Application start-up

Before a user's application takes control, there's some stuff happening under Launchpad control. Here's a brief description of the start-up process for people interested in the inner details.

In Pharo, Launchpad is implemented as a command-line handler, taking control when the launchpad command is found in the command line.

In VAST Platform, there's no such thing as a command-line handler. To achieve a similar effect, the user needs to use LaunchpadCommandLineHandler activate as the applicationLaunchCode in their packaging instructions.

Once the command-line handler is activated, the first thing it does is to set up the logging infrastructure:

• In Pharo, [INFO] records output to stdout. [WARNING] and [ERROR] records output to stderr.
• In VAST Platform, every record outputs to TranscriptTTY (this ends up at stdout on Unix); because there's no way to access the stderr handle attached to the VM process.

As a second step, it instantiates a LaunchpadApplicationStartingContext with the command-line and a reference to stdout. This context is later available in all the required methods and ultimately accessible by the application in its basicStartWithin: method.

After that, a LaunchpadRootCommand is created and evaluated within the context. First this command tries to handle any root option and then find which sub-command to evaluate. Once the start sub-command is found, LaunchpadStartApplicationCommand takes control.

The start command will first process any option and then search for an application with the provided handle. If there's no application matching, it will emit an error and exit. If an application is found:

• Instantiate it with the corresponding mode and configuration provider
• Set it as the currently running application
• Give control to the application itself

Applications first load and log their configuration. If successful, they send the basicStartWithin: message to themselves. Here's where the user-defined code for the application starts to execute.