How to not have a MainForm in Delphi?

Question

i've been trying to get some modeless forms in my application to appear on the taskbar - taking advantage of the new useful taskbar in Windows 7.

There's are many issues with the VCL that need to be undone before a form can exist on the taskbar.

But the final issue is that minimizing the form that the VCL has designated the main form causes all windows in the application to vanish.

Ten years ago, Peter Below (TeamB) documented these problems, and attempts to work around them. But there are some issues that cannot be solved. The issues run so deep within the VCL itself, that it's effectively impossible to make Delphi applications behave properly.

It all stems from the fact that the button you see on the toolbar does not represent the application's window; it represents the TApplications window, which is hidden and never seen. And then there is the application's MainForm, which is then imbued with special abilities where if it is minimized then it instructs the application to hide itself.

It seems to me that if i can do

Application.MainForm := nil;

then all these bugs would go away. The application can have its hidden window, and in the meantime i'll override every other form in the application, including my main form, with:

procedure TForm2.CreateParams(var params: TCreateParams ); 
begin 
   inherited CreateParams(params); 
   params.ExStyle := params.ExStyle or WS_EX_APPWINDOW; 
end; 

But in Delphi the Application.MainForm property is read-only.

How can i not have a MainForm in Delphi?

See also

• (stackoverflow) Delphi: What is Application.Handle?
• (newsgroup) Hiding Main Window but not child

Answer 1

You cannot run a GUI project without a MainForm assigned. The main message loop will exit immediately without one. However, that does not mean that the MainForm has to run your UI. You can use a blank hidden TForm as the assigned MainForm, and then have it instantiate your real MainForm as a secondary TForm. For example:

HiddenMainFormApp.dpr:

project HiddenMainFormApp;

uses
  ..., Forms, HiddenMainForm;

begin
  Application.Initialize;
  Application.CreateForm(THiddenMainForm, MainForm);
  Application.ShowMainForm := False;
  Application.Run;
end.

HiddenMainForm.cpp:

uses
  ..., RealMainForm;

procedure THiddenMainForm.FormCreate(Sender: TObject);
begin
  RealMainForm := TRealMainForm.Create(Self);
  RealMainForm.Show;
end;

RealMainForm.cpp:

procedure TRealMainForm.FormClose(Sender: TObject; var Action: TCloseAction);
begin
  Action := caFree;
  Application.Terminate;
end;

Alternatively:

HiddenMainFormApp.dpr:

project HiddenMainFormApp;

uses
  ..., Forms, HiddenMainForm, RealMainForm;

begin
  Application.Initialize;
  Application.CreateForm(THiddenMainForm, MainForm);
  Application.ShowMainForm := False;

  RealMainForm := TRealMainForm.Create(Application);
  RealMainForm.Show;
  RealMainForm.Update;

  Application.Run;
end.

RealMainForm.cpp:

procedure TRealMainForm.FormClose(Sender: TObject; var Action: TCloseAction);
begin
  Action := caFree;
  Application.Terminate;
end;