kgames

Thu, 31 Dec 2020 19:57:19 -0800
tags/fdo

Reviving Very Old X Code

I've taken the week between Christmas and New Year's off this year. I didn't really have anything serious planned, just taking a break from the usual routine. As often happens, I got sucked into doing a project when I received this simple bug report Debian Bug #974011

I have been researching old terminal and X games recently, and realized
that much of the code from 'xmille' originated from the terminal game
'mille', which is part of bsdgames.

...

[The copyright and license information] has been stripped out of all
code in the xmille distribution.  Also, none of the included materials
give credit to the original author, Ken Arnold.

The reason the 'xmille' source is missing copyright and license information from the 'mille' files is that they were copied in before that information was added upstream. Xmille forked from Mille around 1987 or so. I wrote the UI parts for the system I had at the time, which was running X10R4. A very basic port to X11 was done at some point, and that's what Debian has in the archive today.

At some point in the 90s, I ported Xmille to the Athena widget set, including several custom widgets in an Xaw extension library, Xkw. It's a lot better than the version in Debian, including displaying the cards correctly (the Debian version has some pretty bad color issues).

Here's what the current Debian version looks like:

Fixing The Bug

To fix the missing copyright and license information, I imported the mille source code into the "latest" Xaw-based version. The updated mille code had a number of bug fixes and improvements, along with the copyright information.

That should have been sufficient to resolve the issue and I could have constructed a suitable source package from whatever bits were needed and and uploaded that as a replacement 'xmille' package.

However, at some later point, I had actually merged xmille into a larger package, 'kgames', which also included a number of other games, including Reversi, Dominoes, Cribbage and ten Solitaire/Patience variants. (as an aside, those last ten games formed the basis for my Patience Palm Pilot application, which seems to have inspired an Android App of the same name...)

So began my yak shaving holiday.

Building Kgames in 2020

Ok, so getting this old source code running should be easy, right? It's just a bunch of C code designed in the 80s and 90s to work on VAXen and their kin. How hard could it be?

1. Everything was a 32-bit computer back then; pointers and ints were both 32 bits, so you could cast them with wild abandon and cause no problems. Today, testing revealed segfaults in some corners of the code.

2. It's K&R C code. Remember that the first version of ANSI-C didn't come out until 1989, and it was years later that we could reliably expect to find an ANSI compiler with a random Unix box.

3. It's X11 code. Fortunately (?), X11 hasn't changed since these applications were written, so at least that part still works just fine. Imagine trying to build Windows or Mac OS code from the early 90's on a modern OS...

I decided to dig in and add prototypes everywhere; that found a lot of pointer/int casting issues, as well as several lurking bugs where the code was just plain broken.

After a day or so, I had things building and running and was no longer hitting crashes.

Kgames 1.0 uploaded to Debian New Queue

With that done, I decided I could at least upload the working bits to the Debian archive and close the bug reported above. kgames 1.0-2 may eventually get into unstable, presumably once the Debian FTP team realizes just how important fixing this bug is. Or something.

Here's what xmille looks like in this version:

And here's my favorite solitaire variant too:

But They Look So Old

Yeah, Xaw applications have a rustic appearance which may appeal to some, but for people with higher resolution monitors and “well seasoned” eyesight, squinting at the tiny images and text makes it difficult to enjoy these games today.

How hard could it be to update them to use larger cards and scalable fonts?

Xkw version 2.0

I decided to dig in and start hacking the code, starting by adding new widgets to the Xkw library that used cairo for drawing instead of core X calls. Fortunately, the needs of the games were pretty limited, so I only needed to implement a handful of widgets:

KLabel. Shows a text string. It allows the string to be left, center or right justified. And that's about it.

KCommand. A push button, which uses KLabel for the underlying presentation.

KToggle. A push-on/push-off button, which uses KCommand for most of the implementation. Also supports 'radio groups' where pushing one on makes the others in the group turn off.

KMenuButton. A button for bringing up a menu widget; this is some pretty simple behavior built on top of KCommand.

KSimpleMenu, KSmeBSB, KSmeLine. These three create pop-up menus; KSimpleMenu creates a container which can hold any number of KSmeBSB (string) and KSmeLine (separator lines) objects).

KTextLine. A single line text entry widget.

The other Xkw widgets all got their rendering switched to using cairo, plus using double buffering to make updates look better.

SVG Playing Cards

Looking on wikimedia, I found a page referencing a large number of playing cards in SVG form That led me to Adrian Kennard's playing card web site that let me customize and download a deck of cards, licensed using the CC0 Public Domain license.

With these cards, I set about rewriting the Xkw playing card widget, stripping out three different versions of bitmap playing cards and replacing them with just these new SVG versions.

SVG Xmille Cards

Ok, so getting regular playing cards was good, but the original goal was to update Xmille, and that has cards hand drawn by me. I could just use those images, import them into cairo and let it scale them to suit on the screen. I decided to experiment with inkscape's bitmap tracing code to see what it could do with them.

First, I had to get them into a format that inkscape could parse. That turned out to be a bit tricky; the original format is as a set of X bitmap layers; each layer painting a single color. I ended up hacking the Xmille source code to generate the images using X, then fetching them with XGetImage and walking them to construct XPM format files which could then be fed into the portable bitmap tools to create PNG files that inkscape could handle.

The resulting images have a certain charm:

I did replace the text in the images to make it readable, otherwise these are untouched from what inkscape generated.

The Results

Remember that all of these are applications built using the venerable X toolkit; there are still some non-antialiased graphics visible as the shaped buttons use the X Shape extension. But, all rendering is now done with cairo, so it's all anti-aliased and all scalable.

Here's what Xmille looks like after the upgrades:

And here's spider:

Once kgames 1.0 reaches Debian unstable, I'll upload these new versions.