Can Inno Setup respond differently to a new install and an update? - inno-setup

Question

My InnoSetup script opens a web page (with the user's default browser) at the end of the install process:
[Run]
Filename: http://example.com; Flags: shellexec
However, I'd like the web page to not be opened if the app already exists, i.e., if the user is installing a new version of the program. The web page should only be opened after the initial install. (I assume it's worth mentioning that the install includes an AppID, obviously, and enters values in the registry beside installing files.)
Thank you, as always -- Al C.

Answer 1

Yes, this is easy to do with scripting.
Just write
[Run]
Filename: "http://example.com"; Flags: shellexec; Check: NotAnUpdate
procedure CurPageChanged(CurPageID: Integer);
begin
if CurPageID = wpInstalling then
IsUpdate := FileExists(ExpandConstant('{app}\TheFileNameOfMyApp.exe'));
end;
function NotAnUpdate: Boolean;
begin
result := not IsUpdate;
end;

Answer 2

The answer by #AndreasRejbrand won't work, if user chooses to install the executable to a different location than the last time.
You can query installer-specific Inno Setup registry keys:
#define AppId "your-app-id"
#define SetupReg \
"Software\Microsoft\Windows\CurrentVersion\Uninstall\" + AppId + "_is1"
#define SetupAppPathReg "Inno Setup: App Path"
[Setup]
AppId={#AppId}
...
[Run]
Filename: "https://www.example.com/"; Flags: shellexec; Check: not IsUpgrade
...
[Code]
function IsUpgrade: Boolean;
var
S: string;
begin
Result :=
RegQueryStringValue(HKLM, '{#SetupReg}', '{#SetupAppPathReg}', S) or
RegQueryStringValue(HKCU, '{#SetupReg}', '{#SetupAppPathReg}', S);
end;
For an example how to use IsUpgrade in [Code] section, see
Excludes part of Code section in ssPostInstall step if installation is update in Inno Setup
Check this if your "AppId" contains a left-curly-bracket:
Checking if installation is fresh or upgrade does not work when AppId contains a curly bracket