win32u: Check GUID_NULL display device if desktop atom is missing.

When using nulldrv, there's no module to call __wine_set_user_driver and the user driver is still lazy_load_driver when get_display_driver gets called during desktop windows creation. Then, load_desktop_driver fails as it cannot find the not-yet-created desktop window atom, and fails later explorer.exe window creations such as the systray window. Other processes don't suffer from this as they wait for the desktop window to be fully created, and its atom will be eventually set. This change makes sure that we succeed in the case nulldrv was selected by explorer.exe, while still failing in case of error with another user driver as it would fail to open the right display device GUID.

win32u: Check GUID_NULL display device if desktop atom is missing.
9c22a5ea · Rémi Bernon · Alexandre Julliard · 992d60e1 · 9c22a5ea
Commit 9c22a5ea authored Mar 03, 2023 by Rémi Bernon Committed by Alexandre Julliard Mar 03, 2023
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Showing with 11 additions and 3 deletions

driver.c dlls/win32u/driver.c +11 -3

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--- a/dlls/win32u/driver.c
+++ b/dlls/win32u/driver.c
@@ -923,6 +923,8 @@ static const WCHAR guid_key_suffixW[] = {'}','\\','0','0','0','0'};
 static BOOL load_desktop_driver( HWND hwnd )
 {
+    static const WCHAR guid_nullW[] = {'0','0','0','0','0','0','0','0','-','0','0','0','0','-','0','0','0','0','-',
+                                       '0','0','0','0','-','0','0','0','0','0','0','0','0','0','0','0','0',0};
    WCHAR key[ARRAYSIZE(guid_key_prefixW) + 40 + ARRAYSIZE(guid_key_suffixW)], *ptr;
    char buf[4096];
    KEY_VALUE_PARTIAL_INFORMATION *info = (void *)buf;
@@ -946,9 +948,15 @@ static BOOL load_desktop_driver( HWND hwnd )
    memcpy( key, guid_key_prefixW, sizeof(guid_key_prefixW) );
    ptr = key + ARRAYSIZE(guid_key_prefixW);
    if (NtQueryInformationAtom( guid_atom, AtomBasicInformation, buf, sizeof(buf), NULL ))
-        return FALSE;
+    {
-    memcpy( ptr, abi->Name, abi->NameLength );
+        wcscpy( ptr, guid_nullW );
-    ptr += abi->NameLength / sizeof(WCHAR);
+        ptr += ARRAY_SIZE(guid_nullW) - 1;
+    }
+    else
+    {
+        memcpy( ptr, abi->Name, abi->NameLength );
+        ptr += abi->NameLength / sizeof(WCHAR);
+    }
    memcpy( ptr, guid_key_suffixW, sizeof(guid_key_suffixW) );
    ptr += ARRAY_SIZE(guid_key_suffixW);