1 files changed, 37 insertions, 4 deletions
diff --git a/alf/alfcompat.cpp b/alf/alfcompat.cpp
index 3895545..8672bb8 100644
--- a/alf/alfcompat.cpp
+++ b/alf/alfcompat.cpp
@@ -260,11 +260,44 @@ ALF_Compat_fallbackIsThemeBackgroundPartiallyTransparent(HTHEME hTheme, int iPar
 static HRESULT WINAPI
 ALF_Compat_fallbackDrawThemeParentBackground(HWND hwnd, HDC hdc, RECT *prc)
 {
-    (void)hwnd;
-    (void)hdc;
-    (void)prc;
+    HWND parent = GetParent(hwnd);
+    if (!parent)
+        return E_NOTIMPL;
+
+    RECT rc;
+    if (prc) {
+        rc = *prc;
+    } else {
+        GetClientRect(hwnd, &rc);
+    }
+    MapWindowRect(hwnd, parent, &rc);
 
-    return E_NOTIMPL;
+    RECT childr;
+    GetClientRect(hwnd, &childr);
+    MapWindowRect(hwnd, parent, &childr);
+
+    POINT o;
+    OffsetViewportOrgEx(hdc, -childr.left, -childr.top, &o);
+
+    HRGN oldClipRgn = CreateRectRgn(0, 0, 0, 0);
+    if (!GetClipRgn(hdc, oldClipRgn)) {
+        DeleteObject(oldClipRgn);
+        oldClipRgn = NULL;
+    }
+
+    IntersectClipRect(hdc, rc.left, rc.top, rc.right, rc.bottom);
+
+    SendMessage(parent, WM_ERASEBKGND, (WPARAM)hdc, 0);
+    SendMessage(parent, WM_PRINTCLIENT, (WPARAM)hdc, (LPARAM)PRF_CLIENT);
+
+    SelectClipRgn(hdc, oldClipRgn);
+    if (oldClipRgn) {
+        DeleteObject(oldClipRgn);
+    }
+
+    SetViewportOrgEx(hdc, o.x, o.y, NULL);
+
+    return S_OK;
 }
 
 static HRESULT WINAPI