• Example Clap Plugins
  • Notes on GUI, static build vs dynamic build and symbols
• Building on various platforms
  • Headless
  • macOS with vcpkg
  • Windows
    • Enable long path support
    • Build
  • Linux, using vcpkg (static)

Example Clap Plugins

This repo serves as an example to demonstrate how to create a CLAP plugin.

Notes on GUI, static build vs dynamic build and symbols

The plugins use Qt for the GUI.

It is fine to dynamically link to Qt for a host, but it is very dangerous for a plugin.

Also one very important aspect of the plugin is the distribution. Ideally a clap plugin should be self contained: it should not rely upon symbols from the host, and it should export only one symbol: clap_entry.

You should be aware that even if you hide all your symbols some may still remain visible at unexpected places. Objective-C seems to register every classes including those coming from plugins in a flat namespace. Which means that if two plugins define two different Objective-C classes but with the same, they will clash which will result in undeflined behavior.

Qt uses a few Objective-C classes on macOS. So it is crucial to use QT_NAMESPACE.

We abstracted the relation between the plugin and the GUI: AbstractGui and AbstractGuiListener which lets us transparently insert proxies.

The GUI itself work with proxy objects to the parameters, transport info, ... They are then bound into QML objects. See Knob.qml and parameter-proxy.hh.

Building on various platforms

Headless

This build variant doesn't include the GUI and is much faster to build due to the lack of dependencies.

git clone --recurse-submodules https://github.com/free-audio/clap-plugins
cd clap-plugins
cmake --preset ninja-headless
cmake --build --preset ninja-headless

macOS with vcpkg

# Install build tools
brew install cmake ninja autoconf automake

# Checkout the code
git clone --recurse-submodules https://github.com/free-audio/clap-plugins
cd clap-plugins
scripts/build-gui.sh

Windows

Enable long path support

Make sure your system supports long paths. Run this in an administrator PowerShell:

New-ItemProperty -Path "HKLM:\SYSTEM\CurrentControlSet\Control\FileSystem" -Name "LongPathsEnabled" -Value 1 -PropertyType DWORD -Force

Reference: https://docs.microsoft.com/en-us/windows/win32/fileio/maximum-file-path-limitation?tabs=powershell

Build

Install Visual Studio 2022; you can install it from the Microsoft Store. It can also install git and CMake for you.

Use the following command inside Powershell:

# Checkout the code very close to the root to avoid windows long path issues...
cd c:\
git clone --recurse-submodules https://github.com/free-audio/clap-plugins c-p
cd c-p

Powershell.exe -noexit -executionpolicy bypass -File .\scripts\build-gui.ps1

Linux, using vcpkg (static)

# on unbuntu, adapt to your distribution and package manager
sudo apt install git ninja-build cmake

# on archlinux, adapt to your distribution and package manager
sudo pacman -S git ninja cmake

git clone --recurse-submodules https://github.com/free-audio/clap-plugins
cd clap-plugins
scripts/build-gui.sh