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

[Zhiyi Zhang (＠zhiyi)]

For React Native.

[PATCH 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 message to be posted to window, even when the window is created in the same thread.
---
 dlls/user32/tests/msg.c | 39 ++++++++++++++++++++++++++++++++++++++-
 1 file changed, 38 insertions(+), 1 deletion(-)

diff --git a/dlls/user32/tests/msg.c b/dlls/user32/tests/msg.c
index 80d900baa1c..1c2d61c7781 100644
--- a/dlls/user32/tests/msg.c
+++ b/dlls/user32/tests/msg.c
@@ -16499,6 +16499,12 @@ static void test_EndDialog(void)
     UnregisterClassA(cls.lpszClassName, cls.hInstance);
 }

+static const struct message WmUserSeq[] =
+{
+    { WM_USER, sent },
+    { 0 }
+};
+
 static void test_nullCallback(void)
 {
     HWND hwnd;
@@ -16507,8 +16513,39 @@ static void test_nullCallback(void)
                            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 */
+    flush_sequence();
+    SendMessageCallbackA(hwnd, WM_USER, 0, 0, NULL, 0);
+    ok_sequence(WmUserSeq, "WM_USER with NULL callback", FALSE);
+
+    flush_sequence();
+    SendMessageCallbackW(hwnd, WM_USER, 0, 0, NULL, 0);
+    ok_sequence(WmUserSeq, "WM_USER with NULL callback", FALSE);
+
+    /* NULL callback and data being 1. The result suggests that the message is posted to the window */
+    flush_sequence();
+    SendMessageCallbackA(hwnd, WM_USER, 0, 0, NULL, 1);
+    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. The result suggests that the message is posted to the window */
+    flush_sequence();
+    SendMessageCallbackW(hwnd, WM_USER, 0, 0, NULL, 1);
+    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 */
+    flush_sequence();
+    SendMessageCallbackA(hwnd, WM_USER, 0, 0, NULL, 2);
+    ok_sequence(WmUserSeq, "WM_USER with NULL callback", FALSE);
+
+    /* NULL callback and data being 2 */
+    flush_sequence();
+    SendMessageCallbackW(hwnd, WM_USER, 0, 0, NULL, 2);
+    ok_sequence(WmUserSeq, "WM_USER with NULL callback", FALSE);
+
     DestroyWindow(hwnd);
 }

[PATCH 2/2] user32: Post message when callback pointer is NULL and callback data is 1 in SendMessageCallbackA/W().

[Zhiyi Zhang]

From: Zhiyi Zhang

This is an undocumented behavior needed by React Native apps, based on Nikolay's findings.
---
 dlls/user32/message.c   | 7 +++++++
 dlls/user32/tests/msg.c | 8 ++++----
 2 files changed, 11 insertions(+), 4 deletions(-)

diff --git a/dlls/user32/message.c b/dlls/user32/message.c
index 205d3e01c02..3b541959faf 100644
--- a/dlls/user32/message.c
+++ b/dlls/user32/message.c
@@ -640,6 +640,9 @@ BOOL WINAPI SendMessageCallbackA( HWND hwnd, UINT msg, WPARAM wparam, LPARAM lpa
 {
     struct send_message_callback_params params = { .callback = callback, .data = data };

+    if (!callback && data == 1)
+        return PostMessageA( hwnd, msg, wparam, lparam );
+
     if (!WIN_IsCurrentThread( hwnd ) && !map_wparam_AtoW( msg, &wparam, WMCHAR_MAP_SENDMESSAGE ))
         return FALSE;

@@ -654,6 +657,10 @@ BOOL WINAPI SendMessageCallbackW( HWND hwnd, UINT msg, WPARAM wparam, LPARAM lpa
                                   SENDASYNCPROC callback, ULONG_PTR data )
 {
     struct send_message_callback_params params = { .callback = callback, .data = data };
+
+    if (!callback && data == 1)
+        return PostMessageW( hwnd, msg, wparam, lparam );
+
     return NtUserMessageCall( hwnd, msg, wparam, lparam, &params, NtUserSendMessageCallback, FALSE );
 }

diff --git a/dlls/user32/tests/msg.c b/dlls/user32/tests/msg.c
index 1c2d61c7781..9089e96aa84 100644
--- a/dlls/user32/tests/msg.c
+++ b/dlls/user32/tests/msg.c
@@ -16525,16 +16525,16 @@ static void test_nullCallback(void)
     /* NULL callback and data being 1. The result suggests that the message is posted to the window */
     flush_sequence();
     SendMessageCallbackA(hwnd, WM_USER, 0, 0, NULL, 1);
-    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. The result suggests that the message is posted to the window */
     flush_sequence();
     SendMessageCallbackW(hwnd, WM_USER, 0, 0, NULL, 1);
-    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 */
     flush_sequence();

[Dmitry Timoshkov (＠dmitry)]

What's the reason for adding duplicate tests?

[Dmitry Timoshkov (＠dmitry)]

Also, it would be interesting to test the queue status.

[Zhiyi Zhang (＠zhiyi)]

On Mon Aug  4 07:36:35 2025 +0000, Dmitry Timoshkov wrote:
> What's the reason for adding duplicate tests?

Both SendMessageCallbackA() and SendMessageCallbackW() are being tested. The main purpose is to test an undocumented behavior, so we need to know that it's not limited only to the A/W() variant.

[Zhiyi Zhang (＠zhiyi)]

On Mon Aug  4 07:36:35 2025 +0000, Dmitry Timoshkov wrote:
> Also, it would be interesting to test the queue status.

Could you please elaborate on the queue status you would like me to test? I've added the message sequence tests.

[Dmitry Timoshkov (＠dmitry)]

On Mon Aug  4 07:36:35 2025 +0000, Zhiyi Zhang wrote:
> Could you please elaborate on the queue status you would like me to
> test? I've added the message sequence tests.

The queue status would confirm that the message is supposed to be posted and not sent.

[Dmitry Timoshkov (＠dmitry)]

On Mon Aug  4 07:36:34 2025 +0000, Zhiyi Zhang wrote:
> Both SendMessageCallbackA() and SendMessageCallbackW() are being tested.
> The main purpose is to test an undocumented behavior, so we need to know
> that it's not limited only to the A/W() variant.

Thanks. Probably a comment that clarifies that would be helpful.

[Dmitry Timoshkov (＠dmitry)]

Also it would be interesting to test return value of SendMessageCallback().