Interact with CLAP bridge in libyabridge-clap.so

src/plugin/clap-plugin.cpp

@@ -18,6 +18,28 @@
 
 #include <clap/entry.h>
 
+#include "bridges/clap.h"
+
+using namespace std::literals::string_literals;
+
+namespace fs = ghc::filesystem;
+
+// These plugin libraries can be used in one of two ways: they can either be
+// loaded directly (the yabridge <4.0 way), or they can be loaded indirectly
+// from `yabridge-chainloader-*.so` (the yabridge >=4.0 way). The advantage of
+// chainloading this library from a tiny stub library is that yabridge can be
+// updated without having to also replace all of the library copies and that it
+// takes up less space on filesystems that don't support reflinking, but the
+// catch is that we no longer have one unique plugin bridge library per plugin.
+// This means that we cannot store the current bridge instance as a global in
+// this library (because it would then be shared by multiple chainloaders), and
+// that we cannot use `dladdr()` within this library to get the path to the
+// current plugin, because thatq would return the path to this shared plugin
+// library instead. To accommodate for this, we'll provide the usual plugin
+// entry points, and we'll also provide simple methods for initializing the
+// bridge so that the chainloading library can hold on to the bridge instance
+// instead of this library.
+
 /**
  * The number of active instances. Incremented when `clap_entry_init()` is
  * called, decremented when `clap_entry_exit()` is called. We'll initialize the
@@ -25,12 +47,49 @@
  * when a `clap_entry_exit()` call causes this to return back to 0.
  */
 std::atomic_size_t active_instances = 0;
+/**
+ * The global plugin bridge instance. Only used if this plugin library is used
+ * directly. When the library is chainloaded, this will remain a null pointer.
+ */
+std::unique_ptr<ClapPluginBridge> bridge;
 
-bool clap_entry_init(const char* plugin_path) {
+void log_init_error(const std::exception& error, const fs::path& plugin_path) {
+    Logger logger = Logger::create_exception_logger();
+
+    logger.log("");
+    logger.log("Error during initialization:");
+    logger.log(error.what());
+    logger.log("");
+
+    // Also show a desktop notification since most people likely won't see the
+    // above message
+    send_notification(
+        "Failed to initialize CLAP plugin",
+        error.what() +
+            "\nCheck the plugin's output in a terminal for more information"s,
+        plugin_path);
+}
+
+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
+        assert(!bridge);
+
+        // XXX: The host also provides us with the plugin path which we could
+        //      just use instead. Should we? The advantage of doing it this way
+        //      instead is that we'll have consistent behavior between all
+        //      plugin formats.
+        const fs::path plugin_path = get_this_file_location();
+        try {
+            bridge = std::make_unique<ClapPluginBridge>(plugin_path);
+
+            return true;
+        } catch (const std::exception& error) {
+            log_init_error(error, plugin_path);
+
+            return false;
+        }
     }
 
     return true;
@@ -40,18 +99,71 @@ 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
+        assert(bridge);
+
+        bridge.reset();
     }
 }
 
 const void* clap_entry_get_factory(const char* factory_id) {
-    // TODO: Do the thing
+    assert(bridge);
-    // TODO: Assertion
+    assert(factory_id);
+
+    return bridge->get_factory(factory_id);
 }
 
+// This visibility attribute doesn't do anything on data with external linkage,
+// but we'll include it here just because it's in the CLAP template
+#pragma GCC diagnostic push
+#pragma GCC diagnostic ignored "-Wattributes"
+
 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,
 };
+
+#pragma GCC diagnostic pop
+
+/**
+ * This function can be called from the chainloader to initialize a new plugin
+ * bridge instance. The caller should store the pointer and later free it again
+ * using the `yabridge_module_free()` function. If the bridge could not
+ * initialize due to an error, then the error will be logged and a null pointer
+ * will be returned.
+ */
+extern "C" YABRIDGE_EXPORT ClapPluginBridge* yabridge_module_init(
+    const char* plugin_path) {
+    assert(plugin_path);
+
+    try {
+        return new ClapPluginBridge(plugin_path);
+    } catch (const std::exception& error) {
+        log_init_error(error, plugin_path);
+
+        return nullptr;
+    }
+}
+
+/**
+ * Free a bridge instance returned by `yabridge_module_init`.
+ */
+extern "C" YABRIDGE_EXPORT void yabridge_module_free(
+    ClapPluginBridge* instance) {
+    if (instance) {
+        delete instance;
+    }
+}
+
+/**
+ * Create and return a factory from a bridge instance. Used by the chainloaders.
+ */
+extern "C" YABRIDGE_EXPORT const void* yabridge_module_get_factory(
+    ClapPluginBridge* instance,
+    const char* factory_id) {
+    assert(instance);
+    assert(factory_id);
+
+    return instance->get_factory(factory_id);
+}

src/plugin/meson.build

@@ -68,6 +68,20 @@ vst2_plugin_sources = files(
 
 if with_clap
   clap_plugin_sources = files(
+    '../common/communication/common.cpp',
+    '../common/configuration.cpp',
+    '../common/logging/clap.cpp',
+    '../common/logging/common.cpp',
+    '../common/audio-shm.cpp',
+    '../common/linking.cpp',
+    '../common/notifications.cpp',
+    '../common/plugins.cpp',
+    '../common/process.cpp',
+    '../common/utils.cpp',
+    '../include/llvm/small-vector.cpp',
+    'bridges/clap.cpp',
+    'host-process.cpp',
+    'utils.cpp',
     'clap-plugin.cpp',
   )
 endif