Multithreaded Programming (15)

The second parameter (starting time) for the next setwaitabletimer is specifically studied.

It has positive, negative, 0-valued three cases, preceded by a value of 0.

Learn about negative values (relative time), that is, how long it will take to start execution from the current count.

This relative time is 1/100 nanoseconds, for example, the assignment 3*10000000 is equivalent to 3 seconds.

1 s(秒) = 1,000　　　　　　 ms(毫秒);
1 s(秒) = 1,000,000　　　　 µs(微妙);
1 s(秒) = 1,000,000,000　　 ns(纳秒);
1 s(秒) = 1,000,000,000,000 ps(皮秒);

This example effect chart:

Code files:

Unit Unit1
Interface
uses
Windows, Messages, sysutils, variants, Classes, Graphics, Controls, Forms ,
Dialogs, Stdctrls; 　　
Type
TForm1 = Class (Tform)
Button1:tbutton;
Procedure Button1Click (Sender:tobject);
Procedure Formdestroy (sender:tobject);
End; 　
Var
Form1:tform1
Implementation
{$R *.DFM}
var
f:integer;
Hwaitabletimer:thandle;
Function Mythreadfun (p:pointer): DWORD; stdcall; 　
var
i,y:integer
Begin
Inc (f);
Y: = * f;
If WaitForSingleObject (Hwaitabletimer, INFINITE) = Wait_object_0 then
begin
For I: = 0 to 1000 do
B 　　　Egin
Form1.Canvas.Lock;
Form1.Canvas.TextOut (M, Y, IntToStr (i));
Form1.Canvas.Unlock;
Sleep (1);
End;
End;
Result: = 0;
End;
Procedure Tform1.button1click (sender:tobject); 　
var
Threadid:dword;
Duetime:int64;
Begin
Hwaitabletimer: = CreateWaitableTimer (Nil, True, nil);
Duetime: = -3*10000000; {3 seconds to execute}
SetWaitableTimer (Hwaitabletimer, duetime, 0, Nil, nil, False);
Repaint; F: = 0;
CreateThread (nil, 0, @MyThreadFun, nil, 0, ThreadID);
CreateThread (nil, 0, @MyThreadFun, nil, 0, ThreadID);
CreateThread (nil, 0, @MyThreadFun, nil, 0, ThreadID);
End;
Procedure Tform1.formdestroy (sender:tobject);
Begin
CloseHandle (hwaitabletimer);
End;
End.

Form file:

object Form1: TForm1
　Left = 0
　Top = 0
　Caption = 'Form1'
　ClientHeight = 116
　ClientWidth = 179
　Color = clBtnFace
　Font.Charset = DEFAULT_CHARSET
　Font.Color = clWindowText
　Font.Height = -11
　Font.Name = 'Tahoma'
　Font.Style = []
　OldCreateOrder = False
　OnDestroy = FormDestroy
　PixelsPerInch = 96
　TextHeight = 13
　object Button1: TButton
　　Left = 96
　　Top = 83
　　Width = 75
　　Height = 25
　　Caption = 'Button1'
　　TabOrder = 0
　　OnClick = Button1Click
　end
end