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# The Installer program

The latest pre-V44 release of the `Installer` was V43.2, distributed on the Amiga Technologies FTP site.

## Checking the Installer version

If your installation script uses new features not available in earlier versions of the `Installer`, it is important to check the variable @installer-version before using these new features. This variable will default to 0 with old versions of `Installer` like V1.24, so it is safe and easy to check. Please do not do an exact equality check. Check for a minimum revision, just like with libraries.

## Backtracing

Starting with V44 the `Installer` allows backtracing in your script. If you use this mechanism the `Abort Install` button is replaced with a `Back` button in most cases. You should define a `(back)` parameter for all statements and functions with user interaction that presents the `Back` button. If you don't the `Back` button is disabled which may frustrate the user. The following new commands support backtracing:

`(trace)`
  The trace statement sets an backtrace position. A retrace will continue on that position in the script.
`(retrace)`
  The retrace initiates the backtrace mechanism. It skips the last backtrace position and searchs for the previous one.
`(back <code>)`
  If the user press the `Back` button the code is executed. Typically this code will contain a `(retrace)` statement the last statement.

Please see the ``Installer.guide'` for a detailed description of these commands.

## Interaction with the Workbench

The V44 `Installer` provides a way for installation scripts to interact with the Workbench. The following commands are new in V44:

`(openwbobject <argument> ...)`
  Open a Workbench object which can be a disk, a drawer, a trashcan, a tool or a project.
`(showwbobject <argument>)`
  This statement scrolls the view of an workbench drawer until the named icon is visible. The drawer has to be opened before.
`(closewbobject <argument>)`
  This statement closes the named workbench object. Currently only disks, trashcans and drawers can be closed.

## Multimedia support

The V44 `Installer` provides support for displaying text and pictures and playing sounds during the installation. It is also possible to have the `Installer` open on its own screen to provide a full screen backdrop for the installation. The OS 3.5 installer script makes use of these new features to provide an eye pleasing installation procedure as well as showing the user license in a separate window. Before V44, some later installation scripts from third party applications already made use of external programs to obtain similar results. It is recommended that you adapt your existing scripts to use the new mechanisms built into the Installer for increased consistency between different products.

The following multimedia commands are provided by the V44 `Installer`:

`(effect <position> <effect> <color 1> <color 2>)`
  Sets the graphical effect that is used for the background.
`(showmedia <medianame> <filename> <position> <size> <borderflag> ...)`
  showmedia opens a datatype and presents it to the user.
`(setmedia <media> <action> [parameter])`
  Using the setmedia statement some action can be performed on the datatype.
`(closemedia <media>)`
  Closes a media file and removes it from memory.

Please see the ``Installer.guide'` for a detailed description of these commands.

## Rebooting the System

One new command allows to reboot the system automatically once the installation has finished. This command should be used with extreme caution: forced reboots are extremely annoying to most users.

`(reboot)`
  This commands reboots the Amiga.

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