Import Functions

To use functions from another plugin in your C++ plugin, you need to generate language-specific header files. These headers provide the necessary wrappers to call functions exported by other plugins. This guide explains how to generate these headers and how to use them in your C++ plugin.

Generating Header Files

Plugify provides a unified generator tool to automatically generate header files for importing functions from other plugins. These headers include wrapper functions that handle the function calls and parameter passing.

Steps to Generate Bindings

plugify-gen -manifest ./plugins/plugin_from_another_language/plugin_from_another_language.pplugin -output ./output/ -lang cpp

Project Integration

After generating the module, integrate it into your C++ project:

cp -r ./output/external/plugify/include/plugin_from_another_language ./my_plugin/external/plugify/include/

target_include_directories(${PROJECT_NAME} PRIVATE
    ${CMAKE_CURRENT_SOURCE_DIR}/external/plugify/include
)
target_sources(${PROJECT_NAME} PRIVATE
    ${CMAKE_CURRENT_SOURCE_DIR}/external/plugify/include/plugin_from_another_language/plugin_from_another_language.cpp
)

#include <plugin_from_another_language/plugin_from_another_language.hpp>

Using Generated Wrapper Functions

The generated module contains wrapper functions that allow you to call functions from the other plugin. These wrappers handle the function address lookup and parameter passing.

Example Generated Header

Here’s an example of a generated header file for a plugin named plugin_from_another_language:

#pragma once

#include "enums.hpp"
#include "aliases.hpp"
#include "delegates.hpp"
#include <plugin_export.h>

// Generated from plugin_from_another_language.pplugin (group: core)

namespace plugin_from_another_language {

  using _ParamCallback = void (*)(int32_t, float, double, const plg::vec4&, const plg::vector<int64_t>&, char, const plg::string&, char16_t, int16_t);
}
extern "C" PLUGIN_API plugin_from_another_language::_ParamCallback __plugin_from_another_language_ParamCallback;
namespace plugin_from_another_language {
  inline void ParamCallback(int32_t a, float b, double c, const plg::vec4& d, const plg::vector<int64_t>& e, char f, const plg::string& g, char16_t h, int16_t k) {
    return __plugin_from_another_language_ParamCallback(a, b, c, d, e, f, g, h, k);
  }
} // namespace plugin_from_another_language

How It Works

• plugin_from_another_language.cpp defines the pointer __plugin_from_another_language_ParamCallback, initially nullptr.
• When your plugin loads, the C++ language module finds this exported pointer in your library and writes the address of the exported function into it.
• The wrapper function (ParamCallback) calls through the pointer, passing the parameters directly.
• If your build uses a version script with local: *;, add __plugin_from_another_language_*; under global:. Otherwise the module cannot see the pointer, it stays nullptr, and the first call crashes.

Example: Using the Generated Header

Here’s how you can use the generated header in your C++ plugin:

#include <plugin_from_another_language/plugin_from_another_language.hpp> // Include the generated header

void MyPluginFunction() {
    // Call the exported function from the other plugin
    plugin_from_another_language::ParamCallback(
        42,                // int32_t a
        3.14f,             // float b
        2.718,             // double c
        {1.0f, 2.0f, 3.0f, 4.0f}, // plg::vec4 d
        {100, 200},        // plg::vector<int64_t> e
        'x',               // char f
        "Hello, Plugify!", // plg::string g
        u'✓',              // char16_t h
        10                 // int16_t k
    );
}

When is Header Generation Necessary?

In C++, you need generated headers for every plugin you import, whatever language that plugin is written in. Without them, the compiler cannot reference the exported functions. Plugins written in dynamically-typed languages like Python do not need this step, because method binding happens at runtime.

Best Practices

1. Use the Generator Tool: Always use the Plugify generator tool (online or command-line) to generate headers for imported functions.
2. Include Generated Headers: Include the generated headers in your plugin source files to access the exported functions.
3. Test Thoroughly: Test the imported functions to ensure they work as expected.
4. Document Dependencies: Clearly document the plugins and functions your plugin depends on.

Conclusion

Importing functions from another plugin in C++ is straightforward when you use the Plugify generator tool to generate the necessary headers. These headers provide wrapper functions that handle function address lookup and parameter passing, making it easy to integrate functionality from other plugins. By following the steps and best practices outlined in this guide, you can create robust and interoperable plugins in the Plugify ecosystem.