The TMSFNCCombobox behaves wrong under Windows10 (Delphi 10.4, VCL+FMX).
So can the problem be reproduced:
Create a new project
Place a TMSFNCComboBox and an edit field on the form
Create a few entries (items) in the TMSFNCComboBox
Compile/start the project
Problem 1:
Open the TMSFNCComboBox to select an entry
Click in the edit field without making a selection
The TMSFNCComboBox remains open
Problem 2: (FMX only)
In an FMX project the selection list of the TMSFNCComboBox always remains visible, even if the program is minimized and e.g. the Internet Explorer is opened.
Problem 3:
When moving the window the selection list is always updated with a certain delay.
The video shows the incorrect behaviour.
The VLC media player has problems playing, best use the Windows Media Player. Since no MP4 attachments are possible, I have zipped the file. Error_FNCCombobox.zip (151.7 KB)
We fixed the issue for the csDropDownList style, but for the csDropDown style this is not possible to fix. In TTMSFNCComboBox the visible edit field needs to stay in focus and for that we need to force the popup to stay on top.
If the popup should disappear at a specific action (for example a button click) then you can use TTMSFNCComboBox.DropDown. You can check if the popup is opened with TMSFNCComboBox.Popup.IsOpen.