user: Don't bother checking the WS_VISIBLE style on the desktop window.

dlls/user/win.c

@@ -249,7 +249,6 @@ static HWND *list_window_children( HWND hwnd, ATOM atom, DWORD tid )
  *
  * Build an array of all parents of a given window, starting with
  * the immediate parent. The array must be freed with HeapFree.
- * Returns NULL if window is a top-level window.
  */
 static HWND *list_window_parents( HWND hwnd )
 {
@@ -2611,14 +2610,17 @@ BOOL WINAPI IsChild( HWND parent, HWND child )
 BOOL WINAPI IsWindowVisible( HWND hwnd )
 {
     HWND *list;
-    BOOL retval;
+    BOOL retval = TRUE;
     int i;
 
     if (!(GetWindowLongW( hwnd, GWL_STYLE ) & WS_VISIBLE)) return FALSE;
     if (!(list = list_window_parents( hwnd ))) return TRUE;
-    for (i = 0; list[i]; i++)
-        if (!(GetWindowLongW( list[i], GWL_STYLE ) & WS_VISIBLE)) break;
-    retval = !list[i];
+    if (list[0] && list[1])  /* desktop window is considered always visible so we don't check it */
+    {
+        for (i = 0; list[i+1]; i++)
+            if (!(GetWindowLongW( list[i], GWL_STYLE ) & WS_VISIBLE)) break;
+        retval = !list[i+1];
+    }
     HeapFree( GetProcessHeap(), 0, list );
     return retval;
 }
@@ -2634,7 +2636,7 @@ BOOL WINAPI IsWindowVisible( HWND hwnd )
 BOOL WIN_IsWindowDrawable( HWND hwnd, BOOL icon )
 {
     HWND *list;
-    BOOL retval;
+    BOOL retval = TRUE;
     int i;
     LONG style = GetWindowLongW( hwnd, GWL_STYLE );
 
@@ -2642,10 +2644,13 @@ BOOL WIN_IsWindowDrawable( HWND hwnd, BOOL icon )
     if ((style & WS_MINIMIZE) && icon && GetClassLongPtrW( hwnd, GCLP_HICON ))  return FALSE;
 
     if (!(list = list_window_parents( hwnd ))) return TRUE;
-    for (i = 0; list[i]; i++)
-        if ((GetWindowLongW( list[i], GWL_STYLE ) & (WS_VISIBLE|WS_MINIMIZE)) != WS_VISIBLE)
-            break;
-    retval = !list[i];
+    if (list[0] && list[1])  /* desktop window is considered always visible so we don't check it */
+    {
+        for (i = 0; list[i+1]; i++)
+            if ((GetWindowLongW( list[i], GWL_STYLE ) & (WS_VISIBLE|WS_MINIMIZE)) != WS_VISIBLE)
+                break;
+        retval = !list[i+1];
+    }
     HeapFree( GetProcessHeap(), 0, list );
     return retval;
 }