4.11 Plug-in DLLs
The abilities of the NSIS scripting language can be extended by utilising functionality provided in a DLL file. Probably the best known example of this is the InstallOptions.dll bundled with every NSIS release.
When the NSIS compiler starts it scans the plug-ins directory for DLLs and makes a list of the plug-ins found and their exported functions. During compilation, if a sequence such as fred::flintstone is encountered where the compiler expected to find a language keyword the compiler will look through this list. If a list entry specifies that fred.dll exports function flintstone NSIS will pack the fred.dll file into the created installer binary.
During execution of a plug-in command NSIS will unpack the necessary DLL to a temporary folder ($PLUGINSDIR), push all of the arguments specified (right-to-left order), and then execute the DLL function.
4.11.1 Using Plug-in Commands
A plug-in call looks like this:
All parameters are pushed onto the stack (in this case, the plug-in function only needs one parameter). Some plug-in commands may not need any parameters on the stack, others might require more of them. To use a plug-in command you will need to read the documentation for the plug-in so that you know what parameters its functions require.
4.11.2 Calling plug-ins manually
If you want to call a plug-in that is stored on user's hard drive or somewhere else, use CallInstDLL. Almost all plug-ins provide installer functionality, so using plug-in commands is way easier. Using CallInstDLL can be useful when you have created plug-ins that are linked to a certain version of your application and are being copied to the installation folder.