[Lazarus] Groundwork for Undo in Form Designer

[Juha Manninen]

Hi,

I haven't actually got any feedback about my patch, neither here nor in issue 
tracker. All the discussion was about const array syntax.

Designer Undo should be done in many steps.

1. Forward commands to right places. My patch does that. 

2. Undo for move and resize. This should be easy because there is no 
dependency to other forms or controls. This covers already ~45% of use cases 
(number taken from my hat).

3. Undo for delete control. This is more difficult because of dependencies and 
because the deleted control can be a container with more controls in it. This 
covers another ~45% of use cases. Besides, Undo could really save your day 
when you delete controls by accident.

4. Rest of it. ~10% of use cases. Attribute changes triggered in different 
ways. Adding controls. Full undo support in every situation is not necessary, 
for example when reading / changing binary data in some property.

If I work with this feature I need my patches applied in steps. I have seen 
that Lazarus SVN gets many patches every day. Development is incremental.
I don't want to build some isolated big patch either, which might finally get 
rejected because it clashes with the project's architecture in some way I 
didn't notice.
I understood from Mattias Gärtner's mail that he is busy. Is there anyone else 
that could check IDE related patches?

Currently I would have both time and motivation for open source stuff. Things 
can change if I get a new job or if my studies become more demanding.


Regards,
Juha Manninen