Add a basic CLAP plugin factory implementation

Which can only list plugins without creating them.

src/common/serialization/clap/plugin.cpp

@@ -43,7 +43,7 @@ descriptor::descriptor(const clap_plugin_descriptor_t& original)
     }
 }
 
-clap_plugin_descriptor_t descriptor::get() const {
+const clap_plugin_descriptor_t* descriptor::get() const {
     // This should be the minimum of yabridge's supported CLAP version and
     // the plugin's supported CLAP version
     clap_version_t supported_clap_version = clap_version;
@@ -55,14 +55,15 @@ clap_plugin_descriptor_t descriptor::get() const {
         supported_clap_version = CLAP_VERSION;
     }
 
-    // `features_ptrs` needs to be populated as envp-style null terminated array
+    // `features_ptrs` needs to be populated as an envp-style null terminated
+    // array
     features_ptrs.resize(features.size() + 1);
     for (size_t i = 0; i < features.size(); i++) {
         features_ptrs[i] = features[i].c_str();
     }
     features_ptrs[features.size()] = nullptr;
 
-    return clap_plugin_descriptor_t{
+    clap_descriptor = clap_plugin_descriptor_t{
         .clap_version = supported_clap_version,
         .id = id.c_str(),
         .name = name.c_str(),
@@ -74,6 +75,8 @@ clap_plugin_descriptor_t descriptor::get() const {
         .description = description ? description->c_str() : nullptr,
         .features = features_ptrs.data(),
     };
+
+    return &clap_descriptor;
 }
 
 }  // namespace plugin

src/common/serialization/clap/plugin.h

@@ -68,7 +68,7 @@ struct descriptor {
      * to this object's fields, so this descriptor is only valid as long as this
      * object is alive and doesn't get moved.
      */
-    clap_plugin_descriptor_t get() const;
+    const clap_plugin_descriptor_t* get() const;
 
     template <typename S>
     void serialize(S& s) {
@@ -98,6 +98,10 @@ struct descriptor {
      * Populated as part of `get()`.
      */
     mutable std::vector<const char*> features_ptrs;
+    /**
+     * The CLAP descriptor populated and returned from `get()`.
+     */
+    mutable clap_plugin_descriptor_t clap_descriptor;
 };
 
 }  // namespace plugin

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

@@ -0,0 +1,61 @@
+// 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 "plugin-factory-proxy.h"
+
+#include "../clap.h"
+
+clap_plugin_factory_proxy::clap_plugin_factory_proxy(
+    ClapPluginBridge& bridge,
+    std::vector<clap::plugin::descriptor> descriptors)
+    : plugin_factory_vtable(clap_plugin_factory_t{
+          .get_plugin_count = plugin_factory_get_plugin_count,
+          .get_plugin_descriptor = plugin_factory_get_plugin_descriptor,
+          .create_plugin = plugin_factory_create_plugin,
+      }),
+      bridge_(bridge),
+      descriptors_(std::move(descriptors)){};
+
+uint32_t CLAP_ABI clap_plugin_factory_proxy::plugin_factory_get_plugin_count(
+    const struct clap_plugin_factory* factory) {
+    assert(factory);
+    auto self = reinterpret_cast<const clap_plugin_factory_proxy*>(factory);
+
+    return self->descriptors_.size();
+}
+
+const clap_plugin_descriptor_t* CLAP_ABI
+clap_plugin_factory_proxy::plugin_factory_get_plugin_descriptor(
+    const struct clap_plugin_factory* factory,
+    uint32_t index) {
+    assert(factory);
+    auto self = reinterpret_cast<const clap_plugin_factory_proxy*>(factory);
+
+    if (index < self->descriptors_.size()) {
+        return self->descriptors_[index].get();
+    } else {
+        return nullptr;
+    }
+}
+
+const clap_plugin_t* CLAP_ABI
+clap_plugin_factory_proxy::plugin_factory_create_plugin(
+    const struct clap_plugin_factory* factory,
+    const clap_host_t* host,
+    const char* plugin_id) {
+    // TODO: Implement
+    return nullptr;
+}

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

@@ -0,0 +1,69 @@
+// 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/>.
+
+#pragma once
+
+#include <vector>
+
+#include <clap/plugin-factory.h>
+
+#include "../../common/serialization/clap/plugin.h"
+
+// Forward declaration to avoid circular includes
+class ClapPluginBridge;
+
+/**
+ * A proxy for a plugin's `clap_plugin_factory`.
+ */
+class clap_plugin_factory_proxy {
+   public:
+    /**
+     * The vtable for `clap_plugin_factory`, requires that this object is never
+     * moved or copied. This is positioned at the start of the struct so we can
+     * cast between them (with only a bit of UB).
+     */
+    const clap_plugin_factory_t plugin_factory_vtable;
+
+    /**
+     * Construct the plugin factory proxy based on the plugin descriptors
+     * retrieved from a `clap::plugin_factory::ListReponse`.
+     */
+    clap_plugin_factory_proxy(
+        ClapPluginBridge& bridge,
+        std::vector<clap::plugin::descriptor> descriptors);
+
+    clap_plugin_factory_proxy(const clap_plugin_factory_proxy&) = delete;
+    clap_plugin_factory_proxy& operator=(const clap_plugin_factory_proxy&) =
+        delete;
+    clap_plugin_factory_proxy(clap_plugin_factory_proxy&&) = delete;
+    clap_plugin_factory_proxy& operator=(clap_plugin_factory_proxy&&) = delete;
+
+    static uint32_t CLAP_ABI
+    plugin_factory_get_plugin_count(const struct clap_plugin_factory* factory);
+    static const clap_plugin_descriptor_t* CLAP_ABI
+    plugin_factory_get_plugin_descriptor(
+        const struct clap_plugin_factory* factory,
+        uint32_t index);
+    static const clap_plugin_t* CLAP_ABI
+    plugin_factory_create_plugin(const struct clap_plugin_factory* factory,
+                                 const clap_host_t* host,
+                                 const char* plugin_id);
+
+   private:
+    ClapPluginBridge& bridge_;
+
+    std::vector<clap::plugin::descriptor> descriptors_;
+};

src/plugin/meson.build

@@ -80,6 +80,7 @@ if with_clap
     '../common/serialization/clap/plugin.cpp',
     '../common/utils.cpp',
     '../include/llvm/small-vector.cpp',
+    'bridges/clap-impls/plugin-factory-proxy.cpp',
     'bridges/clap.cpp',
     'host-process.cpp',
     'utils.cpp',