On 29-Nov-2002, RaphaŽl Quinet wrote:
> However, here is my point of view (which may be different from what
> some other developers think, so do not take this for granted).  There
> are two kinds of "grouping":
> - Simple linking of layers so that some operations such as toggling
>   their visibility or moving the whole group of layers can easily be
>   applied to them (bug #86337, bug #86277).  These operations would 
>   not modify the pixels in the layers.  This could probably also be
>   used for implementing the clipping groups (bug #51112).
> - Grouping of layers in such a way that a merged image of the layers
>   is stored in a virtual layer and some operations can be applied to
>   this merged layer: color adjustments, transformations or even any
>   PDB operation, including the ones done by a plug-in.  Whenever a
>   layer in the group is modified, the merged image is rebuilt and the
>   operation associated with it is applied to in order to re-create the
>   updated "active layer".  This can be used to implement the Photoshop
>   styles or adjustment layers (bug #79025, bug #98262).  In summary,
>   the "active layer" would have a list of layers, a drawable and one
>   PDB function (with its current parameters) associated with it.
>   Whenever something happens to one of the layers in the list, a new
>   (invisible) drawable is allocated, it gets the merged copy of all
>   layers, and then the PDB function is applied to it.  When the
>   results are ready, the new drawable replaces the one that was
>   visible.  In some cases, it may be better to keep the two drawables
>   (merged view + results) and to apply the PDB function only to the
>   regions that have been modified, but this is only an optimization.
> So as you mentioned yourself, there are two ways to define "groups":
> they have different purposes and need to be implemented differently.

That is a _perfect_ explination of what I want. =)

Patrick "Diablo-D3" McFarland || [EMAIL PROTECTED]
"Computer games don't affect kids; I mean if Pac-Man affected us as kids, we'd 
all be running around in darkened rooms, munching magic pills and listening to
repetitive electronic music." --Kristian Wilson, Nintendo, Inc, 1989

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