[DUG] Best way to make this thread safe

[Matt Comb]

Because you are utilizing a control on your main form (i.e. your main
thread), you must call synchronize in order to force your main thread to
stop what its doing and run your log call. This will insure that the UI is
not using that control when you decide to play around with it.

Excuse Pigeon code...

e.g.

TSomeThread = class(TThread)
FErrorText: string;
Property ErrorText: string read FErrorText write FErrorText; Procedure
InternalLogStuff Procedure LogStuff(LogMessage)'


And then in code you would do the following

Blah blah

Procedure LogStuff(LogMessage: string);
Begin
  ErrorText := LogMessage;
  Synchronize(InternalLogStuff);
End;

Procedure InternalLogStuff;
Begin
  Do Whatever you have to do to log it.
End;

Regards,

Matt.
-----Original Message-----
From: delphi-bounces at delphi.org.nz [mailto:delphi-bounces at delphi.org.nz] On
Behalf Of Nick
Sent: Thursday, 17 May 2007 9:08 a.m.
To: NZ Borland Developers Group - Delphi List
Subject: [DUG] Best way to make this thread safe

I got a function here I use for logging to a richedit on my main form 
(this is just in functions unit)

Procedure WriteLog(sString : string; opt : LogOption);
Begin
  With frmMain.reLog do
    begin
      If lines.Count > 200 then lines.Delete(0);

      lines.add(sString);
      SelStart := length(text) - (length(sString)+2);
      SelLength := length(sString);
      Case LogOption(opt) of
        loStart   : begin SelAttributes.Style := [fsbold]; 
SelAttributes.Color := clBlue;   end;
        loNormal  : begin SelAttributes.Style := [];       
SelAttributes.Color := clBlack;  end;
        loError   : begin SelAttributes.Style := [fsbold]; 
SelAttributes.Color := clRed;    end;
        loFinished: begin SelAttributes.Style := [fsbold]; 
SelAttributes.Color := clBlue; lines.add('');  end;
      End;
      SelStart := Length(Text);
      Perform(EM_SCROLLCARET, 0, 0);
    end;
End;

Now I want to use that function in my threads to log things. However if 
I call it just like this
  WriteLog('Failed to connect! DB Error', loError);
I could run into access violations
But not quite sure the best way to do this to make it thread safe and 
use as little extra code as possible..

Should I create my own function like this
  WriteLogThread('Failed to connect! DB Error', loError);
in my TThread
and then in that procedure just do
criticalsection start
  WriteLog(message, st);  //this calls the function in my general 
functions unit
criticalsection end
or could I just use critical sections in my functions unit around the 
procedure.

I hope that makes sense =)
Thanks guys.
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