Inno Setup Disable close button (X)

Question

How to disable the Close button (borderstyle)?

I want to combine that with hiding "About Setup" command from system menu:
Inno Setup - BorderIcons dropdown menu

Answer 1

Use EnableMenuItem WinAPI function:

function GetSystemMenu(hWnd: THandle; bRevert: Boolean): THandle;
  external '[e-mail] stdcall';

function EnableMenuItem(hMenu: UINT; uIDEnableItem, uEnable: UINT): Boolean;
  external '[e-mail] stdcall';

const
  MF_GRAYED = $1;
  MF_BYCOMMAND = $0;
  SC_CLOSE = $F060;

procedure DisableCloseButton;
var
  Menu: THandle;
begin
  Menu := GetSystemMenu(WizardForm.Handle, False);
  EnableMenuItem(Menu, SC_CLOSE, MF_BYCOMMAND or MF_GRAYED);
end;

You have to call the DisableCloseButton later than from the InitializeWizard event function.

There maybe a better place to call it, but for a simplicity you can call it from CurPageChanged:

procedure CurPageChanged(CurPageID: Integer);
begin
  DisableCloseButton;
end;

But note that you need to keep the code to hide "About Setup" command in InitializeWizard as that needs to be called only once (and it works there correctly).

The screenshot shows both codes combined: