Implement the CLAP latency extension

src/plugin/bridges/clap-impls/plugin-proxy.cpp

@@ -21,6 +21,8 @@
 ClapHostExtensions::ClapHostExtensions(const clap_host& host) noexcept
     : audio_ports(static_cast<const clap_host_audio_ports_t*>(
           host.get_extension(&host, CLAP_EXT_AUDIO_PORTS))),
+      latency(static_cast<const clap_host_latency_t*>(
+          host.get_extension(&host, CLAP_EXT_LATENCY))),
       note_ports(static_cast<const clap_host_note_ports_t*>(
           host.get_extension(&host, CLAP_EXT_NOTE_PORTS))),
       params(static_cast<const clap_host_params_t*>(
@@ -34,6 +36,7 @@ clap::host::SupportedHostExtensions ClapHostExtensions::supported()
     const noexcept {
     return clap::host::SupportedHostExtensions{
         .supports_audio_ports = audio_ports != nullptr,
+        .supports_latency = latency != nullptr,
         .supports_note_ports = note_ports != nullptr,
         .supports_params = params != nullptr,
         .supports_tail = tail != nullptr};
@@ -65,6 +68,9 @@ clap_plugin_proxy::clap_plugin_proxy(ClapPluginBridge& bridge,
           .count = ext_audio_ports_count,
           .get = ext_audio_ports_get,
       }),
+      ext_latency_vtable(clap_plugin_latency_t{
+          .get = ext_latency_get,
+      }),
       ext_note_ports_vtable(clap_plugin_note_ports_t{
           .count = ext_note_ports_count,
           .get = ext_note_ports_get,
@@ -210,6 +216,9 @@ clap_plugin_proxy::plugin_get_extension(const struct clap_plugin* plugin,
     if (self->supported_extensions_.supports_audio_ports &&
         strcmp(id, CLAP_EXT_AUDIO_PORTS) == 0) {
         extension_ptr = &self->ext_audio_ports_vtable;
+    } else if (self->supported_extensions_.supports_latency &&
+               strcmp(id, CLAP_EXT_LATENCY) == 0) {
+        extension_ptr = &self->ext_latency_vtable;
     } else if (self->supported_extensions_.supports_note_ports &&
                strcmp(id, CLAP_EXT_NOTE_PORTS) == 0) {
         extension_ptr = &self->ext_note_ports_vtable;
@@ -274,6 +283,15 @@ clap_plugin_proxy::ext_audio_ports_get(const clap_plugin_t* plugin,
     }
 }
 
+uint32_t CLAP_ABI
+clap_plugin_proxy::ext_latency_get(const clap_plugin_t* plugin) {
+    assert(plugin && plugin->plugin_data);
+    auto self = static_cast<const clap_plugin_proxy*>(plugin->plugin_data);
+
+    return self->bridge_.send_main_thread_message(
+        clap::ext::latency::plugin::Get{.instance_id = self->instance_id()});
+}
+
 uint32_t CLAP_ABI
 clap_plugin_proxy::ext_note_ports_count(const clap_plugin_t* plugin,
                                         bool is_input) {

src/plugin/bridges/clap-impls/plugin-proxy.h

@@ -21,6 +21,7 @@
 #include <vector>
 
 #include <clap/ext/audio-ports.h>
+#include <clap/ext/latency.h>
 #include <clap/ext/note-ports.h>
 #include <clap/ext/params.h>
 #include <clap/ext/tail.h>
@@ -60,6 +61,7 @@ struct ClapHostExtensions {
     clap::host::SupportedHostExtensions supported() const noexcept;
 
     const clap_host_audio_ports_t* audio_ports = nullptr;
+    const clap_host_latency_t* latency = nullptr;
     const clap_host_note_ports_t* note_ports = nullptr;
     const clap_host_params_t* params = nullptr;
     const clap_host_tail_t* tail = nullptr;
@@ -137,6 +139,8 @@ class clap_plugin_proxy {
                                              bool is_input,
                                              clap_audio_port_info_t* info);
 
+    static uint32_t CLAP_ABI ext_latency_get(const clap_plugin_t* plugin);
+
     static uint32_t CLAP_ABI ext_note_ports_count(const clap_plugin_t* plugin,
                                                   bool is_input);
     static bool CLAP_ABI ext_note_ports_get(const clap_plugin_t* plugin,
@@ -240,6 +244,7 @@ class clap_plugin_proxy {
     // depends on whether the plugin supported this extension when we called
     // `clap_plugin::init()`.
     const clap_plugin_audio_ports_t ext_audio_ports_vtable;
+    const clap_plugin_latency_t ext_latency_vtable;
     const clap_plugin_note_ports_t ext_note_ports_vtable;
     const clap_plugin_params_t ext_params_vtable;
     const clap_plugin_tail_t ext_tail_vtable;

src/plugin/bridges/clap.cpp

@@ -115,6 +115,22 @@ ClapPluginBridge::ClapPluginBridge(const ghc::filesystem::path& plugin_path)
 
                     return Ack{};
                 },
+                [&](const clap::ext::latency::host::Changed& request)
+                    -> clap::ext::latency::host::Changed::Response {
+                    const auto& [plugin_proxy, _] =
+                        get_proxy(request.owner_instance_id);
+
+                    plugin_proxy
+                        .run_on_main_thread(
+                            [&, host = plugin_proxy.host_,
+                             latency =
+                                 plugin_proxy.host_extensions_.latency]() {
+                                latency->changed(host);
+                            })
+                        .wait();
+
+                    return Ack{};
+                },
                 [&](const clap::ext::note_ports::host::SupportedDialects&
                         request)
                     -> clap::ext::note_ports::host::SupportedDialects::