How to hide an application from taskbar in Windows 7?

Question

I would like to hide an application from the Windows 7 taskbar.

I want to make something like a toolbar on the edge of the screen which does certain things when the user clicks on it, but I don't want it to show in the taskbar, since its a thing that i want to stay in the background.

I tried the instructions in the following post, but it did not work on my application:

How to hide a taskbar entry but keep the window form

Then i tried it on a new empty VCL Forms Application and it still did not work. I searched for other solutions, but they all do very much the same like in the linked post.

Has something changed, that makes that impossible in windows 7? Or is there anything you could think of, that could prevent it from working?

Answer 1

You can override the main form's CreateParam to remove the flag that forces the taskbar button (WS_EX_APPWINDOW) and additionally make the form owned by the application window. That's doing the opposite of the requirement for the shell to place a taskbar button for a window. From "Managing Taskbar Buttons":

[..] To ensure that the window button is placed on the taskbar, create an unowned window with the WS_EX_APPWINDOW extended style. [..]

Sample:

type
  TForm1 = class(TForm)
  protected
    procedure CreateParams(var Params: TCreateParams); override;
  end;

procedure TForm1.CreateParams(var Params: TCreateParams);
begin
  inherited;
  Params.ExStyle := Params.ExStyle and not WS_EX_APPWINDOW;
  Params.WndParent := Application.Handle;
end;

Don't change the state of MainFormOnTaskbar property of the 'Application' from its default 'True' if you use this method.

You can also remove the second line (..WndParent := ..) and instead set PopupMode of the form to pmExplicit in the object inspector to same effect.

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BTW, here's the documentation quote from the same topic for the solution TLama posted:

To prevent the window button from being placed on the taskbar, [...] As an alternative, you can create a hidden window and make this hidden window the owner of your visible window.

When you set MainFormOnTaskbar to false, the main form is owned by the application window by VCL design. And if you hide the application window, the requirement is fulfilled.