Guidance on writing new plugins

[mortenboye]

What is the recommended approach to writing new plugins for flutter-pi?
Looking at the gpiod plugin, it looks like a dart package (no native code) combined with a gpiod.c file in the plugins folder.
What are the steps necessary to link and build the .c file and make flutter-pi aware of new plugins?

[ardera]

Looking at the gpiod plugin, it looks like a dart package (no native code) combined with a gpiod.c file in the plugins folder.

Exactly, a flutter-pi plugin is just:

• a dart package for the dart-side implementation
• typically, a my_plugin.c file inside src/plugins and a my_plugin.h file inside include/plugins (if you need more files, just create a my_plugin folder inside src/plugins and include/plugins which contains your plugin source files)
• some code inside src/plugin_registry.c to make your plugin known to the plugin registry
• of course, you also need to update the Makefile so it compiles your src/plugins/my_plugin.c file

It's also "convention" to implement a flag, like BUILD_MY_PLUGIN, so people can choose when compiling flutter-pi whether your plugin should be built and included in the finished binary. (To be more precise, the BUILD_MY_PLUGIN flag should do nothing more than enable/disable the registration of your plugin to the plugin_registry, see here and here)

What are the steps necessary to link and build the .c file and make flutter-pi aware of new plugins?

So, in practice, you'll have to add 6 lines to pluginregistry.c to make your plugin known to flutter-pi:

// my_plugin.h should contain the definitions of `my_plugin_init`
// and `my_plugin_deinit`
#ifdef BUILD_MY_PLUGIN
#    include <plugins/my_plugin.h>
#endif

// . . .

struct flutterpi_plugin hardcoded_plugins[] = {

// . . . the other plugins' registrations here

#ifdef BUILD_MY_PLUGIN
    {.name = "my_plugin", .init = my_plugin_init, .deinit = my_plugin_deinit},
#endif
};

Then you need to update the Makefile so your plugin gets built:

1. Add src/plugins/my_plugin.c to the definition of the SOURCES variable
2. Add the -DBUILD_MY_PLUGIN c-flag to the definition of the REAL_CFLAGS variable

[mortenboye]

Perfect, works! Thanks, closing...