Create mainform after login form closes

[talorigomat]

I'm trying to display a login form and then only create and display the application main form if password is correct. however I am getting a "failed to create win32 control error: 1407 : cannot find class in file win32 controls.pp in line 217"

The login form  has the following  code which I found on a Delphi site

Code: Pascal  [Select][+][-]

1. unit login;
2.  
3. {$mode objfpc}{$H+}
4.  
5. interface
6.  
7. uses
8.   Classes, SysUtils, FileUtil, Forms, Controls, Graphics, Dialogs, StdCtrls;
9.  
10. type
11.  
12.   { TLoginForm }
13.  
14.   TLoginForm = class(TForm)
15.     LogInButton: TButton;
16.     passwordEdit: TEdit;
17.     pwdLabel: TLabel;
18.     procedure LogInButtonClick(Sender: TObject);
19.   private
20.  
21.   public
22.     class function Execute : boolean;
23.   end;
24.  
25. var
26.   LoginForm: TLoginForm;
27.  
28. implementation
29.  
30. {$R *.lfm}
31.  
32. { TLoginForm }
33.  
34. class function TLoginForm.Execute: boolean;
35. begin
36.   with TLoginForm.Create(nil) do
37.   try
38.     Result := ShowModal = mrOk;
39.   finally
40.     Free;
41.   end;
42. end;
43.  
44. procedure TLoginForm.LogInButtonClick(Sender: TObject);
45. begin
46.   if passwordEdit.Text = 'LetMeIn' then
47.     ModalResult := mrOK
48.   else
49.     ModalResult := mrAbort;
50. end;
51.  
52. end.
53.  

And the project source file ha the following

Code: Pascal  [Select][+][-]

1.  
2. program project1;
3.  
4. {$mode objfpc}{$H+}
5.  
6. uses
7.   {$IFDEF UNIX}{$IFDEF UseCThreads}
8.   cthreads,
9.   {$ENDIF}{$ENDIF}
10.   Interfaces, // this includes the LCL widgetset
11.   Forms, main, login
12.   { you can add units after this };
13.  
14. {$R *.res}
15.  
16. begin
17.   if TLoginForm.Execute then
18.     begin
19.       RequireDerivedFormResource:=True;
20.       Application.Initialize;
21.       Application.CreateForm(TTMainForm, TMainForm);
22.       Application.Run;
23.     end
24.   else
25.     Application.MessageBox('Not allowed in','Password Protected');
26. end.
27.  

[ASerge]

TApplication.Initialize initializes the widgetset (and more).

Code: Pascal  [Select][+][-]

1. ...
2. begin
3.   RequireDerivedFormResource:=True;
4.   Application.Initialize; // Need first!
5.   if TLoginForm.Execute then
6.   begin
7.     Application.CreateForm(TTMainForm, TMainForm);
8.     Application.Run;
9.   end
10.   else
11.     Application.MessageBox('Not allowed in','Password Protected');
12. end.
13.  

[howardpc]

Two minor points:

You don't need the global LoginForm variable which Lazarus added to your login unit - it should be deleted.
Unfortunately the Application.MessageBox routine does not take account of the length of the window title when sizing the dialog, so you will probably need to do something like

Code: Pascal  [Select][+][-]

1. Application.MessageBox('Not allowed in       ','Password protected');

in order to read the full window title, else it will be truncated.

[talorigomat]

Thank you both.  I made the changes as suggested.  When I run the program I get the error:
"Raised exception class 'EResNotFound' with message: For resource TLoginForm not found.  For rosourceless forms Create new constructor must be used.  See the global variable RequiredFormResource"

If I change LoginForm.Execute methos to use the Create new method.

Code: Pascal  [Select][+][-]

1. class function TLoginForm.Execute: boolean;
2. begin
3.   with TLoginForm.CreateNew(nil) do // < changed from TLoginForm.Create(nil)
4.   try
5.     Result := ShowModal = mrOk;
6.   finally
7.     Free;
8.   end;
9. end;
10.  

The program runs but the form that is first displayed has no cotrols on it and when closed the application stops

I'm using lazarus 1.8.0 RC4 on Window 10.  I'll check my signature to reflect this

[FTurtle]

If your form made in designer then add to code {$R *.lfm} and use Create :

Code: Pascal  [Select][+][-]

1. implementation
2.  
3. {$R *.lfm}
4.  

[howardpc]

The Delphi code you found assumed you had created unit login as a form which had its appropriate .dfm resource file (.lfm in Lazarus).

If you want to have a resourceless login form you have to instantiate the form's controls in code. Something along these lines:

Code: Pascal  [Select][+][-]

1.   unit uResourcelessLoginForm;
2.  
3.   {$mode objfpc}{$H+}
4.  
5.   interface
6.  
7.   uses
8.     SysUtils, Forms, Controls, StdCtrls;
9.  
10.   type
11.  
12.     { TResourcelessLoginForm }
13.  
14.     TResourcelessLoginForm = class(TForm)
15.     private
16.       LoginButton: TButton;
17.       PasswordEdit: TEdit;
18.       PasswordLabel: TLabel;
19.       procedure LoginButtonClick(Sender: TObject);
20.       procedure SetupGUI;
21.     public
22.       constructor Create; reintroduce;
23.     end;
24.  
25.     function LoginIsCorrectDlg: Boolean;
26.  
27.   implementation
28.  
29.   function LoginIsCorrectDlg: Boolean;
30.   var
31.     dlg: TResourcelessLoginForm;
32.   begin
33.     dlg:=TResourcelessLoginForm.Create;
34.     try
35.       Exit(dlg.ShowModal = mrOK);
36.     finally
37.       dlg.Free;
38.       dlg:=Nil;
39.     end;
40.   end;
41.  
42.   { TResourcelessLoginForm }
43.  
44.   constructor TResourcelessLoginForm.Create;
45.   begin
46.     inherited CreateNew(Nil);
47.     AutoSize:=True;
48.     Caption:='Login';
49.     Position:=poScreenCenter;
50.     BorderStyle:=bsDialog;
51.     SetupGUI;
52.   end;
53.  
54.   procedure TResourcelessLoginForm.LoginButtonClick(Sender: TObject);
55.   begin
56.     if (PasswordEdit.Text = 'LetMeIn') then
57.       ModalResult:=mrOK
58.     else ModalResult:=mrCancel;
59.   end;
60.  
61.   procedure TResourcelessLoginForm.SetupGUI;
62.   begin
63.     PasswordLabel:=TLabel.Create(Self);
64.     with PasswordLabel do begin
65.       AnchorSideLeft.Control:=Self;
66.       AnchorSideTop.Control:=Self;
67.       BorderSpacing.Around:=12;
68.       Caption:='Password:';
69.       Parent:=Self;
70.     end;
71.  
72.     PasswordEdit:=TEdit.Create(Self);
73.     with PasswordEdit do begin
74.       AnchorSideLeft.Control:=Self;
75.       AnchorSideTop.Control:=PasswordLabel;
76.       AnchorSideTop.Side:=asrBottom;
77.       Width:=150;
78.       BorderSpacing.Around:=12;
79.       EchoMode:=emPassword;
80.       PasswordChar:='*';
81.       TabOrder:=0;
82.       Parent:=Self;
83.     end;
84.  
85.     LoginButton:=TButton.Create(Self);
86.     with LoginButton do begin
87.       AnchorSideLeft.Control:=PasswordEdit;
88.       AnchorSideLeft.Side:=asrRight;
89.       AnchorSideTop.Control:=PasswordEdit;
90.       AnchorSideTop.Side:=asrCenter;
91.       AutoSize:=True;
92.       BorderSpacing.Around:=12;
93.       Caption:='LoginButton';
94.       OnClick:=@LoginButtonClick;
95.       TabOrder:=1;
96.       Parent:=Self;
97.     end;
98.   end;
99.  
100. end.

Your .lpr would then need to be as follows:

Code: Pascal  [Select][+][-]

1. program project1;
2.  
3. {$mode objfpc}{$H+}
4.  
5. uses
6.   Interfaces, Forms, Unit1, uResourcelessLoginForm;
7.  
8. {$R *.res}
9.  
10. begin
11.   RequireDerivedFormResource:=True;
12.   Application.Initialize;
13.   if LoginIsCorrectDlg then begin
14.     Application.CreateForm(TForm1, Form1);
15.     Application.Run;
16.   end
17.   else Application.MessageBox('Not allowed in       ','Password protected');
18. end.

[talorigomat]

Thanks Howardpc.  Your example does work.  I wasn't really trying to make a resourceless form.  I had created both forms with the designer so they both have a .lfm resource file, hence I'm not sure why I had this error.

[howardpc]

EResNotFound occurs either because the .lfm resource is not where the compiler expects it, or because it finds it but it cannot read it (or it contains errors or garbage); or, as FTurtle pointed out because you omitted the {$R *.lfm} directive in one of your form units. The latter is unlikely since Lazarus automatically inserts the directive for you whenever you create a new form with File->New Form, so would only happen if you (perhaps) accidentally deleted that source line.