Add a way to retrieve clap_event_header_t*s

This sets the correct pointer in the SysEx events just before returning
them.

src/common/serialization/clap/events.cpp

@@ -16,6 +16,8 @@
 
 #include "events.h"
 
+#include "../../utils.h"
+
 namespace clap {
 namespace events {
 
@@ -106,5 +108,25 @@ std::optional<Event> Event::parse(const clap_event_header_t& generic_event) {
     }
 }
 
+const clap_event_header_t* Event::get() const {
+    return std::visit(
+        overload{[](payload::MidiSysex& event) -> const clap_event_header_t* {
+                     // These events contain heap data pointers. We store this
+                     // data using an `std::string` alongside the event struct,
+                     // but we can only set the pointer here just before
+                     // returning the event in case it was moved inbetween
+                     // deserialization and this function being called.
+                     event.event.buffer =
+                         reinterpret_cast<const uint8_t*>(event.buffer.data());
+                     event.event.size = event.buffer.size();
+
+                     return &event.event.header;
+                 },
+                 [](const auto& event) -> const clap_event_header_t* {
+                     return &event.event.header;
+                 }},
+        payload);
+}
+
 }  // namespace events
 }  // namespace clap

src/common/serialization/clap/events.h

@@ -238,6 +238,12 @@ struct alignas(16) Event {
      */
     static std::optional<Event> parse(const clap_event_header_t& generic_event);
 
+    /**
+     * Get the `clap_event_header_t*` representation for this event. The pointer
+     * is valid as long as this struct isn't moved.
+     */
+    const clap_event_header_t* get() const;
+
     /**
      * The actual event data. These also contain the header because storing the
      * entire `clap_event_*_t` struct is the only way to serialize the event
@@ -247,19 +253,20 @@ struct alignas(16) Event {
      * `clap_input_events::get()`, but that would cause unexpected lifetime
      * issues.
      */
-    std::variant<payload::Note,
-                 payload::NoteExpression,
-                 payload::ParamValue,
-                 payload::ParamMod,
-                 payload::ParamGesture,
-                 // Most events are about the same length, but having the
-                 // transport in here sadly doubles this struct's size
-                 // TODO: Pack the events at some point, this will require
-                 //       special handling for SysEx events
-                 payload::Transport,
-                 payload::Midi,
-                 payload::MidiSysex,
-                 payload::Midi2>
+    mutable std::variant<
+        payload::Note,
+        payload::NoteExpression,
+        payload::ParamValue,
+        payload::ParamMod,
+        payload::ParamGesture,
+        // Most events are about the same length, but having the transport in
+        // here sadly doubles this struct's size
+        // TODO: Pack the events at some point, this will require special
+        //       handling for SysEx events
+        payload::Transport,
+        payload::Midi,
+        payload::MidiSysex,
+        payload::Midi2>
         payload;
 
     template <typename S>