Inno Setup: How can I hide the wizards taskbar icon?

Question

Introduction:
Inno Setup helps me in creating wizards and automated patches for several years now and I am really happy with that compiler. There is barely anything you cannot do with it and the code seems much easier to understand to me than from others (e.g. NSIS, Delphi, etc.).

Question:
What is the code for hiding the entire taskbar icon in Inno Setup 5.x (not just empty icon)?

Background info:
I am well aware that for standard installers this is not needed and would look suspicious. But I talk about those wizards who are part of a bigger installer (they need to have their own due to the way Windows handles environment variables and user group permissions) - imagine it like a container in a container. The outer one is displayed normally, but the inner one should be run "verysilent" even when the user uses it by double-clicking later (most of you already faced this by installing apps as it's not uncommon behaviour). I already managed to hide the setup window by using WizardForm.Hide - but that leaves me without window but still with taskbar icon (looks as unprofessional as a flashing console window on a client would).

What I tried already:

• did online search in general
• did thoroughly search Inno Setup's guide: https://jrsoftware.org
• searched explicit for relevant StackOverflow forum questions (the one targets Delphi does not work for IS)
• searched explicit for relevent SuprerUser forum questions (https://superuser.com/questions/43206/how-can-i-hide-an-application-from-the-windows-taskbar: These tools are not silent and/or cannot implemented in Inno Setup before Form is created)
• tried all Inno Setup parameters (silent, verysilent - it does not hide taskbar icon when executed by double-click)
• tried with some code I found for Pascal/Lazarus online
• simply guessed possible codes based on other commands
• tried alternatives like NSIS, SFX archives (e.g. WinRAR) and VBScript - but all those lacks of the other urgently needed features Inno Setup have
• searched Github repos for external tools that I could implement within Inno Setup
• told IS to restart itself in verysilent mode automatically (don't affect the first double-click generates taskbar icon)
• commands runhidden[Run] / SW_HIDE[Code] affect following instances only as they executed after IS was initialized
• asked ChatGPT - she only tells me how to hide the window form or an icon from systray

What I know so far:

• IS parameters or Inno Setups predefined own functions would not do the trick at all as they would not work on run by double-click
• the taskbar icon is created very early at the beginning of InitializeSetup (even before InitializeWizard) so the user would notice a very quick flashing when insert target code here - the only chance to actually prevent any taskbar icon would be to do this via Preprocessor-Code (if possible).
• I would avoid extern third party tools even there would exist a silent solution: 'Stealing' another programs taskbar icon is a type of code injection and could be easily mixed up with malware, that's not what I want.
• theoretically wrapping is an option (put my installer into another SFX archive that extracts IS and call it with param /VERYSILENT), but that would increase the waiting time for several seconds and seems rather dirty solution to me.

Answer 1

I checked this code on Inno Setup Compiler 6.2.2. It hides the icon from the taskbar. The only note is that the icon appears along with the Message Box showing, for example, "Choosing the installation language".

    [Code]
    var
      function ShowWindow(hWnd: Integer; uType: Integer): Integer;
      external 'ShowWindow@user32.dll stdcall delayload';

      function GetWindowLong(hWnd, nIndex: Integer): Longint;
      external 'GetWindowLongW@user32 stdcall delayload';
    
      function SetWindowLong(hWnd: HWND; nIndex: Integer; dwNewLong: Longint): Longint;
      external 'SetWindowLongW@user32.dll stdcall delayload';

    const
      GWL_HWNDPARENT = (-8);
      GWL_EXSTYLE = (-20);
      WS_EX_TOOLWINDOW = $80;
        
    procedure InitializeWizard();
    var
      hWindow: HWND;

    begin
      hWindow := GetWindowLong(MainForm.Handle, GWL_HWNDPARENT);
      SetWindowLong(hWindow, GWL_EXSTYLE, GetWindowLong(hWindow, GWL_EXSTYLE) or WS_EX_TOOLWINDOW);
      ShowWindow(hWindow, SW_HIDE);
      //CreateCustomPages;
    end;