TScreen

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Share memory among several instances of a DLL

TScreen

5 comments. Current rating: 5 stars

(3 votes). Leave comments and/ or rate it.

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:

const
  SavedApplication : TApplication = nil;
  SavedScreen : TScreen = nil;

// export this procedure and call it after loading the DLL
procedure Init(anApplicationHandle, aScreenHandle: LongWord);
begin
  if not Assigned(SavedApplication) then
  begin
    SavedApplication := Application;
    Application := TApplication(anApplicationHandle);
  end;

  if not Assigned(SavedScreen) then
  begin
    // ....same...
  end;
end;

initialization

finalization
  if Assigned(SavedApplication) then
  begin
    Application := SavedApplication;
  end;

  if Assigned(SavedScreen) then
  begin
    // ....same.....
  end;
end.

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Comments:

2006-10-04, 01:50:39

anonymous from United States

Helps us geeks to build plugins

2006-12-16, 03:09:26

anonymous from China

Thanks

2007-11-26, 09:21:30

samdhunt@comcast.net from United States

My DLL errors on the reference to TApplication in the second line of your example.

const
SavedApplication : TApplication = nil;
SavedScreen : TScreen = nil;

I have tried several code examples using TApplication in my DLL and they all error.

I'd like to be able to create a form contained in a DLL from my EXE and set some form properties. I have succeeded in creating the form, but cannot set form properties because (from what I have read) my EXE and DLL don't share the same TApplication and TScreen.

Help!

Sam Hunt
Auburn, WA USA

2008-03-31, 16:45:34 (updated: 2008-03-31, 16:48:15)

anonymous

const
SavedApplication : TApplication = nil;
SavedScreen : TScreen = nil;

You can't assign a value to a constant variable like this.

Also ...

SavedApplication := Application;

won't work cause it's declared as constant.

2009-10-01, 06:59:03

anonymous from Italy

Thank you for explanation

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