BeginComboPreview: fix when part of preview rect is clipped by parent window. (#6501, #1658)

imgui_widgets.cpp

@@ -1829,7 +1829,7 @@ bool ImGui::BeginComboPreview()
     if (window->SkipItems || !(g.LastItemData.StatusFlags & ImGuiItemStatusFlags_Visible))
         return false;
     IM_ASSERT(g.LastItemData.Rect.Min.x == preview_data->PreviewRect.Min.x && g.LastItemData.Rect.Min.y == preview_data->PreviewRect.Min.y); // Didn't call after BeginCombo/EndCombo block or forgot to pass ImGuiComboFlags_CustomPreview flag?
-    if (!window->ClipRect.Contains(preview_data->PreviewRect)) // Narrower test (optional)
+    if (!window->ClipRect.Overlaps(preview_data->PreviewRect)) // Narrower test (optional)
         return false;
 
     // FIXME: This could be contained in a PushWorkRect() api