comctl32: TTM_ADDTOOLW must refuse to set a tooltip text to NULL.

dlls/comctl32/status.c

@@ -700,10 +700,12 @@ STATUSBAR_SetParts (STATUS_INFO *infoPtr, INT count, LPINT parts)
     if (infoPtr->hwndToolTip) {
 	INT nTipCount;
 	TTTOOLINFOW ti;
+	WCHAR wEmpty = 0;
 
 	ZeroMemory (&ti, sizeof(TTTOOLINFOW));
 	ti.cbSize = sizeof(TTTOOLINFOW);
 	ti.hwnd = infoPtr->Self;
+	ti.lpszText = &wEmpty;
 
 	nTipCount = SendMessageW (infoPtr->hwndToolTip, TTM_GETTOOLCOUNT, 0, 0);
 	if (nTipCount < infoPtr->numParts) {

dlls/comctl32/tests/tooltips.c

@@ -420,7 +420,7 @@ static void test_gettext(void)
     toolinfoW.lParam = 0xdeadbeef;
     GetClientRect(hwnd, &toolinfoW.rect);
     r = SendMessageW(hwnd, TTM_ADDTOOLW, 0, (LPARAM)&toolinfoW);
-    todo_wine ok(!r, "Adding the tool to the tooltip failed\n");
+    ok(!r, "Adding the tool to the tooltip succeeded!\n");
 
     if (0)  /* crashes on NT4 */
     {

dlls/comctl32/tooltips.c

@@ -1037,6 +1037,9 @@ TOOLTIPS_AddToolT (TOOLTIPS_INFO *infoPtr, const TTTOOLINFOW *ti, BOOL isW)
 	   infoPtr->hwndSelf, ti->hwnd, ti->uId,
 	   (ti->uFlags & TTF_IDISHWND) ? " TTF_IDISHWND" : "");
 
+    if (ti->cbSize >= TTTOOLINFOW_V2_SIZE && !ti->lpszText && isW)
+        return FALSE;
+
     if (infoPtr->uNumTools == 0) {
 	infoPtr->tools = Alloc (sizeof(TTTOOL_INFO));
 	toolPtr = infoPtr->tools;
@@ -1060,6 +1063,7 @@ TOOLTIPS_AddToolT (TOOLTIPS_INFO *infoPtr, const TTTOOLINFOW *ti, BOOL isW)
     toolPtr->rect   = ti->rect;
     toolPtr->hinst  = ti->hinst;
 
+    if (ti->cbSize >= TTTOOLINFOW_V1_SIZE) {
         if (IS_INTRESOURCE(ti->lpszText)) {
             TRACE("add string id %x\n", LOWORD(ti->lpszText));
             toolPtr->lpszText = ti->lpszText;
@@ -1082,6 +1086,7 @@ TOOLTIPS_AddToolT (TOOLTIPS_INFO *infoPtr, const TTTOOLINFOW *ti, BOOL isW)
                 MultiByteToWideChar(CP_ACP, 0, (LPSTR)ti->lpszText, -1, toolPtr->lpszText, len);
             }
         }
+    }
 
     if (ti->cbSize >= TTTOOLINFOW_V2_SIZE)
 	toolPtr->lParam = ti->lParam;

dlls/comctl32/trackbar.c

@@ -1526,10 +1526,12 @@ TRACKBAR_Create (HWND hwnd, const CREATESTRUCTW *lpcs)
 
     	if (infoPtr->hwndToolTip) {
             TTTOOLINFOW ti;
+            WCHAR wEmpty = 0;
             ZeroMemory (&ti, sizeof(ti));
             ti.cbSize   = sizeof(ti);
      	    ti.uFlags   = TTF_IDISHWND | TTF_TRACK | TTF_ABSOLUTE;
 	    ti.hwnd     = hwnd;
+            ti.lpszText = &wEmpty;
 
             SendMessageW (infoPtr->hwndToolTip, TTM_ADDTOOLW, 0, (LPARAM)&ti);
 	 }