How to decompress archive file with progress and cancel button in Inno Setup using unarc

I am using this code: How to add .arc decompression to Inno Setup? (answer of Martin Prikryl). I want to add a cancel button at decompressing page and active this page for others functions (when the decompression is active, this page is inactive and, for example, i can not press on/off button of my music implementation).

How to add a cancel button to decompression page? and how to active this page for others functions?

I have reimplemented the solution from How to add .arc decompression to Inno Setup? using unarc.dll (from FreeArc+InnoSetup package ISFreeArcExtract v.4.0.rar).

It greatly simplifies the code and also makes it easier to add the ability to cancel the decompression.

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#define ArcArchive "test.arc"

[Files]
Source: unarc.dll; Flags: dontcopy

[Code]

const
  ArcCancelCode = -10;

function FreeArcExtract(
  Callback: LongWord;
  Cmd1, Cmd2, Cmd3, Cmd4, Cmd5, Cmd6, Cmd7, Cmd8, Cmd9, Cmd10: PAnsiChar
  ): Integer;
  external 'FreeArcExtract@files:unarc.dll cdecl';
  
const
  CP_UTF8 = 65001;

function WideCharToMultiByte(CodePage: UINT; dwFlags: DWORD;
  lpWideCharStr: string; cchWideChar: Integer; lpMultiByteStr: AnsiString;
  cchMultiByte: Integer; lpDefaultCharFake: Integer;
  lpUsedDefaultCharFake: Integer): Integer;
  external 'WideCharToMultiByte@kernel32.dll stdcall';

function GetStringAsUtf8(S: string): AnsiString;
var
  Len: Integer;
begin
  Len := WideCharToMultiByte(CP_UTF8, 0, S, Length(S), Result, 0, 0, 0);
  SetLength(Result, Len);
  WideCharToMultiByte(CP_UTF8, 0, S, Length(S), Result, Len, 0, 0);
end;

var
  ArcTotalSize: Integer;
  ArcExtracted: Integer;
  ArcCancel: Boolean;
  ArcProgressPage: TOutputProgressWizardPage;

function FreeArcCallback(
  AWhat: PAnsiChar; Int1, Int2: Integer; Str: PAnsiChar): Integer;
var
  What: string;
begin
  What := AWhat;
  if What = 'origsize' then
  begin
    ArcTotalSize := Int1;
    Log(Format('Total size of files to be extracted is %d MB', [ArcTotalSize]));
  end
    else
  if What = 'write' then
  begin
    if ArcTotalSize > 0 then
    begin
      ArcProgressPage.SetProgress(Int1, ArcTotalSize);
    end;
    ArcExtracted := Int1;
  end
    else
  begin
    // Just to pump message queue more often (particularly for
    // 'read' callbacks), to get more smooth progress bar
    if (ArcExtracted > 0) and (ArcTotalSize > 0) then
    begin
      ArcProgressPage.SetProgress(ArcExtracted, ArcTotalSize);
    end;
  end;

  if ArcCancel then Result := ArcCancelCode
    else Result := 0;
end;

function FreeArcCmd(
  Cmd1, Cmd2, Cmd3, Cmd4, Cmd5, Cmd6, Cmd7, Cmd8, Cmd9, Cmd10: string): Integer;
begin
  ArcCancel := False;
  try
    Result :=
      FreeArcExtract(
        CreateCallback(@FreeArcCallback),
        GetStringAsUtf8(Cmd1), GetStringAsUtf8(Cmd2), GetStringAsUtf8(Cmd3),
        GetStringAsUtf8(Cmd4), GetStringAsUtf8(Cmd5), GetStringAsUtf8(Cmd6),
        GetStringAsUtf8(Cmd7), GetStringAsUtf8(Cmd8), GetStringAsUtf8(Cmd9),
        GetStringAsUtf8(Cmd10));

    Log(Format('Arc command "%s" result %d', [Cmd1, Result]));
  except
    Result := -63;
  end;
end;

function UnPackArchive(ArchivePath: string; DestPath: string): Integer;
begin
  // Find out length of files to be extracted - origsize
  Result := FreeArcCmd('l', '--', ArchivePath, '', '', '', '', '', '', '');

  if Result = 0 then
  begin
    // Actually extract
    Result :=
      FreeArcCmd('x', '-o+', '-dp' + DestPath, '-w' + DestPath, '--',
                 ArchivePath, '', '', '', '');
  end;
end;

procedure UnpackCancelButtonClick(Sender: TObject);
begin
  ArcCancel := True;
end;

procedure ExtractArc;
var
  ArcArchivePath: string;
  UnpackResult: Integer;
  PrevCancelButtonClick: TNotifyEvent;
  Error: string;
begin
  ArcProgressPage :=
    CreateOutputProgressPage('Decompression', 'Decompressing archive...');
  ArcProgressPage.SetProgress(0, 100);
  ArcProgressPage.Show;
  try
    WizardForm.CancelButton.Visible := True;
    WizardForm.CancelButton.Enabled := True;
    PrevCancelButtonClick := WizardForm.CancelButton.OnClick;
    WizardForm.CancelButton.OnClick := @UnpackCancelButtonClick;

    ArcArchivePath := ExpandConstant('{src}\{#ArcArchive}');
    Log(Format('Arc extraction starting - %s', [ArcArchivePath]));

    ArcExtracted := 0;
    UnpackResult := UnPackArchive(ArcArchivePath, ExpandConstant('{app}'));

    if UnpackResult <> 0 then
    begin
      if ArcCancel then
      begin
        Error := 'Extraction cancelled';
      end
        else
      begin
        Error := Format('Extraction failed with code %d', [UnpackResult]);
      end;

      MsgBox(Error, mbError, MB_OK);
    end;
  finally
    Log('Arc extraction cleanup');
    ArcProgressPage.Hide;
    WizardForm.CancelButton.OnClick := PrevCancelButtonClick;
  end;
end;

procedure CurStepChanged(CurStep: TSetupStep);
begin
  if CurStep = ssPostInstall then
  begin
    ExtractArc;
  end;
end;

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For CreateCallback function, you need Inno Setup 6. If you are stuck with Inno Setup 5, you can use WrapCallback function from InnoTools InnoCallback library.

---

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The code extracts a separate .arc file. If you want to embed the archive to the installer, you can use

[Files]
Source: {#ArcArchive}; DestDir: "{tmp}"; Flags: nocompression deleteafterinstall

And extract the archive from the {tmp}:

ArcArchivePath := ExpandConstant('{tmp}\{#ArcArchive}');

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Note that the unarc.dll from ISFreeArcExtract v.4.0.rar does not seem to support password protected archives. The version from ISFreeArcExtract v.4.2.rar does, but I'm not aware of trustworthy download link.

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If you want to extract multiple archives, see Inno Setup - How to add multiple arc files to decompress?