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hakanfa
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WM_GETTEXT problem

Hi Everyone,
I have program that should read both textboxes and textlabels from another program. I'm retrieving the handle for the controls with EnumWindows and EnumChildWindows. First I tried the GetWindowsText which worked fine, but not with the Edit Boxes. So I'm now trying to use the WM_GETTEXT directly but with no better success.. I'm not getting any text at all..

Here is the code used:
function EnumTextChildProc(AHandle: hWnd; AnObject: TObject): BOOL; stdcall;
var
  caption: array[0..3000] of Char;
  s: string;
begin
  Result := True;
  SendMessage(AHandle, WM_GETTEXT, Sizeof(caption), integer(@caption));
  s := Caption;
  ShowMessage(s);
end;


Any solutions or workarounds for this problem?

(using Win 8 and Delphi XE3)
Delphi

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Last Comment
hakanfa

8/22/2022 - Mon
Sinisa Vuk

http://www.delphifaq.com/faq/delphi/windows_GUI/f451_0.htm

Your example works ok for me when used as:
procedure TForm1.BitBtn1Click(Sender: TObject);
begin
  EnumChildWindows(Self.Handle, @EnumTextChildProc, 0);
end;

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(i put edit and button component on form)

http://borland.public.delphi.winapi.narkive.com/Qw0wAIR1/wm-gettext-doesn-t-work-in-the-icq-chat-window
Thommy

Download Winhandles.zip

Try out this wonderful example of getting text from any control of all running processes and applications...
Thommy

Check my below demo code to see how to get edit text from another program using Windows message WM_GETTEXT... (Finding child windows in other applications by ClassName)

unit Unit1;

interface

uses
  Windows, Messages, SysUtils, Variants, Classes, Graphics, Controls, Forms,
  Dialogs, StdCtrls;

type
  TForm1 = class(TForm)
    Button1: TButton;
    procedure Button1Click(Sender: TObject);
  private
    { Private-Deklarationen }
    function nGetChildHandle: Integer;
  public
    { Public-Deklarationen }
  end;

function EIFindChildWindow(hwndParent: HWnd; ClassName: PChar): HWnd;
function EIGetWindowClass(const nHandle: HWnd): string;

var
  Form1: TForm1;

implementation

var
  hwndFindChildWindow : HWND;


{$R *.dfm}

function EnumTextChildProc(AHandle: hWnd): BOOL; stdcall;
var
  AText: array[0..255] of Char;
  s: string;
begin
  Result := True;
  PostMessage(AHandle, WM_GETTEXT, Sizeof(AText), integer(@AText));
  s := strpas(AText);
  ShowMessage(s);
end;

function GetTextFromHandle(wndhandle: HWnd): string;
var
 textlength: integer;
 text: PChar;
begin
   result := '';
   if wndhandle = 0 then Exit;
   textlength := SendMessage(wndhandle, WM_GETTEXTLENGTH, 0, 0);
   if textlength <> 0 then
     begin
       GetMem(Text, textlength+1);
       SendMessage(wndhandle, WM_GETTEXT, textlength+1, Integer(text));
       Result := text;
       FreeMem(text);
     end;

end;

function EIGetWindowClass(const nHandle: HWnd): string;
var
  szClassName: array[0..255] of char;
begin
  GetClassName(nHandle, szClassName, 255);
  Result := szClassName;
end;

function EnumWindowsForFindChildWindowProc(WHandle: HWND; lParam: LPARAM): BOOL; export; stdcall;
const
  MAX_WINDOW_NAME_LEN = 80;
var
  sTargetClassName: string;
  nHandle: HWnd;
  sCurrClassName: string;
  bResult: Boolean;
begin
  if (hwndFindChildWindow<>0) then
    exit;
  sTargetClassName := PChar(lParam);
  sCurrClassName := EIGetWindowClass(WHandle);
  bResult := CompareText(sCurrClassName, sTargetClassName) = 0;
  If (bResult) then
    hwndFindChildWindow := WHandle
  else
    EIFindChildWindow(WHandle, PChar(lParam));
end;

function EIFindChildWindow(hwndParent: HWnd; ClassName: PChar) : HWnd;
begin
  try
    EnumChildWindows(hwndParent, @EnumWindowsForFindChildWindowProc, LongInt(PChar(ClassName)));
    Result := hwndFindChildWindow;
  except
    on Exception do
      Result := 0;
  end;
end;

function TForm1.nGetChildHandle: Integer;
var
  nParentHandle: HWnd;
  nChildHandle: HWnd;
begin
  //Find parent window
  nParentHandle := FindWindow(nil, PChar('Your window title'));
  if nParentHandle = 0 then
    raise Exception.Create('Couldn''t find the main window !');

  //Find child window (TEdit)
  nChildHandle := EIFindChildWindow(nParentHandle, PChar('TEdit'));
  if nChildHandle = 0 then
    raise Exception.Create('Couldn''t find the child window !');

  Result := nChildHandle;
end;

procedure TForm1.Button1Click(Sender: TObject);
var
  TheChildHandle: hwnd;
begin
  TheChildHandle:=nGetChildHandle;
end;

end.

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hakanfa

ASKER
Hi Tommy, thanks for the pice of code. Works fine with small modifications for own needs. Though one question, you use both send-message and post-message command, any specific reason for that? Anyhow, works fine, thanks!

-Hokki
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Thommy

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hakanfa

ASKER
Excellent, thank you very much!