Step by step

Folks,

A light for everybody. First of all, I’ll use two other usefull functions I posted on this site:

GetHwndClass

GetHwndText

And now the magic:

 Delphi | 
 copy code |
?
 
01
uses Windows, TLHelp32;
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type
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  TWalkOnHandlesCallback = function(AHwnd, AParentHWnd: HWND;
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    AClass, AText: string; AFlag: Integer): boolean of object;
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function WalkOnHandles(AParent: HWND; AFlag: integer;
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  ACallback: TWalkOnHandlesCallback): Integer;
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var
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  CurrHWnd: HWND;
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begin
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  Result := 0;
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  CurrHWnd := GetTopWindow(AParent);
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  while CurrHWnd <> 0 do
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  begin
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    Result := Result + 1;
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    if Assigned(ACallback) then
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      if not ACallback(CurrHWnd, AParent,
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        GetHwndClass(CurrHWnd), GetHwndText(CurrHWnd), AFlag) then
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        Break;
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    CurrHWnd := GetNextWindow(CurrHWnd, GW_HWNDNEXT);
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  end;
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end;
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function WalkOnHandlesOfExe(AExeName: string; AFlag: integer;
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  ACallback: TWalkOnHandlesCallback): Integer;
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var
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  PID, CheckPID: DWord;
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  hSnapShot: THandle;
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  ProcessEntry: TProcessEntry32;
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  CurrHWnd: HWND;
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begin
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  Result := 0;
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  PID := 0;
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  hSnapShot := CreateToolhelp32Snapshot((TH32CS_SNAPALL), 0);
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  ProcessEntry.dwSize := SizeOf(TProcessEntry32);
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  Process32First(hSnapShot, ProcessEntry);
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  repeat
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    if ProcessEntry.szExeFile = AExeName then
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    begin
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      PID := ProcessEntry.th32ProcessID;
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      Break;
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    end;
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  until Process32Next(hSnapShot, ProcessEntry) = false;
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  CloseHandle(hSnapShot);
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  if PID > 0 then
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  begin
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    CurrHWnd := GetTopWindow(GetDesktopWindow);
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    while CurrHWnd <> 0 do
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    begin
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      Result := Result + 1;
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      GetWindowThreadProcessID(CurrHWnd, @CheckPID);
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      if CheckPID = PID then
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        if Assigned(ACallback) then
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          if not ACallback(CurrHWnd, 0,
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            GetHwndClass(CurrHWnd), GetHwndText(CurrHWnd), AFlag) then
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            Break;
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      CurrHWnd := GetNextWindow(CurrHWnd, GW_HWNDNEXT);
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    end;
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  end;
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end;

Now let me explain what this big code do.

This code its only a light, a simple idea, about how you can navigate through the Windows Objects (Handle) from everywhere.

A simple example:

Create a TMemo named mmoLog

Link OnCreate of the Main Form

Create a the callback on the Main Form class

 Delphi | 
 copy code |
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01
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  TForm1 = class(TForm)
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    mmoLog: TMemo;
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    procedure FormCreate(Sender: TObject);
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  private
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    { Private declarations }
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  public
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    function WalkCall(AHwnd, AParentHWnd: HWND;
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      AClass, AText: string; AFlag: Integer): boolean;
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  end;
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The rest of the code:

 Delphi | 
 copy code |
?
 
01
02
procedure TForm1.FormCreate(Sender: TObject);
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begin
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  WalkOnHandlesOfExe('delphi32.exe', 0, WalkCall);
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end;
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function TForm1.WalkCall(AHwnd, AParentHWnd: HWND; AClass,
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  AText: string; AFlag: Integer): boolean;
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begin
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  Result := True;
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  mmoLog.Lines.Add(stringofChar(' ', AFlag)  + Format('%d: [ %s ] %s', [AHwnd, AClass, AText]));
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  WalkOnHandles(AHwnd, AFlag + 2, WalkCall);
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end;
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This example will list all Windows Objects on the Delphi application and will result a idented log on the mmoLog.

Simple uhm?

WalkOnHandles
Walk on all handles by the Z-order of the specified Parent.

WalkOnHandlesOfExe
Walk on all handles by the Z-order that have DesktopWindow as parent and the Application as owner.

Tags: CreateToolhelp32Snapshot, Delphi, GetNextWindow, GetTopWindow, GetWindowThreadProcessID, Usefull Function, WalkOnHandlesOfExe

This entry was posted on Thursday, July 3rd, 2008 at 8:36 pm and is filed under articles. You can follow any responses to this entry through the RSS 2.0 feed. You can leave a response, or trackback from your own site.