Most raster applications allows the user to lock a layer, and some allow alpha-locking. Thus we need to specify how to express this in OpenRaster.
There seem to me to be 3 kinds of locking:
1. Edit locking: if ON, prevents the layer from being edited in any way. This may also prevent it from being selected or picked from, but that's a detail for implementations.
2. Alpha locking: if ON, new data can only be written where alpha is nonzero, and the alpha of a pixel cannot be changed.
3. Positional locking (linking): if ON, and the layer is moved relative to other layers, then any other position-locked layers move in unison with it.
It seems to me that 1 and 2 are the important concepts. Any others?
Layer edit locking proposal written and up for review:
Mailing list discussion kicked off:
I'm not going to bother trying to specify alpha-locking status or positional locking because MyPaint doesn't implement them currently. I've suggested a possible syntax for these (very marginally) related concepts and left it at that.
alpha-locking -> bug 47815
positional-locking -> bug 47816
They're different concepts, so create separate bugs for them and retitle. Assign the remainder to myself since I'm currently seeking consensus on this via the mailing list.
We have both rough consensus on the list and running code for this. At this point it's just the schema that needs updating and some final tidyup on the specification draft. Could someone review and merge
on Oct 24, 2016 at 20:04:47.
(provided by the Example extension).