Cassio

A nice but old Othello program, revisited?

The current state of Cassio (June 2021)

The source code for Cassio 8.4 is a huge set (~400.000 lines) of Pascal code, cross-compiling to x86-64 using GNU Pascal on the Macintosh, where GNU Pascal was running as a plug-in for Metrowerks CodeWarrior, which is a PowerPC binary. Cassio uses the Quickdraw/Carbon library by Apple for the user interface and other OS-related stuff.

The current situation is that Cassio development is dead, because:

1. Compiler: the GNU Pascal compiler is no longer maintained since 2005
2. Workflow: CodeWarrior does not run on new Macs because Apple has dropped support for PowerPC emulation (Rosetta) in MacOS X 10.7 in 2010
3. Execution: Cassio itself has stopped working on newer Mac in 2020 because Apple has decided that Quickdraw/Carbon programs could no longer be run in MacOS X 10.14.

What follows is a tentative plan to port Cassio to newer technologies.

It would be a nice bonus if Cassio became cross-platform at the same time (MacOS, Windows, Linux) 😊

Choosing the tools

I would like to keep the Pascal codebase, because rewriting everything in C++ or in Python would take me another lifetime. Given this constraint, we address the points of the previous section like so:

1. Compiler: the most active Pascal compiler at the moment is FreePascal ( http://https://www.freepascal.org )
2. Workflow: no longer project IDE, everything from the command line + Github for versioning system + new code in Python for portability.
3. Graphic library: I would like to define a pure text protocol, so that Cassio is able to use its standard input/output to talk to a minimal graphic library emulating the behavior of the simple Quickdraw graphic primitives of 1984 (windows, menus, mouse, dialogs, drawing text, drawing jpeg, sound, and that's about all I need).

Preliminary work: implementing an abstract graphical protocol

• The minimal graphic library could be written in Python, using the PyQt bridge to Qt4. This is quite portable, as Python and Qt are available everywhere. See the carbon.py file for the current state of the library.
• The text protocol could be similar to the examples in torture.txt, for instance. The protocol has the same flavor as The Othello Engine Protocol already used in Cassio for Cassio<->engine communications.
• Cassio would have to be able to connect to the standard input/output in an efficient way, as there may be thousands of graphic primitives per second.

Installing the necessary compilers and librairies

To build Cassio, you will need a recent version of the FreePascal compiler and a working Python 3 environment with the PyQt4 module. The PyQt4 module provides the necessary interfaces to use Qt4 from Python 3.

General instructions for installation:

• FreePascal: see the instructions on the FreePascal wiki
• Python 3: see https://www.python.org/downloads/
• PyQt4: see https://doc.qt.io/archives/qt-4.8/installation.html

Installing Python 3 (short version)

Follow the instructions on https://www.python.org/downloads/

Installing the FreePascal compiler for MacOS (short version)

• Make sure that you already have XCode downloaded from the App Store
• Install the FreePascal compiler version 3.2.0 (or later), for instance with one of the following commands:

brew install fpc   (for Homebrew)
port install fpc   (for Macports)

Installing PyQt4 for MacOS (short version)

• Make sure that you already have XCode downloaded from the App Store
• Download PyQt4, for instance with one of the following commands:

pip3 install pyqt4 pyqt4-tools     (for pip3)
brew install pyqt4                 (for Homebrew)
port install py39-qtpy4            (for MacPorts)

• Check that PyQt downloaded properly by opening up the Python3 interpreter and typing the following command:

import PyQt4.QtGui

TODO: suggestions welcome for short instructions on how to install FreePascal+ Python3+PyQt4 on Windows or Linux

References

Possible sources for inspiration (in no particular order)

• The FreePascal website: https://www.freepascal.org
• The Qt4 documentation: https://doc.qt.io/archives/qt-4.8/installation.html
• A Qt4 tutorial: https://zetcode.com/gui/pyqt4/
• https://courspython.com
• Ingemar Ragnemalm in Trabskell 5 has the file QDCG.pas, which is quite a complete reference for the obsolete QuickDraw API from Apple. Probably a bit overkill for my needs, probably, but still useful. https://twokinds.se/yh/transskel5/
• Roland Chastain has written several chess programs (both chess engines and chess graphical user interfaces) in FreePascal. Quite active, and he speeks french! His Github is a good central place for Pascal chess-related stuff: https://github.com/rchastain