How to not have a MainForm in Delphi? - 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;

Answer 2

You can't, especially in Delphi 5.
Your quote concerning the TApplication window being the one seen on the task bar hasn't been true for several Delphi versions now (I believe D2007 changed it).
Because you're using Delphi 5, you're using an outdated copy of Delphi; current versions have almost none of the things you're writing about any longer. I'd suggest you upgrade to a later version of Delphi (D5 is extremely old); Delphi 2007 if you need to avoid Unicode, Delphi XE if you can use (or don't mind having) Unicode support in the VCL and RTL.
The things you're describing are not bugs, BTW. They were intentional design decisions made at the time Delphi 1 was being designed, and through Delphi 7 worked fine with the versions of Windows that were available. Changes in later versions of Windows (XP/Vista/Win7 and the equivalent Server versions) made changes in that architecture necessary, and they were made as Delphi progressed along with Windows. Because you've chosen not to progress with your version of Delphi to keep it more recent doesn't make the things you write about magically become bugs. :-)

Answer 3

Having Application.MainForm assigned seems not to be a problem here for showing another modeless form on the taskbar while minimizing the MainForm.
Project1.dpr:
program Project1;
uses
Forms,
Windows,
Unit1 in 'Unit1.pas' {MainForm},
Unit2 in 'Unit2.pas' {Form2};
{$R *.res}
var
MainForm: TMainForm;
begin
Application.Initialize;
Application.CreateForm(TMainForm, MainForm);
ShowWindow(Application.Handle, SW_HIDE);
Application.Run;
end.
Unit1.pas:
unit Unit1;
interface
uses
Windows, Messages, Classes, Controls, Forms, StdCtrls, Unit2;
type
TMainForm = class(TForm)
ShowForm2Button: TButton;
ShowForm2ModalButton: TButton;
procedure ShowForm2ButtonClick(Sender: TObject);
procedure FormCreate(Sender: TObject);
procedure ShowForm2ModalButtonClick(Sender: TObject);
private
FForm2: TForm2;
procedure ApplicationActivate(Sender: TObject);
procedure Form2Close(Sender: TObject; var Action: TCloseAction);
procedure WMSysCommand(var Msg: TWMSysCommand); message WM_SYSCOMMAND;
protected
procedure CreateParams(var Params: TCreateParams); override;
end;
implementation
{$R *.dfm}
procedure TMainForm.FormCreate(Sender: TObject);
begin
Visible := True; //Required only for MainForm, can be set designtime
Application.OnActivate := ApplicationActivate;
end;
procedure TMainForm.ApplicationActivate(Sender: TObject);
{ Necessary in case of any modal windows dialog or modal Form active }
var
TopWindow: HWND;
I: Integer;
begin
TopWindow := 0;
for I := 0 to Screen.FormCount - 1 do
begin
Screen.Forms[I].BringToFront;
if fsModal in Screen.Forms[I].FormState then
TopWindow := Screen.Forms[I].Handle;
end;
Application.RestoreTopMosts;
if TopWindow = 0 then
Application.BringToFront
else
SetForegroundWindow(TopWindow);
end;
procedure TMainForm.CreateParams(var Params: TCreateParams);
begin
inherited CreateParams(Params);
with Params do
begin
ExStyle := ExStyle or WS_EX_APPWINDOW;
WndParent := GetDesktopWindow;
end;
end;
procedure TMainForm.WMSysCommand(var Msg: TWMSysCommand);
begin
if Msg.CmdType = SC_MINIMIZE then
ShowWindow(Handle, SW_MINIMIZE)
else
inherited;
end;
{ Testing code from here }
procedure TMainForm.ShowForm2ButtonClick(Sender: TObject);
begin
if FForm2 = nil then
begin
FForm2 := TForm2.Create(Application); //Or: AOwner = nil, or Self
FForm2.OnClose := Form2Close;
end;
ShowWindow(FForm2.Handle, SW_RESTORE);
FForm2.BringToFront;
end;
procedure TMainForm.Form2Close(Sender: TObject; var Action: TCloseAction);
begin
Action := caFree;
FForm2 := nil;
end;
procedure TMainForm.ShowForm2ModalButtonClick(Sender: TObject);
begin
with TForm2.Create(nil) do
try
ShowModal;
finally
Free;
end;
end;
end.
Unit2.pas:
unit Unit2;
interface
uses
Windows, Messages, Classes, Controls, Forms;
type
TForm2 = class(TForm)
private
procedure WMSysCommand(var Msg: TWMSysCommand); message WM_SYSCOMMAND;
protected
procedure CreateParams(var Params: TCreateParams); override;
end;
implementation
{$R *.dfm}
procedure TForm2.CreateParams(var Params: TCreateParams);
begin
inherited CreateParams(Params);
with Params do
begin
ExStyle := ExStyle or WS_EX_APPWINDOW;
WndParent := GetDesktopWindow;
end;
end;
procedure TForm2.WMSysCommand(var Msg: TWMSysCommand);
begin
if Msg.CmdType = SC_MINIMIZE then
ShowWindow(Handle, SW_MINIMIZE)
else
inherited;
end;
end.
(Tested with D5 and D7 on XP and Win7.)
(And yes, you may flag this as being not an answer, because it isn't: There still is a MainForm. But I dó like to think this answers the question behind the question...)

Answer 4

I can't speak for Delphi 5, but in Delphi 7 you can definitely run without a mainform if you're willing to get your hands dirty. I covered a lot of the details in another answer here.
Since Delphi 5 doesn't have the MainFormOnTaskbar property, you need to do the following in your dpr:
// Hide application's taskbar entry
WasVisible := IsWindowVisible(Application.Handle);
if WasVisible then
ShowWindow(Application.Handle, SW_HIDE);
SetWindowLong(Application.Handle, GWL_EXSTYLE,
GetWindowLong(Application.Handle, GWL_EXSTYLE) or WS_EX_TOOLWINDOW);
if WasVisible then
ShowWindow(Application.Handle, SW_SHOW);
// Hide the hidden app window window from the Task Manager's
// "Applications" tab. Don't change Application.Title since
// it might get read elsewhere.
SetWindowText(Application.Handle, '');
That will hide the application window, and as long as you override your form's CreateParams to set Params.WndParent := 0 each of them will have a taskbar entry of their own. Application.MainForm isn't assigned, so things like the minimize override aren't an issue, but you do have to be careful about any code that assumes MainForm is valid.

Answer 5

You can put your modeless forms in a dll, then they act pretty much on their own. (If you do not use the Application instance of the dll while creating them (Application.CreateForm) then Application.Mainform is nil in the dll).
Of course this might not be feasible depending on what the forms might need to do.

Answer 6

Actually most of what you are complaining about is in fact the design of Windows rather than the VCL. See Windows Features for all the details.
The crux of the matter is the owner property, and I mean the windows owner rather than the VCL owner.
An owned window is hidden when
its owner is minimized.
If you wish to be able to minimise the main form without other windows being hidden then you need to get on top of how owned windows work.