internal/pipewire: respond to Core::Ping

There is currently no known message that will get the PipeWire server to emit this event. It should be handled regardless.

Signed-off-by: Ophestra <cat@gensokyo.uk>

internal/pipewire/core.go

@@ -6,6 +6,7 @@ import (
 	"maps"
 	"slices"
 	"strconv"
+	"syscall"
 	"time"
 )
 
@@ -615,6 +616,14 @@ func (e *UnknownBoundIdError[E]) Error() string {
 	return "unknown bound proxy id " + strconv.Itoa(int(e.Id))
 }
 
+// An InvalidPingError is a [CorePing] event targeting a proxy id that was never allocated.
+type InvalidPingError CorePing
+
+func (e *InvalidPingError) Error() string {
+	return "received Core::Ping seq " + strconv.Itoa(int(e.Sequence)) +
+		" targeting unknown proxy id " + strconv.Itoa(int(e.ID))
+}
+
 func (core *Core) consume(opcode byte, files []int, unmarshal func(v any)) error {
 	closeReceivedFiles(files...)
 	switch opcode {
@@ -637,6 +646,23 @@ func (core *Core) consume(opcode byte, files []int, unmarshal func(v any)) error
 		// anything, and this behaviour is never mentioned in documentation
 		return nil
 
+	case PW_CORE_EVENT_PING:
+		var ping CorePing
+		unmarshal(&ping)
+		if _, ok := core.ctx.proxy[ping.ID]; ok {
+			core.ctx.mustWriteMessage(PW_ID_CORE, (*CorePong)(&ping))
+			return nil
+		} else {
+			invalidPingError := InvalidPingError(ping)
+			core.ctx.mustWriteMessage(PW_ID_CORE, &CoreErrorMethod{CoreError{
+				ID:       PW_ID_CORE,
+				Sequence: core.ctx.currentRemoteSeq(),
+				Result:   -Int(syscall.EINVAL),
+				Message:  invalidPingError.Error(),
+			}})
+			return &invalidPingError
+		}
+
 	case PW_CORE_EVENT_ERROR:
 		var coreError CoreError
 		unmarshal(&coreError)