Solved

An Object with Handle

Posted on 1998-06-11
14
220 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
Threat Intelligence Starter Resources

Integrating threat intelligence can be challenging, and not all companies are ready. These resources can help you build awareness and prepare for defense.

 
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

How to run any project with ease

Manage projects of all sizes how you want. Great for personal to-do lists, project milestones, team priorities and launch plans.
- Combine task lists, docs, spreadsheets, and chat in one
- View and edit from mobile/offline
- Cut down on emails

Join & Write a Comment

Suggested Solutions

A lot of questions regard threads in Delphi.   One of the more specific questions is how to show progress of the thread.   Updating a progressbar from inside a thread is a mistake. A solution to this would be to send a synchronized message to the…
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…
Get a first impression of how PRTG looks and learn how it works.   This video is a short introduction to PRTG, as an initial overview or as a quick start for new PRTG users.
Here's a very brief overview of the methods PRTG Network Monitor (https://www.paessler.com/prtg) offers for monitoring bandwidth, to help you decide which methods you´d like to investigate in more detail.  The methods are covered in more detail in o…

746 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

9 Experts available now in Live!

Get 1:1 Help Now