Fix ddc brightness not applying because process exits before debounce timer runs (#2217)

* Fix ddc brightness not applying because process exits before debounce timer runs

* Added sync.WaitGroup to DDCBackend and use it instead of loop in wait logic, added timeout in case i2c hangs.

* go fmt

---------

Co-authored-by: bbedward <bbedward@gmail.com>

core/internal/server/brightness/ddc.go

@@ -218,7 +218,9 @@ func (b *DDCBackend) SetBrightnessWithExponent(id string, value int, exponential
 	if timer, exists := b.debounceTimers[id]; exists {
 		timer.Reset(200 * time.Millisecond)
 	} else {
+		b.debounceWg.Add(1)
 		b.debounceTimers[id] = time.AfterFunc(200*time.Millisecond, func() {
+			defer b.debounceWg.Done()
 			b.debounceMutex.Lock()
 			pending, exists := b.debouncePending[id]
 			if exists {
@@ -490,5 +492,19 @@ func (b *DDCBackend) valueToPercent(value int, max int, exponential bool) int {
 	return percent
 }
 
+func (b *DDCBackend) WaitPending() {
+	done := make(chan struct{})
+	go func() {
+		b.debounceWg.Wait()
+		close(done)
+	}()
+
+	select {
+	case <-done:
+	case <-time.After(5 * time.Second):
+		log.Debug("WaitPending timed out waiting for DDC writes")
+	}
+}
+
 func (b *DDCBackend) Close() {
 }

core/internal/server/brightness/types.go

@@ -84,6 +84,7 @@ type DDCBackend struct {
 	debounceMutex   sync.Mutex
 	debounceTimers  map[string]*time.Timer
 	debouncePending map[string]ddcPendingSet
+	debounceWg      sync.WaitGroup
 }
 
 type ddcPendingSet struct {