Implement the CLAP latency extension

src/wine-host/bridges/clap-impls/host-proxy.cpp

@@ -48,6 +48,9 @@ clap_host_proxy::clap_host_proxy(ClapBridge& bridge,
           .is_rescan_flag_supported = ext_audio_ports_is_rescan_flag_supported,
           .rescan = ext_audio_ports_rescan,
       }),
+      ext_latency_vtable(clap_host_latency_t{
+          .changed = ext_latency_changed,
+      }),
       ext_note_ports_vtable(clap_host_note_ports_t{
           .supported_dialects = ext_note_ports_supported_dialects,
           .rescan = ext_note_ports_rescan,
@@ -71,6 +74,9 @@ clap_host_proxy::host_get_extension(const struct clap_host* host,
     if (self->supported_extensions_.supports_audio_ports &&
         strcmp(extension_id, CLAP_EXT_AUDIO_PORTS) == 0) {
         extension_ptr = &self->ext_audio_ports_vtable;
+    } else if (self->supported_extensions_.supports_latency &&
+               strcmp(extension_id, CLAP_EXT_LATENCY) == 0) {
+        extension_ptr = &self->ext_latency_vtable;
     } else if (self->supported_extensions_.supports_note_ports &&
                strcmp(extension_id, CLAP_EXT_NOTE_PORTS) == 0) {
         extension_ptr = &self->ext_note_ports_vtable;
@@ -157,6 +163,14 @@ void CLAP_ABI clap_host_proxy::ext_audio_ports_rescan(const clap_host_t* host,
         .owner_instance_id = self->owner_instance_id(), .flags = flags});
 }
 
+void CLAP_ABI clap_host_proxy::ext_latency_changed(const clap_host_t* host) {
+    assert(host && host->host_data);
+    auto self = static_cast<const clap_host_proxy*>(host->host_data);
+
+    self->bridge_.send_main_thread_message(clap::ext::latency::host::Changed{
+        .owner_instance_id = self->owner_instance_id()});
+}
+
 uint32_t CLAP_ABI
 clap_host_proxy::ext_note_ports_supported_dialects(const clap_host_t* host) {
     assert(host && host->host_data);

src/wine-host/bridges/clap-impls/host-proxy.h

@@ -19,6 +19,7 @@
 #include <atomic>
 
 #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>
@@ -72,6 +73,8 @@ class clap_host_proxy {
     static void CLAP_ABI ext_audio_ports_rescan(const clap_host_t* host,
                                                 uint32_t flags);
 
+    static void CLAP_ABI ext_latency_changed(const clap_host_t* host);
+
     static uint32_t CLAP_ABI
     ext_note_ports_supported_dialects(const clap_host_t* host);
     static void CLAP_ABI ext_note_ports_rescan(const clap_host_t* host,
@@ -109,6 +112,7 @@ class clap_host_proxy {
     // depends on whether the plugin supported this extension when the host
     // called `clap_plugin::init()`.
     const clap_host_audio_ports_t ext_audio_ports_vtable;
+    const clap_host_latency_t ext_latency_vtable;
     const clap_host_note_ports_t ext_note_ports_vtable;
     const clap_host_params_t ext_params_vtable;
     const clap_host_tail_t ext_tail_vtable;

src/wine-host/bridges/clap.cpp

@@ -29,6 +29,8 @@ namespace fs = ghc::filesystem;
 ClapPluginExtensions::ClapPluginExtensions(const clap_plugin& plugin) noexcept
     : audio_ports(static_cast<const clap_plugin_audio_ports_t*>(
           plugin.get_extension(&plugin, CLAP_EXT_AUDIO_PORTS))),
+      latency(static_cast<const clap_plugin_latency_t*>(
+          plugin.get_extension(&plugin, CLAP_EXT_LATENCY))),
       note_ports(static_cast<const clap_plugin_note_ports_t*>(
           plugin.get_extension(&plugin, CLAP_EXT_NOTE_PORTS))),
       params(static_cast<const clap_plugin_params_t*>(
@@ -42,6 +44,7 @@ clap::plugin::SupportedPluginExtensions ClapPluginExtensions::supported()
     const noexcept {
     return clap::plugin::SupportedPluginExtensions{
         .supports_audio_ports = audio_ports != nullptr,
+        .supports_latency = latency != nullptr,
         .supports_note_ports = note_ports != nullptr,
         .supports_params = params != nullptr,
         .supports_tail = tail != nullptr};
@@ -342,6 +345,14 @@ void ClapBridge::run() {
                         .result = std::nullopt};
                 }
             },
+            [&](clap::ext::latency::plugin::Get& request)
+                -> clap::ext::latency::plugin::Get::Response {
+                const auto& [instance, _] = get_instance(request.instance_id);
+
+                // We'll ignore the main thread requirement for simple lookups
+                // to avoid the synchronisation costs in hot code paths
+                return instance.extensions.latency->get(instance.plugin.get());
+            },
             [&](const clap::ext::note_ports::plugin::Count& request)
                 -> clap::ext::note_ports::plugin::Count::Response {
                 const auto& [instance, _] = get_instance(request.instance_id);

src/wine-host/bridges/clap.h

@@ -67,6 +67,7 @@ struct ClapPluginExtensions {
     clap::plugin::SupportedPluginExtensions supported() const noexcept;
 
     const clap_plugin_audio_ports_t* audio_ports = nullptr;
+    const clap_plugin_latency_t* latency = nullptr;
     const clap_plugin_note_ports_t* note_ports = nullptr;
     const clap_plugin_params_t* params = nullptr;
     const clap_plugin_tail_t* tail = nullptr;