Get all running windows' titles

With this simple little code you can list the windows/software that are running. You can identify if some specific software is running or do some magic tricks with Windows API. It is up to you...

Quick Tutorial

Create a new Application Project. Project->New Project->Application->OK.
Add a TListbox and a TButton in the form.

Switch to source (F12). Add windows in the uses clause.

uses
..., windows, ...; 

Add the following function below implementation and {$R *.lfm} line:

function EnumWindowsProc(WHandle: HWND; LParM: LParam): LongBool;StdCall;Export;
var Title,ClassName:array[0..128] of char;
    sTitle,sClass,Linia:STRING ;

begin
 Result:=True;

 GetWindowText(wHandle, Title,128);
 GetClassName(wHandle, ClassName,128);

 sTitle:=Title;
 sClass:=ClassName;

 if IsWindowVisible(wHandle) then
 begin
  Linia:=sTitle+'        '+sClass+'       '+IntToHex(wHandle,4);
  Form1.ListBox1.Items.Add(Linia);
 end;

end;

This is the function which will help us to list all the windows. Add its declaration before the implementation line:

function EnumWindowsProc(WHandle: HWND; LParM: LParam): LongBool;StdCall;Export; 

Double click the button and write:

begin
  ListBox1.Clear; 
  EnumWindows(@EnumWindowsProc,0);
end;

Do additional changes to beautify your form.

Run It

Press F9 or Run->Run. The program will compile and run. Click the button. You will see a bunch of programs' titles that are currently running. Click the button again to get an updated list. (You may also implement a timer.)

Concept

The above code depends on windows unit, which is not cross-platform. It is strictly based on the Windows API. Our primary procedure is EnumWindows. If we have EnumWindows, why do we have another function? Because it does not return any values. It takes a function's name/pointer through which the output is sent to our program. The syntax is:

BOOL EnumWindows(

WNDENUMPROC lpEnumFunc, // pointer to callback function
LPARAM lParam // application-defined value
); 

A enumeration function should be given, which will, well, enumerate. In our case all windows' titles.

Download source zip

You can download the sample source code from here: http://db.tt/Sa19lv4u
Or here:  http://bit.ly/XzHRed
Size: 519KB

Ref:
http://delphi.about.com/od/windowsshellapi/l/aa080304a.htm
http://www.lazarus.freepascal.org/index.php?topic=13007.0