asked on

String in Windows message

Hello experts

I know how to send message to the system.
It looks like:

PostMessage(MyParams.HandleToForm, WM_THREAD_COMPLETE, LInteger0,
LInteger1);

Where I have handle to the form with procedure, name of the procedure and two integer parameters.

Question:

How can I pass parameter of String type?

Thank you

panJames

Thommy

Message Handling in Delphi
http://about-delphi.blogspot.com/2008/08/message-handling-in-delphi.html

jimyX

You can do something like this:

Str : String;

PostMessage(MyParams.HandleToForm, WM_THREAD_COMPLETE, @Str, LInteger1);

jimyX

That one will not work. But this will:

Str:string;
A : Integer;

Str := 'test';
A := GlobalAddAtom(Pchar(Str));
PostMessage(MyParams.HandleToForm, WM_THREAD_COMPLETE, iAtom, LInteger1);

jimyX

Str:string;
A : Integer;

Str := 'test';
A := GlobalAddAtom(Pchar(Str));
PostMessage(MyParams.HandleToForm, WM_THREAD_COMPLETE, A, length(Str));

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jimyX

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Russell Libby

Just keep the following rules in mind when passing strings (or any pointers, eg objects, etc):

- If you PostMessage with a string, you have to ensure the pointer (string) does not go out of scope before the window processes the message. Not a recommended way of sending strings.
- If you are SendMessage(..) ing strings/pointers, you can do so without issues as long as the window handling the message exists within the process.
- If you are SendMessage(..) ing strings/pointers to a window that exists in another process, then you will need to use some form of IPC (WM_COPYDATA, atoms, etc) as the pointer you are passing needs to be mapped into the process space of the window handling the message.

Russell