Partially implement IHostApplication

For now only works for directly connected components.

README.md

@@ -16,9 +16,9 @@ This branch is still very far removed from being in a usable state. Below is an
 incomplete list of things that still have to be done before this can be used:
 
 - Interfaces left to implement:
-  - `IHostApplication::createComponent()`
+  - `IHostApplication::createComponent()` for indirectly connected objects
-  - `IConnectionPoint::notify()`, and support for indirectly connecting
+  - `IConnectionPoint::notify()`, and support for indirectly connecting objects
-    components through message passing proxies
+    through connction proxies
   - `IEditController2`
   - All other mandatory interfaces
   - All other optional interfaces

src/wine-host/bridges/vst3-impls/host-context-proxy.cpp

@@ -18,6 +18,8 @@
 
 #include <iostream>
 
+#include <public.sdk/source/vst/hosting/hostclasses.h>
+
 Vst3HostContextProxyImpl::Vst3HostContextProxyImpl(
     Vst3Bridge& bridge,
     Vst3HostContextProxy::ConstructArgs&& args)
@@ -54,10 +56,48 @@ Vst3HostContextProxyImpl::getName(Steinberg::Vst::String128 name) {
 }
 
 tresult PLUGIN_API
-Vst3HostContextProxyImpl::createInstance(Steinberg::TUID cid,
+Vst3HostContextProxyImpl::createInstance(Steinberg::TUID /*cid*/,
                                          Steinberg::TUID _iid,
                                          void** obj) {
-    // TODO: Implement
+    // Class IDs don't have a meaning here, they just mirrored the interface
-    std::cerr << "TODO: IHostApplication::createInstance()" << std::endl;
+    // from `IPlugFactory::createInstance()`
-    return Steinberg::kNotImplemented;
+    constexpr size_t uid_size = sizeof(Steinberg::TUID);
+    if (!_iid || strnlen(_iid, uid_size) < uid_size) {
+        return Steinberg::kInvalidArgument;
+    }
+
+    Steinberg::FUID iid = Steinberg::FUID::fromTUID(_iid);
+    // If an objects wants to create an `IMessage` object to send it to some
+    // object it is directly connected to, then we can keep everything local
+    // on the Wine side. This is mostly an optimization, because it saves a
+    // lot of unnecessary back and forth communication.
+    if (are_objects_directly_connected) {
+        if (iid == Steinberg::Vst::IMessage::iid) {
+            // TODO: Add logging for this on verbosity level 1
+            *obj = new Steinberg::Vst::HostMessage{};
+            return Steinberg::kResultTrue;
+        } else if (iid == Steinberg::Vst::IAttributeList::iid) {
+            // TODO: Add logging for this on verbosity level 1
+            *obj = new Steinberg::Vst::HostAttributeList{};
+            return Steinberg::kResultTrue;
+        } else {
+            // When the host requests an interface we do not (yet) implement,
+            // we'll print a recognizable log message
+            const Steinberg::FUID uid = Steinberg::FUID::fromTUID(_iid);
+            std::cerr
+                << "TODO: Implement unknown interface logging on Wine side "
+                   "for Vst3HostContextProxyImpl::createInstance"
+                << std::endl;
+
+            return Steinberg::kNotImplemented;
+        }
+    } else {
+        // TODO: Implement for objects that are not directly connected
+        std::cerr
+            << "TODO: Creating <IMessage*> and <IAttributeList*> instances in "
+               "IHostApplication::createInstance() for indirectly "
+               "connected objects has not yet been implemented"
+            << std::endl;
+        return Steinberg::kNotImplemented;
+    }
 }