[Lazarus] Testing 0.9.29

[Hans-Peter Diettrich]

Mattias Gaertner schrieb:

>> In the most useful model every control would have its own (configurable) 
>> layout manager, selectable from an (extensible) number of predefined 
>> layouts. In fact the DockManager already *is* such an *installable* 
>> layout manager...
> 
> A TDockmanager is somewhat more.

Not really. Every container can act as a DockSite, this is not a 
privilege or special feature of an DockManager. All methods involved in 
the *act* of docking can reside in the TDragDockObjects, as implemented 
in Delphi, instead of the currently used DragPerformers. Also the 
distinction between Controls[] and DockClients[] is nonsense, because 
only one of these collections can contain elements, at the same time 
(both properties could be rebased onto the same field).

> But I think a TLCLLayoutManager could be done similar to this. Maybe
> TDockManager should be made a descendant of a TLCLLayoutManager.

Right. I already tried such an approach, and failed due to the existing 
dependencies between a general layout manager and the already introduced 
AnchorSides, ChildSizing etc. fields - these and all related methods 
should be moved into specialized layout managers.

A control only needs a reference to its layout manager, and eventually 
another (untyped) reference to layout data, created and used exclusively 
by that layout manager. Such a design would e.g. allow to transform the 
currently distributed AnchorSides into kind of that tree, that currently 
has to be built from scratch, whenever a site with (such) anchors is 
updated (during autosizing...).

DoDi