Some fresh news: widescreen mode IS possible with Kingpin and it works perfectly!!
I wrote a first version of this post yesterday, while I was still attempting to fix some problems I had encountered. Now I have solved them all, so I am editing everything here to give you the final results of my experiments. It works!
This widescreen solution is based on an available hack for Daikatana, which also uses a Quake II-based engine. You can find the complete explanation here: http://rome.ro/smf/index.php?topic=6582.0;wap2
Thanks to Fresch, we now have a widescreen fix for Q2 engine that also applies to Kingpin.
Basically, this hack uses the highest resolution available, 1600*1200, and changes hexadecimal values to match those of a custom widescreen resolution. To do this, you must use an hexadecimal editor and open kingpin.exe file. Some excellent freewares are available on the net to do the trick - search Google.
I have tried a resolution of 1440*900 successfully, on Windows 7 x64 professional. In addition to the explanations on the link provided, here are special steps you MUST do in order not to crash the game or to end with unexpected results:
- copy both kingpin.exe and config.cfg on your desktop (config.cfg is in \*directory*\main\; with Vista and 7, this file is moved to Virtual Store by UAC if the application is not run as administrator - check Compatibility Files while browsing your Kingpin directory to find it). Make a backup of original files!
- apply the Daikatana widescreen hack in kingpin.exe as explained in the link
- open config.cfg and be sure to have the following values set correctly:
"set gl_mode 6" // this is the 1600*1200 in-game setting, which has been changed to custom widescreen resolution
"set fov 90" // I mistakenly asserted that setting fov to 100 would work perfectly; in fact this doesn't apply with Kingpin. Not only guns are not drawn anymore with this setting, but it also streches what is displayed. Usually, a 4:3 fov 90 corresponds to a 16:10 fov 100, but it is not the case here. I have compared many screenshots taken at the same spots ingame, and I can confirm that you must still use fov 90. Image is not stretched, but you lose some vertical portions ("Vert-" scaling: top and bottom of the display are cut off).
"set vid_fullscreen 1" // runs game in fullscreen mode, otherwise game would load in a window even with a correct resolution setting and you would have to setup everything manually each time you run the game again
"set viewsize 100" // a VERY important setting !! This is the "screen size" ingame option, which would be set to 110 if cursor is set to the far right. But by doing so, game struggles to launch fullscreen and crashes back to Windows desktop. So keep this value on 100, the slider will not be on the extreme right but it is normal.
Once you are done with config.cfg, open its properties and set it to "read only" to prevent kingpin.exe erasing your values. Paste both files into the original game folder (on Vista or 7, kingpin.exe in game folder and config.cfg in the Virtual Store, where you initially found it).
If you apply those tips, you should not encounter any problem: Kingpin game runs nicely, guns are drawn, and image is not stretched. Only con is, top and bottom of the display are cut, but it is not much of a problem as HUD elements are not hidden in the process.
I hope this widescreen fix will also work for you GOG.com customers! Please give a try and post some feedback here. Don't forget to backup your original files before any attempts.