\S0{plugindlls} Plugin 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 plugins directory for DLLs and makes a list of the plugins 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 plugin 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. If the /NOUNLOAD option is specified the DLL will not be unloaded until the installer exits or the next time you use the DLL without /NOUNLOAD. Please note that the last call to the plugin must not have the /NOUNLOAD flag or the plugin will not be deleted from $PLUGINSDIR, thus garbage will be left on the user's machine.

\S1{usingplug} Using Plugin Commands

A plug-in call looks like this:

\c InstallOptions::dialog "ini_file_location.ini"

All parameters are pushed onto the stack (in this case, the plug-in function only needs one parameter). Some plugin 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.

\S1{disablingplug} Disabling Plugin Unloading

If you don't want to unload the DLL after calling a function, use /NOUNLOAD as the first parameter. For example:

\c dll:function /NOUNLOAD "param"

You can also use \R{setpluginunload}{SetPluginUnload} alwaysoff to avoid writing /NOUNLOAD each and every time you use the same plugin.

\S1{calldiskplug} Calling plug-ins manually

If you want to call a plug-in that is stored on user's hard drive or somewhere else, use \R{callinstdll}{CallInstDLL}. Almost all plug-ins provide installer functionality, so using plug-in commands is way easier. Using \R{callinstdll}{CallInstDLL} can be useful when you have created plug-ins that should be linked to a certain version of your application and are being copied to the installation folder.
