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Viola is a Z-Machine Interpreter written in Python.

Python 100.00%

python z-machine

viola's Introduction

VIOLA 0.8.1

Written by David Fillmore.

Viola is a Z-Machine Interpreter. That is, it interprets programs written for the virtual
machine known as the Z-Machine. There's a brief history of the Z-Machine at the bottom of
this file, for some reason.

The latest code for Viola is available at https://github.com/DFillmore/viola.

FEATURES

* Z-Machine Versions 1-8 support
* Z-Machine Standards Document 1.1 compliance
* Blorb Resource Format 2.0 compliance
* Quetzal Saved Game Format 1.4 compliance
* Support (via Blorb) for sounds and, in Version 6, images.

INSTALLATION

Some brief notes on getting the program up and running.

You will need Python 3 (I use version 3.3.5), which you can get at http://www.python.org, and
pygame (I use version 1.9.2), which you can get at http://www.pygame.org/. I genuinely don't
know if the setup.py file does anything useful.

BRIEF HISTORY OF THE Z-MACHINE FOR SOME REASON

The Z-Machine was created in the early Eighties by Infocom in order to run
text adventures.

Infocom evolved the design of the Z-Machine gradually, and created six distinct versions,
each with more capabilites than the previous. Versions 1, 2 and 3 are almost identical,
with slight changes to certain parts of the design that make them incompatible. Most of
Infocom's games were released for version 3. Version 3 was a fairly simple design, but a
seperate upper window was introduced for one game, and support for sound effects (which
was really part of the Version 5 design, but a scaled down version was stuck into Version
3).
Version 4 introduced text styles, better upper window support and a few other features,
as well as allowing games to be larger. Version 5 allowed even larger games, with several
new features including better sound support. Version 6 allowed for graphics, up to eight
windows which could be moved and resized, bigger games, and other less obvious features.

Then Infocom went out of business, more or less.

Several years later, Graham Nelson created Inform, which allowed anyone to create
Z-Machine games. Two new Versions were created, numbered 7 and 8. These have none of the
extra features of z6, but instead are identical to the z5 model, except that they both
allow larger games. z7 was never really used.

Most games created for the Z-Machine since Infocom stopped business are z5 games.

viola's People

Contributors

Stargazers

Watchers

Forkers

mseyne zenpan

viola's Issues

Lost Pig starts in wrong room

Saving crashes the interpreter

Some old code from back when Viola used wxPython is called to make a file dialog, but this does not make sense to pygame.

Deleted input text is not entirely deleted

Transcription should allow you to choose the filename

Control error message frequency from command line options

Better Unicode support

Games should be able to print as many Unicode characters as possible

Settings file should allow colour selection

Sound interrupt routines circumvent quit

If the interpreter is at the 'press any key to quit' prompt, and a sound is still playing, when the sound finishes it can call the interrupt routine, which will start the game running again.

z6 operation to get pixel colour does not work properly

It should be possible to get the colour of the pixel under the cursor. If this is one of the basic colours that the Z-Machine understand, the colour data for the current window should be set to the value of that basic colour. If it is not a basic colour, a higher value number should be stored, but the interpreter should internally keep track of the real number so that it can be used elsewhere.

Viola does not correctly store the value of the basic colour in the window's colour data. This doesn't seem to affect the appearance of any games.

Viola is slow

Especially when running Inform 7 games, it seems.

All text is buffered

Under various circumstances, text output is not supposed to be buffered, but instead printed immediately to the screen. Viola buffers all text output.

With the speed of modern computers, this is barely, if at all, noticeable.

Add command line history

Beyond Zork 57.871221 upper window text not displayed properly

Where there should be newlines, there are none. The text just prints at the bottom of the description box, in one long line, running off the end of the screen.

If game is unavailable, interpreter hangs

Freefall.z5 does not work

The blocks do not fall, which indicates that timed input is not actually working correctly. Very likely to affect other games.

Pay attention to @buffer_screen

@buffer_screen allows the game to hint that the interpreter should use a backing store for all screen updates, until the game is finished whatever complicated drawing it's doing. It is legal to ignore the opcode completely, but it might be worthwhile using.

Slight text positioning problem.

In Zork Zero, as soon as the game starts, the location 'Flatheadia' in the status window at the top of the screen slightly overlays the curve on the banner image the text is printed on. Below that, the 'Score' text should have a ':', but this is missing. Probably the same issue.

Quetzal save files are wrong

When trying to restore the file, Frotz crashes with a 'Umem chunk wrong size' error.

Option to set Tandy bit

z6 menus not recognized

Version 6 of the Z-Machine allows the game to add menus to the interpreter's menu bar. This is an optional feature, which Viola does not support primarily because Viola does not currently have a menu bar.

Fixed-width header bit doesn't work

Illegal characters can be input

The interpreter should only allow input for characters the game defines for input. Currently it allows undefined characters to be passed to the game.

z6 tab character

The z6 tab character is supposed to behave differently depending on whether it is printed at the beginning of a line, or in the middle of one. Viola does not do this, instead printing 3 spaces at all times.

curses.z5 16.951024 closes interpreter after title screen

Restore crashes Viola

Coordinates are wrong

The Z-Machine screen and window positions start from 1,1. Currently, Viola assumes they start from 0,0, because that's how pygame works. Some simple conversion of coordinates is needed.

Pixel colour picking returning incorrect colour

In Zork Zero, in the banner at the top, the background colour for some of the text is a lighter shade than the banner it's printed on.

Leaving this alone for now, because it helps highlight the text positioning bug, and might help fix it.

z6 redraw flag

When the interpreter thinks it has messed up the game display, and wants the game to redraw it, it can set a flag in the header. The main time to do this would be when the interpreter window is resized. Viola does not do this at all.

Font 3 support

Input text not correctly redisplayed after timer interrupt routine

From the Standard: The routine is permitted to print to the screen even if it returns false to signal "carry on": the interpreter should notice and redraw the input line so far, before input continues.

Viola does not do this.

User font selection

Strict Z-Machine feature availability

Some Z-Machine features are requested by games using flags in the header, and the interpreter is not expected to provide the feature if the game does not ask for it. An option to turn off any features not explicitly requested might prove mildly useful.