[SOLVED] EnumWindows doesnt Finish
lazarus / 34-Windows

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Cliff48 · 2015-07-02 00:07

The Following code used to work, but now EnumWindows never finishes 
/   returns.

Code: [Select]function AllWindows(hW: THandle; List: Integer):
Boolean; stdcall;
var
  l:      LongInt;
  found:  Boolean = false;
  wCaption:     String[255];
begin
  Result := True;
  l := SendMessage(hW, WM_GETTEXT, 254, LongInt(@wCaption[1]));
    if l > 0 then begin
      wCaption[0] := char(l);
      FormEnum.cb1.Items.add(wCaption);
    end;
  showMessage(IntToHex(hW, 8) + ' ' + IntToStr(l));
end;
   
 procedure TFormEnum.FormCreate(Sender: TObject);
begin
  ShowMessage('Enum Windows');
  enumWindows(@AllWindows, 0);
  showmessage('Pause');
end;      

EnumW calls the AllWindows Function many times, but after it is done,
the system is left in a loop and ShowMessage('Pause') is never
executed.

This is a Function I have in a working program and the above was
created to isolate/demonstrate the problem I'm having.
One thing different, is that the working program is compiled with
{$mode Objfpc}{$H+}   but to compile the above I had to change to: 
{$mode Delphi}{$H+}  which I dont understand why.

I assume I have done something silly, but I cant see it.  Any help
would be appreciated.

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Cliff48 · 2015-07-02 00:32

I added

    if IsWindowVisible(hW) then 

before the SendMessage(hW, WM_GETTEXT .........

Obviously Windows hangs waiting for a response from a non-visible
window.

Still curious as to why I needed to compile in Delphi mode tho.

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typo · 2015-07-02 00:37

You need to replace mode ObjFPC by mode Delphi:
Code: [Select]//{$mode objfpc}
{$mode delphi}{$H+}

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Cliff48 · 2015-07-02 01:29

Quote from: typo on July 02, 2015, 02:37:33 amYou need to replace mode
ObjFPC by mode Delphi:
Code: [Select]//{$mode objfpc}
{$mode delphi}{$H+}

Can someone explain why i had to change ... and why it compiled with
objfpc previously?

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atroesch · 2025-11-27 19:12

i know a really old thread but i got the same question..

why it only compiles in delphi Mode?

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PascalDragon · 2025-11-27 20:10

Quote from: atroesch on November 27, 2025, 08:12:10 pmi know a really
old thread but i got the same question..

why it only compiles in delphi Mode?

I assume the error message is the following:

Code: [Select]tenumwin.pp(25,26) Error: Incompatible type for arg no.
1: Got "<address of function(QWord;LongInt):Boolean;StdCall>",
expected "<procedure variable type of
function(QWord;Int64):LongBool;StdCall>"
The reason for this is that in mode Delphi the AllWindows creates an
untyped pointer which can then be converted to a ENUMWINDOWSPROC. If
you remove the @ which is the more correct one in mode Delphi then it
will fail with the same error.

The correct solution is to declare the function AllWindows correctly,
namely:

Code: Pascal  [Select][+][-]window.onload = function(){var x1 =
document.getElementById("main_content_section"); if (x1) { var x =
document.getElementsByClassName("geshi");for (var i = 0; i function
AllWindows(hW: HWND; List: LPARAM): WINBOOL; stdcall;
This way it will compile in both modes (with the @, though in mode
Delphi it shouldn't be used).

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atroesch · 2025-11-27 20:34

thank you very much.
got it fixed