Add minimal boilerplate for a CLAP plugin

meson.build

@@ -22,6 +22,7 @@ project(
 is_64bit_system = build_machine.cpu_family() not in ['x86', 'arm']
 with_32bit_libraries = (not is_64bit_system) or get_option('build.cpp_args').contains('-m32')
 with_bitbridge = get_option('bitbridge')
+with_clap = get_option('clap')
 with_system_asio = get_option('system-asio')
 with_winedbg = get_option('winedbg')
 with_vst3 = get_option('vst3')
@@ -40,6 +41,7 @@ with_vst3 = get_option('vst3')
 # These variables are used to generate a `config.h` file. The library names will
 # be prefixed with `lib` and suffixed with `.so`, and the host names will be
 # suffixed with `.exe`.
+clap_plugin_name = 'yabridge-clap'
 vst2_plugin_name = 'yabridge-vst2'
 vst3_plugin_name = 'yabridge-vst3'
 host_name_64bit = 'yabridge-host'
@@ -101,6 +103,10 @@ if with_bitbridge
   compiler_options += '-DWITH_BITBRIDGE'
 endif
 
+if with_clap
+  compiler_options += '-DWITH_CLAP'
+endif
+
 # This provides an easy way to start the Wine VST host using winedbg since it
 # can be quite a pain to set up
 if with_winedbg
@@ -239,6 +245,10 @@ wine_shell32_dep = declare_dependency(link_args : '-lshell32')
 wine_threads_dep = declare_dependency(link_args : '-lpthread')
 wine_uuid_dep = declare_dependency(link_args : '-luuid')
 
+if with_clap
+  clap_dep = dependency('clap', version : '>=1.1.1')
+endif
+
 # We need to build the VST3 SDK dependencies in tree because Meson won't let us
 # build both native, 32-bit cross compiled and 64-bit cross compiled
 # dependencies from a (CMake) subproject
@@ -293,9 +303,32 @@ shared_library(
   override_options : ['b_lto=true'],
 )
 
+if with_clap
+  # This is the CLAP equivalent of `libyabridge-vst2.so`. The Wine host
+  # applications can handle VST2, VST3, and CLAP plugins.
+  shared_library(
+    clap_plugin_name,
+    clap_plugin_sources,
+    native : true,
+    include_directories : include_dir,
+    dependencies : clap_plugin_deps,
+    cpp_args : compiler_options,
+  )
+  # TODO: Chainloader
+  # shared_library(
+  #   'yabridge-chainloader-clap',
+  #   clap_chainloader_sources,
+  #   native : true,
+  #   dependencies : chainloader_deps,
+  #   cpp_args : compiler_options + chainloader_compiler_options,
+  #   # See above
+  #   override_options : ['b_lto=true'],
+  # )
+endif
+
 if with_vst3
   # This is the VST3 equivalent of `libyabridge-vst2.so`. The Wine host
-  # applications can handle both VST2 and VST3 plugins.
+  # applications can handle both VST2, VST3 and CLAP plugins.
   shared_library(
     vst3_plugin_name,
     vst3_plugin_sources,

meson_options.txt

@@ -5,6 +5,13 @@ option(
   description : 'Build a 32-bit host application for hosting 32-bit plugins. See the readme for full instructions on how to use this.'
 )
 
+option(
+  'clap',
+  type : 'boolean',
+  value : true,
+  description : 'Whether to build the CLAP version of yabridge.'
+)
+
 option(
   'system-asio',
   type : 'boolean',

src/plugin/clap-plugin.cpp

@@ -0,0 +1,57 @@
+// yabridge: a Wine plugin bridge
+// Copyright (C) 2020-2022 Robbert van der Helm
+//
+// This program is free software: you can redistribute it and/or modify
+// it under the terms of the GNU General Public License as published by
+// the Free Software Foundation, either version 3 of the License, or
+// (at your option) any later version.
+//
+// This program is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+// GNU General Public License for more details.
+//
+// You should have received a copy of the GNU General Public License
+// along with this program.  If not, see <https://www.gnu.org/licenses/>.
+
+#include <atomic>
+
+#include <clap/entry.h>
+
+/**
+ * The number of active instances. Incremented when `clap_entry_init()` is
+ * called, decremented when `clap_entry_exit()` is called. We'll initialize the
+ * bridge when this is first incremented from 0, and we'll free the bridge again
+ * when a `clap_entry_exit()` call causes this to return back to 0.
+ */
+std::atomic_size_t active_instances = 0;
+
+bool clap_entry_init(const char* plugin_path) {
+    // This function can be called multiple times, so we should make sure to
+    // only initialize the bridge on the first call
+    if (active_instances.fetch_add(1, std::memory_order_seq_cst) == 0) {
+        // TODO: Increase reference count, init factory if it was zero
+    }
+
+    return true;
+}
+
+void clap_entry_deinit() {
+    // We'll free the bridge when this exits brings the reference count back to
+    // zero
+    if (active_instances.fetch_sub(1, std::memory_order_seq_cst) == 1) {
+        // TODO: Destroy the bridge instance
+    }
+}
+
+const void* clap_entry_get_factory(const char* factory_id) {
+    // TODO: Do the thing
+    // TODO: Assertion
+}
+
+CLAP_EXPORT const clap_plugin_entry_t clap_entry = {
+    .clap_version = CLAP_VERSION_INIT,
+    .init = clap_entry_init,
+    .deinit = clap_entry_deinit,
+    .get_factory = clap_entry_get_factory,
+};

src/plugin/meson.build

@@ -14,6 +14,22 @@ vst2_plugin_deps = [
   tomlplusplus_dep,
 ]
 
+if with_clap
+  clap_plugin_deps = [
+    configuration_dep,
+
+    asio_dep,
+    bitsery_dep,
+    clap_dep,
+    dl_dep,
+    function2_dep,
+    ghc_filesystem_dep,
+    rt_dep,
+    threads_dep,
+    tomlplusplus_dep,
+  ]
+endif
+
 if with_vst3
   vst3_plugin_deps = [
     configuration_dep,
@@ -50,6 +66,12 @@ vst2_plugin_sources = files(
   'vst2-plugin.cpp',
 )
 
+if with_clap
+  clap_plugin_sources = files(
+    'clap-plugin.cpp',
+  )
+endif
+
 if with_vst3
   vst3_plugin_sources = files(
     '../common/communication/common.cpp',