HowTo: load CaptionElements into Silverlight Media Framework player

Trying to make CaptionsGridWindow of ClipFlair serve captions editing on-the-fly to SMF (Silverlight Media Framework [now called MMPPF]) player component, I had a real hard time, plagued by a bug at TimedTextElementStyle. It seems to be setting default FontSize for captions using a “Cell” unit instead of using a “Pixel” unit. Currently SMF only supports “Pixel” units at FontSize of TimedTextElements according to the codedoc notes.

Another issue I had was that CaptionRegion constructor sets it to be active all the time (specifying a Begin value of a min possible TimeExtent and an End value of the max possible TimeExtent), so it renders ShowBackground.WhenActive setting useless for it. That is if you want the captions background to show up only when there are captions showing (active), then you have to set the CaptionRegion’s background to Colors.Transparent and set each CaptionElement’s background to some non-transparent color (note that both CaptionRegion and CaptionElement are TimedTextElements, with the later added to the former’s Children property, forming a TimedTree that is).

 

public void UpdateMarkers(MediaMarkerCollection<TimedTextElement> newMarkers)
 {
   if (newMarkers == null) return;

   CaptionRegion  region = new CaptionRegion();
   region.Style.ShowBackground = ShowBackground.WhenActive; 
             //doesn't seem to work if other than transparent color is used
   region.Style.BackgroundColor = Colors.Transparent;

   foreach (CaptionElement marker in newMarkers)
   {
     region.Children.Add(marker);
     marker.CaptionElementType = TimedTextElementType.Text;
     marker.Style.ShowBackground = ShowBackground.WhenActive;
     marker.Style.BackgroundColor = Color.FromArgb(100, 0, 0, 0); 
                                       //use a semi-transparent background
     marker.Style.Color = Colors.White;
     //marker.Style.TextAlign = TextAlignment.Center;
     Length length = new Length
     {
       Unit = LengthUnit.Pixel, 
       Value = 20
     }; //must use this, since the default LengthUnit.Cell used
        //at TimedTextStyle constructor is not supported
     marker.Style.FontSize = length;
   }

   Captions.Add(region);
}