Re: [Pythoncad-developer] Undo functionality

[Matteo B. <mat...@bo...>]

You are right Yagnesh,

Even if we think of a pdm integration ... or erp .. this will help us
too mutch.

we can provide 3 additional column at the entity table:
date*revision*state

date :
could have null or a date 
if null we can delete the entity
if date have a value we can not delete (it's versionade)

revision: 
a number that indicate the revision
could be a str field in case the user use letter insted of nuber for
revision

starte:
Indicate the state of the entity released/undo_mark/... all we whant
in case the date field is not null the state is released


what do you think ?

Regards
Matteo


On Sun, 2010-02-07 at 08:04 +0530, Yagnesh Desai wrote:
> Gertwin;
> 
> I like the Idea. I think providing the facility of how drawing looked
> on a particular date is helpful, if we are able to tag that
> particular state of drawing as Major "Revision" then it would
> be very helpful.
> 
> All engineers use drawings as Rev 0, Rev 1, Rev 2 etc. All
> the intermediate states are not that important.
> 
> That is I can roll back to older "sensible" version and not
> the draft version of it.
> 
> - - - - - -
> Best regards
> Yagnesh Desai
> Save a tree...please don't print this e-mail.
> 
> 
> On Sat, Feb 6, 2010 at 11:51 PM,  <ger...@gm...> wrote:
> > Hi All,
> >
> > I was thinking about implementing undo functionality in combination with the
> > database.
> > I am not aware how this is solved in the current version but with a database
> > we can make the undo recording persistent (you can undo changes from a
> > previous drawing session).
> >
> > The idea is not to modify entities in the database but mark the old entity
> > state as deleted and insert a new record for the modified entity state.
> > Then there are two records in the database, one is the previous state and
> > one is the the current state of the entity.
> > Of course the entities that are marked as deleted (previous state) are not
> > drawn.
> >
> > When the user does undo the current state is marked as deleted and the
> > previous state is marked as not deleted.
> > A redo does this marking in the opposite direction.
> >
> > If we add a column "state" and a column "undo_mark" to our entity table we
> > can achieve this.
> > The column "state" holds the delete (or not) state.
> > The column "undo_mark" holds the value of the undo id.
> > Because the user can modify many entities at once all those entities get the
> > same "undo_mark".
> >
> > This way the history of the drawing is kept in the database and the user can
> > undo and redo actions from previous sessions.
> > If we also add a time stamp we even can provide functionality that will show
> > how the drawing looked at a certain date.
> >
> > I think this functionality can have some use and is something other CAD
> > programs does not always provide.
> > Undo and redo are simple database queries that are easy to implement.
> > We must keep the display list in sync with the state of the database but I
> > think this also it not difficult.
> >
> > We also need a function that compresses the drawing by removing the history.
> >
> > If it needs clarification, let me know I will try to explain.
> >
> > Do you think it is useful?
> >
> > Regards,
> > Gertwin
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