageCallbackW failed, error %ld.", GetLastError());
-    ok_sequence(WmEmptySeq, "WM_USER with NULL callback", TRUE);
+    ok_sequence(WmEmptySeq, "WM_USER with NULL callback", FALSE);
     flush_events();
-    ok_sequence(WmUserSeq, "WM_USER with NULL callback after flushing events", TRUE);
+    ok_sequence(WmUserSeq, "WM_USER with NULL callback after flushing events", FALSE);

/* NULL callback and data being 2 with SendMessageCallbackA() */
     flush_sequence();
@@ -16562,7 +16562,6 @@ static void test_nullCallback(void)
     ret = SendMessageCallbackA(hwnd, WM_USER, 0, 0, NULL, 1);
     ok(ret, "SendMessageCallbackA failed, error %ld.", GetLastError());
     status = GetQueueStatus(QS_ALLINPUT);
-    todo_wine
     ok(HIWORD(status) & QS_SENDMESSAGE && LOWORD(status) & QS_SENDMESSAGE,
        "Got unexpected status %#lx.\n", status);

@@ -16571,7 +16570,6 @@ static void test_nullCallback(void)
     ret = SendMessageCallbackW(hwnd, WM_USER, 0, 0, NULL, 1);
     ok(ret, "SendMessageCallbackW failed, error %ld.", GetLastError());
     status = GetQueueStatus(QS_ALLINPUT);
-    todo_wine
     ok(HIWORD(status) & QS_SENDMESSAGE && LOWORD(status) & QS_SENDMESSAGE,
        "Got unexpected status %#lx.\n", status);

diff --git a/dlls/win32u/message.c b/dlls/win32u/message.c
index 2a824dbdab3..e64e8213f93 100644
--- a/dlls/win32u/message.c
+++ b/dlls/win32u/message.c
@@ -4189,7 +4189,9 @@ static BOOL process_message( struct send_message_info *info, DWORD_PTR *res_ptr,
     thread_info->msg_source = msg_source_unavailable;
     spy_enter_message( SPY_SENDMESSAGE, info->hwnd, info->msg, info->wparam, info->lparam );

-    if (info->dest_tid != GetCurrentThreadId())
+    if (info->dest_tid != GetCurrentThreadId() ||
+        /* undocumented behavior when callback pointer is NULL and data is 1. See test_nullCallback(). */
+        (info->type == MSG_CALLBACK && !info->callback && info->data == 1))
     {
         if (dest_pid != GetCurrentProcessId() && (info->type == MSG_ASCII || info->type == MSG_UNICODE))
             info->type = MSG_OTHER_PROCESS;

[Zhiyi Zhang (＠zhiyi)]

On Mon Aug  4 09:07:57 2025 +0000, Dmitry Timoshkov wrote:
> The queue status would confirm that the message is supposed to be posted
> and not sent.

Thanks. I've added tests for the queue status.

[Dmitry Timoshkov (＠dmitry)]

On Mon Aug  4 09:14:13 2025 +0000, Zhiyi Zhang wrote:
> Thanks. I've added tests for the queue status.

There's no need to add another copy of SendMessageCallback() tests just for checking the queue status.