Classes.TThreadPriority Enumeration

TThreadPriority indicates the scheduling priority of a thread object on Windows.

Pascal

TThreadPriority = (
  tpIdle,
  tpLowest,
  tpLower,
  tpNormal,
  tpHigher,
  tpHighest,
  tpTimeCritical
);

C++

enum TThreadPriority {
  tpIdle,
  tpLowest,
  tpLower,
  tpNormal,
  tpHigher,
  tpHighest,
  tpTimeCritical
};

File

Classes

Description

The following are possible values of TThreadPriority:

Values	Meaning
tpIdle	The thread executes only when the system is idle. The system will not interrupt other threads to execute a thread with tpIdle priority.
tpLowest	The thread's priority is two points below normal.
tpLower	The thread's priority is one point below normal.
tpNormal	The thread has normal priority.
tpHigher	The thread's priority is one point above normal.
tpHighest	The thread's priority is two points above normal.
tpTimeCritical	The thread gets highest priority.

Delphi Examples:

Copy Code

{
This example shows how to create a thread and start it
running at a lower priority than the main execution thread.
Set the thread’s FreeOnTerminate property is True, so that
there is no need to free the thread when it finishes.  The
Execute procedure must be overridden in the extension class
of TThread or an "Abstract Error" will result. To create the
extension choose the File | New | Other | Thread Object menu.
}
procedure TForm1.Button1Click(Sender: TObject);
begin
  if (mythreadRunning = FALSE) then
  begin
    mythreadRunning:= TRUE;
    MyProcess := TMyThread.Create(True); { create suspended - secondprocess does not run yet }
    MyProcess.FreeOnTerminate := True; { don't need to cleanup after terminate }
    MyProcess.Priority := tpLower;  // set the priority to lower than normal
    MyProcess.Resume; { now run the thread }
  end
  else
    MessageDlg('This thread is still running.  You are going to hurt yourself!',
      mtInformation, [mbOk], 0);
end;

procedure TForm1.Button4Click(Sender: TObject);
begin
  if mythreadRunning then MyProcess.Terminate();
end;

procedure TMyThread.Execute;
var I: Integer;
begin
  Form1.Memo1.Lines.Add('Process has been running for this many seconds:');
  for I := 0 to 10 do
  begin
    if Terminated then break;
    Form1.Memo1.Lines.Add('Low priority process ' + InttoStr(I));
    Sleep(1000);
  end;
  mythreadRunning:= FALSE;
end;

procedure TYouThread.Execute;
var I: Integer;
begin
  Form1.Memo3.Lines.Add('Second low priority process has been running for this many seconds:');
  for I := 0 to 10 do
  begin
    if Terminated then break;
    Form1.Memo3.Lines.Add('Second low priority process ' + InttoStr(I));
    Sleep(1000);
  end;
    youthreadRunning:= FALSE;
end;

procedure TForm1.Button2Click(Sender: TObject);
var   I: Integer;
begin
  Form1.Memo2.Lines.Add('Do some work in the main process for 10 seconds:');
  for I := 0 to 10 do
  begin
    Form1.Memo2.Lines.Add('Main process ' + InttoStr(I));
    Sleep(1000);
  end;
end;

procedure TForm1.Button3Click(Sender: TObject);
begin
  if (youthreadRunning = FALSE) then
  begin
    youthreadRunning:= TRUE;
    YouProcess := TYouThread.Create(True); { create suspended – secondprocess does not run yet }
    YouProcess.FreeOnTerminate := True; { don't need to cleanup after terminate }
    YouProcess.Priority := tpLower;  // set the priority to lower than normal
    YouProcess.Resume; { now run the thread }
  end
  else
    MessageDlg('This thread is still running.  You are going to hurt yourself!',
      mtInformation, [mbOk], 0);
end;

procedure TForm1.Button5Click(Sender: TObject);
begin
  if youthreadRunning then YouProcess.Terminate();
end;

procedure TForm1.FormCreate(Sender: TObject);
begin
  mythreadRunning:= FALSE;
  youthreadRunning:= FALSE;
end;