Question: I am creating an MDI application and I would like to put my child window inside of a dll. How would I accomplish this?
Answer: Many times in an MDI applications the developer would like to place
the children inside of a dynamically linked library. A problem arises
when trying to do this with a Borland VCL DLL. The problem is that a VCL
DLL has a TApplication class that is different then the TApplication
class of the calling application. When this occurs the MDI Child checks
its TApplication class for the Parent window and none is found. Of
course none is found because the TApplication class that has the parent
is in the calling application not the DLL. So to get around this it is
recommended that one uses a Package instead of a DLL. To do this simply
create a package instead of a DLL and then add your MDI Child to the
package. Treat the package just like you treat a DLL.
For a more in-depth example of doing this take a look at code example