Solved

An Object with Handle

Posted on 1998-06-11
14
221 Views
Last Modified: 2013-11-23
Hi,

I need to create an object that recieves messages and perform some procedures according to this messages.
Is there a way to create an object with Handle, but not a subclass of TWinControl and not the DDE component,
meaning this object is derived directly from TObject?

Thanks,
Ronit
0
Comment
Question by:ronit051397
  • 5
  • 4
  • 3
  • +1
14 Comments
 
LVL 5

Expert Comment

by:inter
ID: 1352163
Hi ronit,
The thing that we should note here is that Windows only posts messages to handles associated with windows class or subclass. If you do not want to use TWinControl or else we should explicitely create a Window handle and associate its message callback with CreateWindow function. But this is virtually same as what TWinControl does. So why do you need such thing. May be we can use events rather than messages.
Regards, Igor
0
 
LVL 5

Expert Comment

by:JimBob091197
ID: 1352164
Hi

You can do the following:

constructor TMyObject.Create;
  inherited;
  FHandle := AllocateHWnd(WndProc);
end;

destructor TMyObject.Destroy;
begin
  DeallocateHWnd(FHandle);
  inherited;
end;

procedure TMyObject.WndProc(var AMsg: TMessage);
begin
  case Msg.Msg of
    WM_THIS:...;
    WM_THAT:...;
    else
      Msg.Result := DefWindowProc(FWindowHandle, Msg, wParam, lParam);
  end;
end;

This is a similar approach to TTimer (in ExtCtrls.pas).  I haven't tried it for a TObject, but it *should* work...

Cheers,
JB
0
 
LVL 5

Author Comment

by:ronit051397
ID: 1352165
Actually threads and processes have handles, as far as I know they can get messages and are not windows.
The DDE protocol is based on messages and it doesn't have to be related to a certain window, I mean, you can create a non windowed process and use DDE with it.
CreateWindow has something to do with visible stuff, But I am writing a non windowed "engine" that has to get messages from the system.
What I need is to Create an object and accociate a handle to it (maybe by CreateHandle or something), then to write methods that get certain messages and perform stuff.
Is it possible this way?
0
 
LVL 5

Expert Comment

by:JimBob091197
ID: 1352166
Oops...  change the WndProc to:

procedure TMyObject.WndProc(var Msg: TMessage);
begin
  case Msg.Msg of
    WM_THIS:...;
    WM_THAT:...;
    else
      Msg.Result := DefWindowProc(FWindowHandle, Msg.Msg, Msg.wParam, Msg.lParam);
  end;
end;

JB
0
 
LVL 5

Author Comment

by:ronit051397
ID: 1352167
JB, I didn't see your comment, I'll check it.
0
 
LVL 5

Author Comment

by:ronit051397
ID: 1352168
Thanks JB, it's working. If you post some answer i'll grade it.
0
 
LVL 3

Expert Comment

by:Matvey
ID: 1352169
Ronit, (some more) if you want your coponents to receive messages like top windows do, then see a component that ZifNab wrote - TCDEvents. You can find it in the Delphi pages or I can send it to you...

bosism@netvision.net.il
0
Is Your Active Directory as Secure as You Think?

More than 75% of all records are compromised because of the loss or theft of a privileged credential. Experts have been exploring Active Directory infrastructure to identify key threats and establish best practices for keeping data safe. Attend this month’s webinar to learn more.

 
LVL 5

Author Comment

by:ronit051397
ID: 1352170
Matvay, Please do:  ronith@cmr.co.il

Thanks,
Ronit
0
 
LVL 5

Expert Comment

by:JimBob091197
ID: 1352171
Ronit: before I post an answer I'll wait for you to check out Zif's component which Matvey mentioned.

JB
0
 
LVL 5

Expert Comment

by:inter
ID: 1352172
Hi,
Well, this is cooperation. You are all, soo nobble guys. You make EE distinctive with these actions.
(Excuse me for my excitement but it is not common to see such a discussion on the net these days)
Regards, Igor
0
 
LVL 3

Expert Comment

by:Matvey
ID: 1352173
Hi Igor!

It's been a long time...

Ronit, I sent you the component. It might not be the last ver, but still cool enough. -Enjoy

--Matvey
0
 
LVL 5

Author Comment

by:ronit051397
ID: 1352174
Thanks Matvey. I have checked the component, it's derived from TComponent and it opens and closes the CD Door (meaning Eject), nice to know that there is one.
Yes, it uses the procedures you have posted, JB.
But now we know that we can use these procedures also with objects.
JB, you can post an answer if you want to.

Thanks everyone for your coorporation
Ronit

0
 
LVL 5

Accepted Solution

by:
JimBob091197 earned 50 total points
ID: 1352175
Hi Ronit,

Here is the answer for AllocateHWnd and DeallocateHWnd.

Bye,
JB
0
 
LVL 3

Expert Comment

by:Matvey
ID: 1352176
-If you didn't notice, the component receives the "..._DeviceChange" message, so it's not only the eject method. The component actually receives all messages taht are posted to the top windows...

Cheers
0

Featured Post

Is Your Active Directory as Secure as You Think?

More than 75% of all records are compromised because of the loss or theft of a privileged credential. Experts have been exploring Active Directory infrastructure to identify key threats and establish best practices for keeping data safe. Attend this month’s webinar to learn more.

Question has a verified solution.

If you are experiencing a similar issue, please ask a related question

Suggested Solutions

In this tutorial I will show you how to use the Windows Speech API in Delphi. I will only cover basic functions such as text to speech and controlling the speed of the speech. SAPI Installation First you need to install the SAPI type library, th…
Hello everybody This Article will show you how to validate number with TEdit control, What's the TEdit control? TEdit is a standard Windows edit control on a form, it allows to user to write, read and copy/paste single line of text. Usua…
This Micro Tutorial will teach you how to censor certain areas of your screen. The example in this video will show a little boy's face being blurred. This will be demonstrated using Adobe Premiere Pro CS6.
This is used to tweak the memory usage for your computer, it is used for servers more so than workstations but just be careful editing registry settings as it may cause irreversible results. I hold no responsibility for anything you do to the regist…

920 members asked questions and received personalized solutions in the past 7 days.

Join the community of 500,000 technology professionals and ask your questions.

Join & Ask a Question

Need Help in Real-Time?

Connect with top rated Experts

16 Experts available now in Live!

Get 1:1 Help Now