jsDosbox testing and bug reporting

[DOSGuy]

Chrome has finally dropped support for NPAPI plug-ins like Java, and Edge has never supported plug-ins. As more and more people are arriving on the site without Java, I've been planning to offer a JavaScript alternative for a long time, hoping that HTML5 would catch up to the capabilities of the technologies it's supposedly going to replace.

Until now, visitors without Java would see a message advising them to go to Oracle's website to download it. Visitors without Java will now be given a link to play the game in jsDosbox. This will not happen automatically; jDosbox is still the preferred option because it's faster and compatible with more games. For now, I am presenting a list of which browsers support Java and which ones don't, and encouraging visitors to use Java if they can.

I haven't had time to test 370 versions of 348 games that can currently be played in jDosbox, so the option to play in jsDosbox is presented for every game. I've created this thread to report bugs and compatibility issues with games under jsDosbox for the benefit of visitors, and so that we can provide bug reports to the author.

I've changed the default CPU to Pentium and set RAM to 16 MB so that games like MDK won't refuse to play based on system requirements, but any game that requires a Pentium is going to be too slow to be playable anyway.

There is no need to report that games play slowly or that sound is lousy. Those are current limitations of the emulator that will affect every game. Also, some games refuse to load when they are unable to create files, but the author expects to have this issue fixed in the next version. Instead, I'd like to see stuff like this:

MDK
Unplayable due to DOS/4GW divide by zero error.

Thanks for testing, everyone!

[DOSGuy]

Unplayable games:

MDK
Unplayable due to DOS/4GW divide by zero error.
"Uncaught TypeError: Cannot read property 'U' of null" on jsdosbox.nocache.js:4831

Games with issues:

1993 Holiday Lemmings
Large offset between user's cursor and in-game cursor, possibly due to 2x scaling.

[MrFlibble]

I'm on Firefox and I just tried to run Prince of Persia. It's slow to the point of being unplayable. The sound lags severely. Maybe for now just turn off the sound if jsDOSBox has issues with it? I think you can launch the game with a command line option that turns sound off. Also maybe if the machine is set to EGA it will perform better (at the cost of less fancy graphics)?

Commander Keen: Invasion of the Vorticons plays fine. BTW, the aspect ratio correction is off for all games as it seems. Will it impair performance even more if it is turned on?

[NY00123]

Hey there, it's great to see you finding the time to take care of this, despite possible difficulties!

I've also made a few tests with Firefox 43.0.4 for Linux.
- Don't think there's a lot of new to add about Keen 1 and POP. Keen 1 stopped outputting sounds at some point (although a silent noise could still be heard), but that's probably just a part of the usual sound problems.
- Keen 4 has a minor graphical glitch while scrolling (looking like a blinking line with older contents) that can be fixed by toggling on the SVGA Compatibility option in the menus. I know this is not required in vanilla DOSBox with machine=svga_s3, but may be with other machines. (It was required with machine=vgaonly before the last SVN revision.)
- Xargon (registered version) report: Not sure it falls under your category of "some games refuse to load when they are unable to create files", but this seems to freeze the browser, so I get asked (in a dialog box) if I want to let the JS script continue running. Even after confirming more than once, it's still not complete.

Now, I'm not sure if it's off-topic, but I'm wondering why have you preferred to use jsDosbox over another alternative, say EM-DOSBox. I'm aware of the following comment of yours from that other thread (viewtopic.php?p=7530#p7530):

jsDosbox has a fraction of the performance of jDosbox. I don't know about EM-DOSBox, other than that the sound was so awful that the Internet Archive disabled it to stop the complaints. If there was a JavaScript alternative to jDosbox I would use it, but nothing seems to be comparable yet.

At least for me, Keen 1 + 4, and the POP demo, as available from the Internet Archive, currently seem to work better for me, including also the sounds and music. I agree this may greatly depend on the environment (e.g., OS and browser) in use and the way the game applets are set-up, though.

BTW, the aspect ratio correction is off for all games as it seems. Will it impair performance even more if it is turned on?

At least in vanilla DOSBox, it is my understanding that there shouldn't be a great difference other than a bit more work for the GPU for the scaling, if used; Say, with output=opengl. Software scaling is done if output=surface is used, which has its own impact, even if not that great.

[DOSGuy]

Commander Keen: Invasion of the Vorticons plays fine. BTW, the aspect ratio correction is off for all games as it seems. Will it impair performance even more if it is turned on?

If you're talking about converting non-square pixel resolutions like 320x200 to 4:3 aspect ratio, that's turned off on jDosbox too. I remember a performance penalty under regular DOSBox. jsDosbox can't afford anything that's going to slow it down.

Xargon (registered version) report: Not sure it falls under your category of "some games refuse to load when they are unable to create files", but this seems to freeze the browser, so I get asked (in a dialog box) if I want to let the JS script continue running. Even after confirming more than once, it's still not complete.

Yes, Xargon is one of the games that I tested that failed due to an inability to write files.

Now, I'm not sure if it's off-topic, but I'm wondering why have you preferred to use jsDosbox over another alternative, say EM-DOSBox.

There are a couple of reasons. The first is that jsDosbox can be downloaded as a ZIP file and uploaded directly to a website. I did have to hack the minified JavaScript file because it was looking for a CSS file in the wrong location, and because I needed to control where the canvas would appear on the page. I also removed some CSS that turned the page blue. As far as I'm concerned, the JS file shouldn't be forcibly linking to CSS files, since the appearance of the page should be left to the webmaster. Anyway, it's pretty much ready to upload and only required a few hacks to get it working.

EM-DOSBox, on the other hand, downloads as source code that needs to be compiled. I'm a Windows user, I don't compile software. According to the GitHub page, "Compiling in Windows is not supported. The build process requires a Unix-like environment due to use of GNU Autotools." I have Ubuntu running in a VM so I may give this a try, but this is a much bigger hassle than jsDosbox is.

The other reason is because I'm talking to the author. When danoon first posted about jDosbox in this forum, it had a lot of issues for a lot of games on the site. The inability to write files was one of them, and terrible mouse support was another. danoon was a huge sport about hearing those concerns and fixing them quickly. He went way out of his way to make jDosbox what I wanted it to be.

Since neither one currently meets my needs, I'll need to work with the authors to make feature requests and request bug fixes. jsDosbox is hosted on SourceForge, so I had no trouble making contact with the author. He was already in the process of releasing v3.3 (which was released a few days ago), so I'm not sure if it was affected by my feedback or not, but it had something in it that I asked for: the ability to write files.

EM-DOSBox is hosted on GitHub, which appears to no longer have a private messaging feature, so I haven't been able to talk to the author yet. If EM-DOSBox can do things that jsDosbox can't, I'm willing to switch, but I would rather use a project that I have some ability to influence than one that I have no control over.