[Lazarus] Undo for Form Designer

[Mattias Gaertner]

On Tue, 29 Dec 2009 00:53:03 +0200
Juha Manninen <juha.manninen at phnet.fi> wrote:

> Hi,
> 
> there are at least 2 request issues for undo feature for the form designer.
> I always dreamt of such a feature in Delphi but it still hasn't got one.
> In Lazarus it would be nice.

True.

 
> I guess other people have thought of it, too. How to implement it? Where to 
> hook the code for undo? Maybe there is even experimental code for it 
> somewhere. I would like to know about the detailed ideas if there are any.

There is no experimental code yet.

Notes:
Changing a property (e.g. Left) changes some other properties too and
there is no hook. So for undo you must store the whole form plus the
descendant forms plus the referenced forms plus the source changes. This
costs much time and memory. For example with some images you easily get
a megabyte.
So it would be unwise to create an undo step on every change. 
 

Mattias