The bench — Scalos

Why any of this

The Amiga 1200 was the last great Amiga Commodore made, and the desktop people built on it is the one worth having back: Kickstart 3.1, AGA, a hard disk, a graphics card for a screen bigger than the chipset could draw, MUI for modern windows, color icons, and WHDLoad so every game lives on the disk instead of in a box of floppies. An emulator or a MiSTer puts that machine back on your desk. Getting to that finished desktop is the work.

You cannot download it ready-made. Workbench and Kickstart still belong to someone, so the disks and the ROM have to be yours, and Commodore’s own installer has to copy them. Everything after that is a recipe of Proceed buttons, the Green Amiga Alien guide, which people have followed by hand for twenty years. These notes turn that recipe into scripts, so someone new to Amiga emulation gets the upgraded A1200 in an afternoon, from disks they own.

The end of the road is a build nobody babysits. AmiPilot can sit inside the running Amiga, click what is left of the installers, and take a picture of the screen, so an AI agent can check that the desktop came up, that the icons are in color, that a game launches, and fix the script when they are not. Every page here is one step toward that.

Workbench is a program. It is the one that draws the icons and the drawers, and it is started by one line near the end of the Startup-Sequence, LoadWB. Replace that program and you have replaced the desktop while keeping every other part of the operating system, and by the mid-nineties, with Commodore gone and Workbench 3.1 frozen where it was, several people did. Directory Opus 5 was the famous one. Scalos was the one that set out to look and behave exactly like Workbench, only better.

Stefan Sommerfeld wrote it for a small German outfit called ALiENDESiGN, and sold it, briefly, at the end of the nineties. The name is from the Star Trek planet whose inhabitants live so fast they are invisible, and the point was speed: windows that open and scroll without the pauses Workbench takes, icons you can drag while the picture keeps up, drawers that keep listing while you do something else. It reads the same icons, honours the same Tools menu, opens the same windows, and adds a picture in the background, its own palette, a configurable menu, and preferences editors written with MUI.

Scalos is not an operating system, whatever the name says. It is the program that draws the desktop, swapped for a better one.

In October 1999 Sommerfeld said he was stopping, with a promise to release the source; a month later a group called Satanic Dreams Software took it over, and versions 1.1 and 1.2 went out as freeware in 2000. The source was opened in 2012 and it still builds for 68k, PowerPC and AROS. Version 1.2b, the freeware one the guide points at, is what is on this disk.

A 640 by 480 WinUAE desktop with a small Scalos window in the top-left corner containing only the Ram Disk icon. — The problem, in WinUAE. Scalos has started, as the title bar says, but as a window about 200 by 100 pixels, with the rest of the screen empty behind it.

The same small Scalos window on the MiSTer’s 1280 by 720 screen. — The same on the board. The Backdrop toggle in the menu fixes it for the session and forgets it at the next boot.

The window in the corner

Both pictures on the right show the first thing every Scalos install on this disk did: come up as a window. Workbench has a menu item, Backdrop, that turns the root window into the screen itself, and Scalos has the same item in the same place. Tick it and the desktop is right until you reset, when it is a window again. The obvious place to look is Scalos.prefs, the file its own preferences program writes, and nothing in there says backdrop.

The answer was Workbench’s. Workbench keeps its own state in ENVARC:Sys/wbconfig.prefs, and Scalos, being a faithful replacement, reads that file for the backdrop flag. Workbench 3.1 writes a version 0 of it that Scalos ignores; what Scalos wants is version 1 with the flag 0x00010000 set, and the Backdrop menu item in Scalos does not write it. Nothing does, on a stock disk. So the mint writes it, and the finished-disk check decodes the flag rather than trusting the filename. Since then the first boot has been a backdrop every time, and AmiPilot checks it on every restart: a backdrop root window has no title, so if the window list comes back without a Workbench-titled window and with the Scalos screen open, the desktop came up right.

The other thing Scalos owns is the colours of pens 4 to 7 on its screen, which is why the MagicWB icons needed two palette files: Workbench’s for the first four pens and Scalos’s Palette.prefs for the next four. Both are written by the same installer from the same eight colours.

A drawer open on a Scalos backdrop: MagicWB grey background, colour icons. — What it looks like when the file is right. Scalos as the backdrop, MagicWB grey on all eight pens, a drawer opened by its own opendrawer tool for the capture.

The two editors

Scalos keeps its settings in two programs, both MUI. Scalos in the Prefs drawer has the pages the installer chapter walks through: Icons, Bobs, Titles, TextMode, Paths, Default Sizes, PlugIns, Miscellaneous, NewIcons. Scalos Palette is the colour table, the window whose saved file was taken apart in Eight pens. Neither has a button AmiPilot can press, for the reason on the MUI page, but both have a Project menu with Quit on it, and that was enough to open each one, take its picture and close it from a script. The pictures below are the first thing AmiPilot did to these windows that was not a screenshot of them being ignored.

Scalos preferences, About page, on the acceptance disk. Version 1.2, and the credit that says who wrote it.

The Scalos Palette window: a table of eight pens with red, green and blue values, a colour wheel, sliders, New, Delete, WBColors and Pen Adjust buttons. — Scalos Palette with the MagicWB table the build wrote: 149 149 149, black, white, 59 103 162, 123 123 123, 175 175 175, 170 144 124. The colour wheel and the gradient slider are the two gadgets in this window AmiPilot can name, because they are Commodore’s BOOPSI classes, not MUI’s.

What the scripts and AmiPilot took over

Chapter 9 of the guide is Scalos. It is the longest chapter after Workbench itself, because Scalos has an installer, an assign, a menu to import and settings to save. Where each step went.

Automated
Fetch
Download Scalos into Programs.
fetch_archives.sh pulls the 1.2b archive.
Eliminated
Boot, Shell
Reload WinUAE, Shell, lha x, endcli.
7z on the host.
Automated
Install
Run the installer: Expansion drawer, replace LoadWB, add the assign, a dozen Proceeds.
install_scalos.sh puts Scalos in SYS:Expansion/Scalos, swaps C:LoadWB for the Scalos starter, adds the Scalos: assign to S:User-Startup, and refuses to run unless MUI is already on the disk. Called by setup_winuae.sh --scalos and build_mister_image.sh.
Automated
Menu
Open Scalos Prefs, import the menu, Save.
The saved menu file is written onto the disk by the installer.
Automated
Backdrop
Tick Backdrop in the menu on every boot, or find out about wbconfig.prefs.
write_wbconfig_prefs.py writes the version 1 file with the backdrop flag, and the installer puts it in ENVARC:Sys. First boot is a backdrop.
Automated
Palette
Set the MagicWB colours in Scalos Palette, Save.
write_scalos_palette_prefs.py writes ENVARC:Scalos/Palette.prefs from the Scalos source’s own format, alongside Workbench’s palette.prefs, both from one table of eight colours. --palette none skips them.
Once
Reset
Reset so Scalos starts instead of Workbench.
The first boot of the new disk.
Automated
Check
Look at the desktop.
check_guide_hdf.sh decodes wbconfig.prefs and the Scalos palette on the finished hardfile. verify_winuae_desktop.sh --require-backdrop restarts WinUAE and has AmiPilot confirm Scalos came up as the backdrop on its own. show_drawer.sh opens a drawer through Scalos’s own Tools/opendrawer, because a backdrop has no window title for AmiPilot to address.

Steps follow Chapter 9 of the Green Amiga Alien guide; the ledger for it is here. History from Sommerfeld’s October 1999 statement to amiga-news.de and the Scalos project. The words are ours.