Solved

How to perform regular screen refresh while processing?

Posted on 2008-10-26
16
2,064 Views
Last Modified: 2012-05-05
Hi

my application is processing data and it can take up to 10 minutes to do. It can make tens of millions of cycles... to have some sort of screen refresh and indicator I put this to every main procedure :

if counter mod 10000 then
begin
    StatusForm.Show;
    StatusForm.myLabel.Caption := 'Procesing #'+myIndicatorNo;
    Application.ProcessMessages;
end;


Now, this works OK. Obivously with 'IF' I make sure that refresh doesn't take too much of resources, because it CAN, at least in my application!

Now, I would like to have another, easier and much less code approach. So I was thinking of having a Timer that would do the same think every second.

Is this possible? Can Timer take a lot of resources, while waiting for 1 sec to pass? Is this, being executed on Timer event, actually possible in one-threaded application?

If this is possible for my application, please give me some pointers.

Thank you

0
Comment
Question by:Delphi_developer
  • 8
  • 4
  • 3
  • +1
16 Comments
 
LVL 31

Expert Comment

by:moorhouselondon
ID: 22808545
I would have thought that Timer is interrupt driven, and therefore uses less resources, but others here will have a clearer idea.
0
 
LVL 36

Expert Comment

by:Geert Gruwez
ID: 22808700
nope, not in 1 threaded app

the timer event will be put on the queue, and wait for the thread to process it
which off course will never happen as your calculation routine is using the 1 thread

you really need to put the calculation routine in a thread
if you want the GUI not to freeze
0
 
LVL 31

Expert Comment

by:moorhouselondon
ID: 22808733
I for one would be interested to know how to implement that
0
 
LVL 36

Accepted Solution

by:
Geert Gruwez earned 500 total points
ID: 22810346
well if is only 1 routine just put it in the
procedure Execute of a thread

I even wrote a Thread type for this, from which you can callback the progress

type

 

  TCallbackProc = procedure (aMessage: string; aMessageInfo: Integer = 0) of object;

 

  TCallbackThread = class(TThread)

  private

    FCallBack: TCallbackProc;

    FCallbackMsg: string;

    FCallbackMsgInfo: integer;

    procedure SynchedCallback;

  protected

    procedure DoCallback(aMsg: string; aMsgInfo: integer = 0); virtual;

    property Callback: TCallbackProc read FCallback;

  public

    constructor Create(aCallback: TCallbackProc; CreateSuspended: Boolean = False); reintroduce; virtual;

  end;

 

{ TCallbackThread }

 

constructor TCallbackThread.Create(aCallback: TCallbackProc; CreateSuspended: Boolean = False);

begin

  inherited Create(CreateSuspended);

  FreeOnTerminate := True;

  FCallback := aCallback;

end;

 

procedure TCallbackThread.DoCallback(aMsg: string; aMsgInfo: Integer = 0);

begin

  FCallbackMsg := aMsg;

  FCallbackMsgInfo := aMsgInfo;

  Synchronize(SynchedCallback);

end;

 

procedure TCallbackThread.SynchedCallback;

begin

  if Assigned(FCallback) then

    FCallBack(FCallbackMsg, FCallbackMsgInfo);

end;

Open in new window

0
 
LVL 36

Expert Comment

by:Geert Gruwez
ID: 22810347
Example of DB reading records

procedure TMyThread.Execute;

var I: Integer;

begin

  DoCallback('Thread started', 0);

 

  DoCallback('Records ' + IntToStr(Query.RecordCount)), 1);

  I := 0;

  while not Query.Eof do 

  begin

    Inc(I);

    DoCallback('Handling record ' + IntToStr(I), 2);

    Query.Next;

  end;

 

  DoCallback('Thread started', 0);

end;

Open in new window

0
 
LVL 36

Expert Comment

by:Geert Gruwez
ID: 22810366
in your Form create a thread with the callback proc assigned



type

  TForm1 = class(TForm)

    ProgressBar1: TProgressBar;

    Panel1:  TPanel;

  private

    fThread: TMyThread;

    procedure ProgressUpdate(aMessage: string; aMessageInfo: Integer = 0);

  end;
 

procedure TForm1.ProgressUpdate(aMessage: string; aMessageInfo: Integer = 0);

begin

  Panel1.Caption := aMessage;

  case aMessageInfo of

    0: ProgressBar1.Position := 0;

    1: 

    begin

      ProgressBar1.Position := 0;

      ProgressBar1.Max := StrToInt(Copy(aMessage, 8, Length(aMessage)));

    end;

    2: ProgressBar1.Position := ProgressBar1.Position + 1;

    3: 

    begin

      ProgressBar1.Position := ProgressBar1.Max;

      fThread := nil;

    end;

  end;

end;
 

procedure TForm1.Button1Click(Sender: Object);

begin

  if not Assigned(fThread) then 

    fThread := TMyThread.Create(ProgressUpdate);

end;

Open in new window

0
 
LVL 36

Expert Comment

by:Geert Gruwez
ID: 22810388
o yes,
no need to call
Application.ProcessMessages
0
 
LVL 31

Expert Comment

by:moorhouselondon
ID: 22810626
GG:

v. comprehensive ty.  I hope it answers DD's q!
0
Free Trending Threat Insights Every Day

Enhance your security with threat intelligence from the web. Get trending threat insights on hackers, exploits, and suspicious IP addresses delivered to your inbox with our free Cyber Daily.

 

Author Comment

by:Delphi_developer
ID: 22829566
@Geert Gruwez: Thank you! I will need some time to test if this can be applied to my app...
0
 

Author Closing Comment

by:Delphi_developer
ID: 31514375
I decided that running my app in threads is a little too complicated... too many errors and too much things still to learn about threads, for now.

But thank you for the solution, I will definately use it in another app.

I will go back to  Application.ProcessMessages; for now, it is the easiset way and it works 100% for my app.

Thank you
0
 
LVL 36

Expert Comment

by:Geert Gruwez
ID: 22907584
Please read the Help about giving grades for answers.
If someone gives you an excellent approach then the answer deserves an A
The questioner deserves a B for not implementing it.
And not vice versa
0
 

Author Comment

by:Delphi_developer
ID: 22907626
Sorry, I thought C is for not using the proposed solution and A for it to be a solution to the question. So, I gave B because it is a good solutions, but not gonna use it as a solutinos for my question... I see I messed up.

0
 
LVL 36

Expert Comment

by:Geert Gruwez
ID: 22909583
nobody's perfect :)
0
 
LVL 36

Expert Comment

by:Geert Gruwez
ID: 22973718
>>But thank you for the solution, I will definately use it in another app.

don't you think you should change the grade to an A since you are going to use the solution ?
0
 
LVL 1

Expert Comment

by:Vee_Mod
ID: 22974940
Grade change by Asker request.

Vee_Mod
Experts Exchange Moderator
0
 

Author Comment

by:Delphi_developer
ID: 22974960
@Geert_Gruwez: thank you for pointing this out - I didn't know I can do this, until your comment and a quick browse through the Help

@Vee_Mod: Thank you.
0

Featured Post

Highfive + Dolby Voice = No More Audio Complaints!

Poor audio quality is one of the top reasons people don’t use video conferencing. Get the crispest, clearest audio powered by Dolby Voice in every meeting. Highfive and Dolby Voice deliver the best video conferencing and audio experience for every meeting and every room.

Join & Write a Comment

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…
Access reports are powerful and flexible. Learn how to create a query and then a grouped report using the wizard. Modify the report design after the wizard is done to make it look better. There will be another video to explain how to put the final p…
This video gives you a great overview about bandwidth monitoring with SNMP and WMI with our network monitoring solution PRTG Network Monitor (https://www.paessler.com/prtg). If you're looking for how to monitor bandwidth using netflow or packet s…

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

13 Experts available now in Live!

Get 1:1 Help Now