Author: Tomas Rutkauskas

TScreen, TApplication used in a DLL

Answer:

Each DLL in Delphi maintains its own instance of Application & Screen, your 
DLL-calling application should send the its own Application and Screen values to 
the DLL. The DLL should save and restore its original values.

You should put this code somewhere in your DLL and call the Init() function from 
your application:


1   const
2     SavedApplication: TApplication = nil;
3     SavedScreen: TScreen = nil;
4   
5     // export this procedure and call it after loading the DLL
6   
7   procedure Init(anApplicationHandle, aScreenHandle: LongWord);
8   begin
9     if not Assigned(SavedApplication) then
10    begin
11      SavedApplication := Application;
12      Application := TApplication(anApplicationHandle);
13    end;
14  
15    if not Assigned(SavedScreen) then
16    begin
17      // ....same...
18    end;
19  end;
20  
21  initialization
22  
23  finalization
24    if Assigned(SavedApplication) then
25    begin
26      Application := SavedApplication;
27    end;
28  
29    if Assigned(SavedScreen) then
30    begin
31      // ....same.....
32    end;
33  end.