问题
As per my previous question (Delphi 6 support for toolbar and menu icons with alpha channel transparency), we are updating a legacy application developed in Delphi 6 to support Windows Visual Themes by including a Manifest. This has worked well and we have the majority of controls adopting the Windows visual theme correctly.
However, we do have a problem with TDateTimePicker behaving in a slightly odd manner. We have the form colour set to white (RGB 255/255/255) and the input box for TDateTimePicker is not visible on the form until it is clicked into and has an entry in it. Please see screenshots below:
Changing the form colour to grey, we can see that the box is there when not selected, it just has no border drawn around it:
We have been unable to find a property that will change this behaviour. Can anyone shed some light on why this might be occurring, what property needs to be changed, or another method we could possibly use to resolve it?
来源：https://stackoverflow.com/questions/33304377/delphi-6-tdatetimepicker-windows-visual-theme-support-via-manifest