form visible already true ???

Can you translate to English please.

errror msg: "....   from a visible window you can not change to a modal window " 

it's possible events inside the form to show modal cause it to become visible
before the call to showmodal is called

best solution:
find the code which sets the form onscreen
(like application.processmessages)

workaround:
hide the form before showmodal

form := Tform.Create(self)
try    
  form.Hide;
  form.showmodal;
  if form.modalresult = mrOK then
  begin

  end
finally
  form.Free;
end;

What is your code? I can successfully use this code:

procedure TForm1.Button1Click(Sender: TObject);
var
  form : Tform;
begin
  form := Tform.Create(self);
  form.showmodal;
  if (modalresult=mrOK) then
  begin

  end;
  form.Free;
end;

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@jimxy : exactly my code ... used many times on other locations without a problem

@geerd : help to show the form butr still av at modual result

set form visible property to false in design
and try again

show the code in formcreate, constructor create, formshow, aftercreate and anything you call from those 4 procs/events

---  no more code --- i promise except ....

procedure TForm.FormCreate(Sender: TObject);
begin
     
    // fDBList :=TDatabaseList.create;    //  more info seee   https://www.experts-exchange.com/Programming/Languages/Pascal/Delphi/Q__26825062.html 

     self.height   :=  Default_Height;

     self.Width    := Default_Width;

     scaled := true;
end;


and ...  I work with a TObjectist... once finished my work with the list a Button on that from disappears ....  never set the property visible to false (i can also promise)

changing the width or height will cause an invalidate
which in turn causes your form to become visible :)

procedure TForm.FormCreate(Sender: TObject);
begin
     self.height   :=  Default_Height;
     self.Width    := Default_Width;
     scaled := true;
     visible := false;
end;

or set the width and height in the constructor

try to use  

 (self as Tform).height  :=  Default_Height;
 (self as TForm).Width  := Default_Width; 

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self is in this case of type TForm, that wouldn't make a difference

Where did you get procedure TForm.FormCreate(Sender: TObject);? Why just TForm?

something else in your code is causing the problem

i created a test sample and this doesn't have the problem:
 

unit Unit1;

interface

uses
  Windows, Messages, SysUtils, Variants, Classes, Graphics, Controls, Forms,
  Dialogs, StdCtrls, Buttons;

type
  TForm1 = class(TForm)
    BitBtn1: TBitBtn;
    Edit1: TEdit;
    procedure BitBtn1Click(Sender: TObject);
  end;

var
  Form1: TForm1;

implementation

uses Unit3;

{$R *.dfm}

procedure TForm1.BitBtn1Click(Sender: TObject);
begin
  if ShowForm3(Self) then
    Edit1.Text := 'Ok'
  else
    Edit1.Text := 'oops';
end;

end.

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unit Unit3;

interface

uses
  Windows, Messages, SysUtils, Variants, Classes, Graphics, Controls, Forms,
  Dialogs;

type
  TForm3 = class(TForm)
    procedure FormCreate(Sender: TObject);
  private
  public
  end;

var
  Form3: TForm3;

function ShowForm3(AOwner: TComponent): boolean;

implementation

{$R *.dfm}

function ShowForm3(AOwner: TComponent): boolean;
var form: TForm3;
begin
  Result := False;
  form := TForm3.Create(AOwner);
  try
    if form.ShowModal = mrOk then
    begin
      Result := True;
    end;
  finally
    form.Free;
  end;
end;

procedure TForm3.FormCreate(Sender: TObject);
begin
  Width := 200;
  Height := 300;
  Scaled := True;
end;

end.

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ow ow ow ... you override the standard TForm ?
with your own class TForm ?

so you subclassed the TForm ?
and want to add your own customizing ?

nope , still works with subclassing

unit Unit3;

interface

uses
  Windows, Messages, SysUtils, Variants, Classes, Graphics, Controls, Forms,
  Dialogs;

type
  TForm = class(Forms.TForm)
  public
    constructor Create(AOwner: TComponent); override;
    procedure FormCreate(Sender: TObject);
  end;

type
  TForm3 = class(TForm)
  end;

var
  Form3: TForm3;

function ShowForm3(AOwner: TComponent): boolean;

implementation

{$R *.dfm}

function ShowForm3(AOwner: TComponent): boolean;
var form: TForm3;
begin
  Result := False;
  form := TForm3.Create(AOwner);
  try
    if form.ShowModal = mrOk then
    begin
      Result := True;
    end;
  finally
    form.Free;
  end;
end;

{ TForm }

constructor TForm.Create(AOwner: TComponent);
begin
  inherited Create(AOwner);
  OnCreate := FormCreate;
end;

procedure TForm.FormCreate(Sender: TObject);
begin
  Width := 200;
  Height := 300;
  Scaled := True;
end;

end.

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You can assign the ModalResult to a variable or just test it directly
 var
     form: Tform
  form := Tform.Create(self);
  try
    if form.ShowModal = mrOk then
  .........

or
  var
     FormResult: Integer;
      form: Tform;
  begin
     form := Tform.Create(self);
     try
       FormResult := form.ShowModal;
       ..............
 
 
 

OK:  Geerd idea so far a bit improvement  on other pc the same code with a different run time behaviour,
means  only the missing button effect appears ......

the very bad thing :  the complete code had been functional a few month ago ....     but we did not track the changes with subversion of that unit :-(

is this delphi 7 on a new pc showing the different behaviour ?

and you have also installed the patches for delphi 7 on the new pc ?

no both PC (notebook) are almost identical , could not see any difference in the D7 behaviour -  no idea where this bug comes from ....

it's easy to test a delphi... most common bug is oldcreateorder

this comes into play with a constructor and FormCreate

var Test: integer;

constructor TForm1.Create(AOwner: TComponent);
begin
  Test := 1;
  inherited Create(AOwner);
  ShowMessage('Create '  + IntToStr(Test));
  Test := Test +1;
end;

procedure TForm1.FormCreate(Sender: TObject);
begin
  ShowMessage('FormCreate ' + IntToStr(Test));
  Test := Test + 10;
end;

you should get Create 1, and then get FormCreate 2
with oldCreateOrder := False
otherwise the delphi version has the bug

at least that's what i found out some time ago with a unpatched delphi 7

oh yeah: the type declaration

type
  TForm1 = class(TForm)
    procedure FormCreate(Sender: TObject);
  public
    constructor Create(AOwner: TComponent); override;
  end;

add fastrMM4 and removed code from the project file now compile is failing with AV ??????

you forgot to blank out the other module name ... LayoutExtraction

Start the program with F8 in delphi.
Then in the menu search / Find error
enter 004AFF6A and see where it takes you ...

you are now giving a completely different error
????????????????????????

and then deleting this question because you found the solution to that other error
thud ... my chin dropping on the floor in awe and staring wide eyed at my screen


 

+++
___ooo__0_0__ooo___

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seems that a BDE failure has been the reason, therfore it does not make sense to me to abward the good discussion from yetserday, next time I spilt points again ...