The new way is very inefficient in terms of installer size and install time: Compressing with zllib and then with lzma2 may result in a larger overall size than only compressing with lzma2, e.g. “Snapshot“ which becomes about 1 % larger that way.
I think you have to use the check_if_install for some installers that have alternative chunks for the same file that get chose according to the target Windows version (and architecture).

played around with the innoextract source code and managed to hack in some basic support for the new installers

https://github.com/immi101/innoextract/tree/gogextract

just grab the source, and use the same procedure as for the original to compile then pass the --gog flag to tell it to decompress the galaxy data, e.g. the installers support conditional installs depending on game language, os type(32/64 bit) and windows version, so there are three more command line parameters to set these.
with no parameter given it defaults to: --lang en-US --winver win7 --osbits 64
caveat: I haven't found an updated installer in my library that actually makes use of this, so this may not work at all :p

TODO:
- handle dependencies like scriptinterpreter.exe (if we even need that ?!?)
- test more than one installer ;)

side note: eador genesis just crashes with wine 3.0 for me :( pretty sure that this game used to work at some point, hm

as far as I can tell the galaxy data is only compressed with zlib. it's not compressed twice. While that may result in a bigger file size (compared to LZMA2) depending on the game I doubt it would be slower. if anything zlib should be faster than lzma I think.

Good work!

Same for me. Out of 4 new installer I have tested (arcanum, capitalism 2, eador and outcast) only one works out of the box (in wine) - outcast.

I did a quick test with Arcanum, and it doesn’t work even if you run the installer through WINE instead of using one of your new extraction methods. Actually, I would be quite curious to know if it does run on Windows in its current state.

To me it looks like this new packaging scheme broke a couple things more than just the extraction with innoextract.

Brilliant stuff. Getting this into upstream innoextract has to be the way forward, I'm sure. Thanks for working on this.

I just did a quick test - downloaded the installer (from the site, not through Galaxy), installed it and played it on Windows 7. It installs and runs just fine, except for graphic corruption in the main view (which is probably due to running this on a business laptop with no drivers or directx or anything gaming related installed).

I've just tried it on Windows 7, too. I have a decent gaming laptop, and this is what I get:

In the old installer exe was different, my guess it was patched with unofficial patch + GOG made some additional changes. Anyway, after applying unofficial patch, game works fine in wine.

....Huh. That's exactly what I had, too.

-edit- if I can find the time, I'll try it out when I'm at home later today, on my Win10 PC.

the Arcanum.exe from the new installer is packed with UPX.
install upx, decompress the exe with (upx -d Arcanum.exe), and you have the same old exe as in the previous installer (size ~2 mb). and now it does work in wine.

the fact that the packed exe does not work is most likely something that needs to be fixed in wine.

Thanks for the info.

Confirmed.
The decompressed exe run fine.

Filesize:
2011136 Arcanum.exe (decompressed 1.0.7.4_(19476))
2007040 Arcanum.exe (2.0.0.15 (gog-15))

MD5sum:
436a29f6d6adcb30ba47f492e4f1dcbb Arcanum.exe (decompressed 1.0.7.4_(19476))
17dafde24628890fa13e3b8d356e0bf1 Arcanum.exe (2.0.0.15 (gog-15))

yeah, my bad. I didn't actually compare the hashes of the two exes since I don't have the old installer at hand anymore.
I just went with the information posted in this thread and just assumed it was the same based on the similar size and the fact that it is working. probably should have phrased that better.

No problem, that’s in part because you said it was the same that I thought about double-checking ;)