Blender Git Loki

== Sequencer ==

Attention! Rather large sequencer rewrite:

* Implemented layer blending using implicit effects. (works like layers
in "The Gimp" or Photoshop.)
* Fixed Space-Bar start-stop in preview windows.
You can start playback using spacebar within a preview-window and it _works_!
* Fixed Flip Y (didn't work for float)
* Fixed premul (didn't work for float)
* Added IPOs to _all_ tracks. In blend-mode REPLACE it drives the
"mul"-parameter in all other blend modes it drives the effect.
* you can meta single tracks.
* moved "mute track" from "M" to "Shift-M"
* added "Shift-L" for "lock track"
* changed inner workings for Metas. Now all ImBufs have to use the
reference counting mechanism. (Only interesting for coders :)

!!! Really important change, that affects current files!

Since you can mute tracks and now there is real layer blending capabilities
in place, I changed the silly behaviour that chose the output track.

Old behaviour: if we have an effect track visible, use the uppermost effect
track. If there is _no_ effect track visible, use the lowest input track.

New behaviour: always use the uppermost track. With blend modes active:
work our way down starting from the uppermost track to the first
"replace"-mode track. This is the way the gimp, photoshop, basically _all_
other applications work...

So if this change ruins your day: please try to fix your files using
"mute". If this doesn't work out, I can still restore the old behaviour,
but I really hope, that this is _not_ necessary!

Rational: most people won't get affected by this change, since you can't
really do anything usefull with the (old) sequencer without at least one
effect track and then you are on the safe side...