SimpleTimer, ver. 1.0.3

[Properties] [Methods] [Events]
[How To Use] [Known Bugs] [Comments]

SimpleTimer is a timer class. It has the same timer resolution as TTimer, but it is more lightweight because it's derived from TObject in stead of TComponent. Furthermore, the same handle is shared between multiple instances of SimpleTimer. This makes it ideal for developers who need a timer in their own components or applications, but want to keep the resource usage minimal.

Properties

Owner	property Owner: TComponent; The owner of the timer.	Read-only
Active	property Active: Boolean; Whether the timer is running.	Read-only

Methods

Create	type TSimpleTimerCallBackProc = procedure(AOwner: TComponent); stdcall; constructor (AOwner: TComponent; CallBackProc: TSimpleTimerCallBackProc); Creates a new TSimpleTimer instance. You need to declare a procedure of type TSimpleTimerCallBackProc which will be called continuously at the interval you specify in the Start method. NOTE: Be sure to declare the stdcall directive, as is normal practice with callback methods. NOTE: The callback method cannot be part of any class. It must be a simple method.	Returns new TSimpleTimer object
Start	function Start(MilliSecs: Cardinal): Boolean; Starts the timer, using the specified interval in millisecs. If the timer is already running it will be stopped, then restarted with the new interval. NOTE: If the method returns false it means the system has run out of timer resources. That's bad.	Returns true or false
Stop	function Stop: Boolean; Stops the timer.	Returns true or false

Events

No events. In stead your callback method is called when the timer fires.

How To Use

Creating and starting a SimpleTimer object
This example creates a SimpleTimer object associated with a TForm, using TimerProc1 as a callback method, then starts the timer so it fires every second:
```
procedure TForm1.FormCreate(Sender: TObject);
begin
  SimpleTimer1 := TSimpleTimer.Create(Self, @TimerProc1);
  SimpleTimer1.Start(1000);
end;
```

Example of callback method
This is what TimerProc1 might look like:

procedure TimerProc1(AOwner: TComponent); stdcall;
begin
  with (AOwner as TForm1) do
    ListBox1.Items.Add('SimpleTimer1 fired');
end;

Changing the interval
If you want to change the interval of a SimpleTimer object, simply call the Start method with the new interval.

Known Bugs

You may experience occasionally that you lose a timer event when you work with small intervals (approx. below 500 ms.). This is normal, and the same thing happens with a TTimer object. If you want precision you need a multimedia timer, not TTimer or TSimpleTimer which use the low-priority WM_TIMER message. WinXP has better handling of timers and will generally lose fewer timer events than other Windows versions.

Comments

SimpleTimer is freeware. Feel free to use and improve it, but please include all original files if you redistribute the zip-file. If you have any comments or corrections I would very much like to hear them.

Get the latest version from http://www3.brinkster.com/troels/delphi.asp.

Troels Jakobsen
delphiuser@get2net.dk