toplevel: force WS_CLIPCHILDREN style

not only for performance, but also at least the combo box has subtly
drawing bugs when the toplevel doesn't set this style

1 files changed, 7 insertions, 0 deletions

diff --git a/alf/alftoplevel.cpp b/alf/alftoplevel.cpp
index d54d4b3..2d2f52d 100644
--- a/alf/alftoplevel.cpp
+++ b/alf/alftoplevel.cpp
@@ -142,6 +142,13 @@ static LRESULT CALLBACK
 ALF_Toplevel_WindowProc(HWND hwnd, UINT msg, WPARAM wparam, LPARAM lparam)
 {
     if (msg == WM_CREATE) {
+        // fixup default window style flags: we always want WS_CLIPCHILDREN
+        LONG style = GetWindowLong(hwnd, GWL_STYLE);
+        if (!(style & WS_CLIPCHILDREN)) {
+            style |= WS_CLIPCHILDREN;
+            SetWindowLong(hwnd, GWL_STYLE, style);
+        }
+
         ALFToplevelPriv *priv = ALF_New(ALFToplevelPriv, 1);
         SetWindowLongPtr(hwnd, DLGWINDOWEXTRA, (LONG_PTR)priv);
         ALF_InitializeToplevelPriv(hwnd, priv);