velopack/specs/Installer.md

Installer

The installer consists of two parts: Setup.exe (C++ bootstrapper) and Update.exe (C# Squirrel Client). There are several main design goals of the installer:

• Run as quickly as possible, with as little user interface interaction as possible. The faster we can get into the application, the better. An ideal install experience is that once Setup.exe gets clicked, within 3sec the application is running on the user's machine. Double-clicking Setup.exe should feel like clicking the app shortcut.

• Setup.exe should be written such that it does as little work as possible, because C++.

• Running an older Setup.exe should simply execute the current app.

• Support installation of non-C# applications

Setup.exe

Setup.exe does the following operations:

1. Determines if the .NET Framework is installed
2. If not, relaunches itself with /installfx45, which opens a progress dialog which downloads the .NET Framework and silently invokes it.
3. Extract Update.exe and AppName-full.nupkg to %LocalAppData%\Squirrel\Temp which are embedded as resources.
4. Execute Update.exe with the /install switch, and apply any switches that were applied to Setup.exe
5. Nuke the extracted temporary files from step 3.

Update.exe

Update.exe is a generic client for Squirrel which supports several operations:

• --install [directory] [/silent] - Install the NuPkg file given (or any NuPkg files in the same directory as itself), and launch their applications. If /silent is given, don't launch anything. Copy Update.exe to the application root directory. Install also writes an entry in Programs and Features which will invoke /uninstall.
• --uninstall - Completely uninstall the application associated with the directory in which Update.exe resides.
• --download URL - Check for updates from the given URL and write information about available versions to standard output in JSON format.
• --update URL - Updates the application to the latest version from the remote URL

Sample JSON output

{
    currentVersion: "1.0.0.0",
    futureVersion: "1.0.0.1",
    releasesToApply: [
        {
            version: "1.0.0.1",
            releaseNotes: "This does a thing"
        }
    ]
}