DefaultMediaTheme: Properly set control targets.

In removing the "GroupView" class and replacing it with a real BGroupView,
I missed that it its AttachedToWindow() implementation iterated over all
child controls and set their targets to themselves. It seems this is how
the Media Kit gets change messages from them, and so the lack of this
broke changing parameter values. Whoops.

But it seems that changing menu option values has been broken for a long time
(perhaps forever?), as in order for a BOptionPopUp to send messages to anything,
its AttachedToWindow() must be called (as this sets the BMenuItem's targets
to itself, so it can forward the messages.) So now that is fixed too.

src/kits/media/DefaultMediaTheme.cpp

@@ -169,9 +169,14 @@ static void
 start_watching_for_parameter_changes(BControl* control, BParameter &parameter)
 {
 	BMediaRoster* roster = BMediaRoster::CurrentRoster();
-	if (roster != NULL) {
+	if (roster == NULL)
-		roster->StartWatching(control, parameter.Web()->Node(),
+		return;
-			B_MEDIA_NEW_PARAMETER_VALUE);
+
+	if (roster->StartWatching(control, parameter.Web()->Node(),
+			B_MEDIA_NEW_PARAMETER_VALUE) != B_OK) {
+		fprintf(stderr, "DefaultMediaTheme: Failed to start watching parameter"
+			"\"%s\"\n", parameter.Name());
+		return;
 	}
 }
 
@@ -180,11 +185,12 @@ static void
 stop_watching_for_parameter_changes(BControl* control, BParameter &parameter)
 {
 	BMediaRoster* roster = BMediaRoster::CurrentRoster();
-	if (roster != NULL) {
+	if (roster == NULL)
+		return;
+
 	roster->StopWatching(control, parameter.Web()->Node(),
 		B_MEDIA_NEW_PARAMETER_VALUE);
 }
-}
 
 
 //	#pragma mark -
@@ -296,6 +302,9 @@ CheckBox::~CheckBox()
 void
 CheckBox::AttachedToWindow()
 {
+	BCheckBox::AttachedToWindow();
+
+	SetTarget(this);
 	start_watching_for_parameter_changes(this, fParameter);
 }
 
@@ -323,6 +332,9 @@ OptionPopUp::~OptionPopUp()
 void
 OptionPopUp::AttachedToWindow()
 {
+	BOptionPopUp::AttachedToWindow();
+
+	SetTarget(this);
 	start_watching_for_parameter_changes(this, fParameter);
 }
 
@@ -350,6 +362,9 @@ Slider::~Slider()
 void
 Slider::AttachedToWindow()
 {
+	BSlider::AttachedToWindow();
+
+	SetTarget(this);
 	start_watching_for_parameter_changes(this, fParameter);
 }
 
@@ -377,9 +392,10 @@ ChannelSlider::~ChannelSlider()
 void
 ChannelSlider::AttachedToWindow()
 {
-	start_watching_for_parameter_changes(this, fParameter);
-
 	BChannelSlider::AttachedToWindow();
+
+	SetTarget(this);
+	start_watching_for_parameter_changes(this, fParameter);
 }