Reading data from a Delphi grid

Question

I have an application in Delphi with a grid.

I need to create another application, which should

a) read data from the grid and b) write data into the grid,

i. e. emulate the actions of a human user.

In order to read data from the table, I use following code:

Procedure TForm1.Button1Click(Sender: TObject);
type
  PForm = ^TForm;
  PClass = ^TClass;
var
  formPtr : PForm;
  I: Integer;
  msg : string;
  windowHandle : HWND;
begin
  windowHandle := FindWindow('TForm1', 'FORMSSSSS');
  formPtr := PForm(GetVCLObjectAddr(windowHandle) + 4);
  if (not Assigned(formPtr)) then Exit;
  for I := 0 to formPtr^.ControlCount - 1 do // Error
  begin
    msg := msg + formPtr^.Controls[i].Name;
    if formPtr^.Controls[i].Name = 'StringGrid1' then
    begin
      msg := TStringGrid(formPtr^.Controls[i]).Cells[1, 1];
    end;

  end;
  ShowMessage(msg);
end;


function GetVCLObjectAddr(AHandle: HWND): DWORD;
var
  pid: DWORD;
begin
  pid := 0;
  GetWindowThreadProcessId(AHandle, pid);
  if (pid =0) then
  begin
    Result := 0;
    Exit;
  end;
  Result := GetPropW(AHandle, PWideChar(WideString(Format('Delphi%.8X', [PID]))))
end;

In the line with the "Error" comment, following problem occurs:

Project Project1.exe raised exception class EAccessViolation with message 'Access violation at address 0046C8C3 in module 'Project1.exe'. Read of address 01262984'.

When I put a breakpoint on that line and inspect the value of the expression "formPtr^" in the "Watches" tab, I get "Inaccessible value" message.

How should the code be modified in order to be able to read data from the grid?

UPD:

If I change the code to the version given below, the memory problem disappears. But another problem arises - control count is equal to zero.

Procedure TForm1.Button1Click(Sender: TObject);
var
  formPtr : TForm;
  I: Integer;
  msg : string;
  windowHandle : HWND;
begin
  windowHandle := FindWindow('TForm1', 'FORMSSSSS');
  formPtr := TForm(GetVCLObjectAddr(windowHandle) + 4);
  if (not Assigned(formPtr)) then Exit;
  for I := 0 to formPtr.ControlCount - 1 do
  begin
    msg := msg + formPtr.Controls[i].Name;
    if formPtr.Controls[i].Name = 'StringGrid1' then
    begin
      msg := TStringGrid(formPtr.Controls[i]).Cells[1, 1];
    end;    
  end;
  ShowMessage(msg);
end;

That's not going to work. Your two processes have isolated address spaces. An address is only meaningful in the context of the process that owns that memory. You are going to need to expose an automation interface so that one process can automate actions in the other process. — David Heffernan
Are there any examples of how to do it? Basically, I need to develop application A (in Delphi or C# or C++), which will control (press buttons, read/write to/from text fields) Delphi application B (which I cannot modify). — Dmitrii Pisarenko
You can find some good advice how to communicate between two proccesses here:moving data between processes. — LU RD
Regarding your update, it's still not going to work. You are burying your head in the sand. You've got two isolated address spaces. It's time for you to accept that. — David Heffernan

David Heffernan David Heffernan · Accepted Answer · 2012-09-17T10:19:34

That approach cannot work. Your two processes have isolated address spaces. An address, and therefore an object, is only meaningful in the context of the process that owns that address or object. You can only call methods on objects that reside in your process.

Reading data from a Delphi grid

1 Answers