How to force Inno Setup to set the installation folder dynamically with info from custom wizard page?

Question

In Inno Setup I added a custom wizard page where the user can enter a suffix code that shall be added dynamically to the default directory.

Standard DefaultDirName is c:\MyApp. When the user adds a suffix 01 in an extra custom wizard page the DefaultDirName should change to c:\MyApp01.

How can this be done? Obviously I cannot use code in the [Setup] section because the code is evaluated prior to any wizard page.

Answer 1

When leaving your "suffix" page, append the suffix to the installation path.

Additionally you have to deal with:

• user going back to the suffix page and changing the suffix
• re-installations (upgrades) - my solution just does not allow changing suffix for re-installations (relying on the default Inno Setup behavior, where user has a little chance to change installation path).

#define AppId "your-app-id"
#define SetupReg "Software\Microsoft\Windows\CurrentVersion\Uninstall\" + AppId + "_is1"
#define SetupAppPathReg "Inno Setup: App Path"

[Setup]
AppId={#AppId}

[Code]

function IsUpgrade: Boolean;
var S: string;
begin
  Result :=
    RegQueryStringValue(HKLM, '{#SetupReg}', '{#SetupAppPathReg}', S) or
    RegQueryStringValue(HKCU, '{#SetupReg}', '{#SetupAppPathReg}', S);
end;

var
  SuffixPage: TInputQueryWizardPage;

procedure InitializeWizard();
begin
  if not IsUpgrade then
  begin
    SuffixPage := CreateInputQueryPage(wpWelcome, 'Select suffix', '', '');
    SuffixPage.Add('Suffix', False);
  end;
end;

function NextButtonClick(CurPageID: Integer): Boolean;
begin
  // Add suffix to path, when leaving "suffix" page
  if (SuffixPage <> nil) and (CurPageID = SuffixPage.ID) then
  begin
    WizardForm.DirEdit.Text := WizardForm.DirEdit.Text + SuffixPage.Values[0];
  end;
  Result := True;
end;

function BackButtonClick(CurPageID: Integer): Boolean;
var
  Suffix: string;
  P: Integer;
begin
  // When going back from "select dir" page
  if (CurPageID = wpSelectDir) and (SuffixPage <> nil) then
  begin
    Suffix := SuffixPage.Values[0];
    P := Length(WizardForm.DirEdit.Text) - Length(Suffix) + 1;
    // ... and the path still contains the suffix
    // [was not edited out by the user] ...
    if Copy(WizardForm.DirEdit.Text, P, Length(Suffix)) = Suffix then
    begin
      // ... remove it from the path
      WizardForm.DirEdit.Text := Copy(WizardForm.DirEdit.Text, 1, P - 1);
    end
      else
    // if the suffix was edited out by the user, clear suffix box
    begin
      SuffixPage.Values[0] := '';
    end;
  end;
  Result := True;
end;