Curtain effect is done
Fixed channel numbering for string and window models.
Changed behavior so that GenerateRandom is diabled during playback and
Graceful stop is the default button during playback.
Restore "HLS hlsIdata Sequences" to convert
Start of preview tab

not completed yet, but you can position display elements and save their
positions.
Preview now working

Repeat button and slider still to do
Preview Repeat button & slider now work

Tested with both music and animation sequences
Undo change to frame model
Fixed crash in preview
Fixed crash in RenderGridToSeqData()

Crash in RenderGridToSeqData() occurred when using custom start
channels.
Moved fix for "crash in preview" for better performance.
improvement for crash in preview fix