GPL Patch Information
The basic GPL program file is named "gpl.exe". When you first began using GPL, this was the file that ran on startup. However over the years, we've learned how to modify the program in order to enhance it. These enhancements are in the form of patches which are .xml formatted files containing small pieces of code that change the original gpl.exe. All the car mods from the first 1965 F1 mod to the new 1955 F1 mod use patches.
Some patches are mod unique such as the ones that come with each car mod release; however, other patches are general purpose and can be used with some or all mods. For example, my Head Movement patch is a general purpose patch that can be used with any mod.
A patching program is needed to apply the patch to the gpl.exe. For years, we have used Paul Thurston's marvelous GEM+ program, version 2.5.32. GEM+ helps you do many things, but its main purpose is to patch the gpl.exe. Specifically, GEM+ makes a copy of the donor gpl.exe, renames the copy to the mod's unique name such as "gplc67.exe", and applies the patches to the copy. The donor gpl.exe is never patched by GEM+ and remains pristine for future use.
As a side note, there are a few GPL enhancements such as Pribluda which use a different method of patching. This program provides its own patching mechanism and doesn't use GEM+. If you want all of your mod .exes to use Pribluda, then you should patch the donor gpl.exe with Pribluda before using GEM+ to create the mod .exes.
Patches may be placed in three different locations and their utility is different with each:
1. Mod Installation Directory/Mods/GEM+/Mod Physics Directory--the patch will always be used by this mod. Most mod patches use this method.
2. Mod Installation Directory/Mods/GEM+/Mod Physics/Options Directory--the patch will only be used by this mod if its checkbox is checked in the GEM+ dropdown list. Use this method if you want to test a patch on one mod.
3. C:/GPLSecrets/GEM+/Options Directory--the patch will be used by all mods if its checkbox is checked in the GEM+ dropdown list. Use this method if you want to test a patch on all mods.
Whenever you add or delete a patch, delete the mod .exe and let GEM+ rebuild it to ensure that the patch is applied or removed. This procedure isn't always necessary, but is the safest approach.