Instant apply and explicit apply in KDE HIG

[Ellen Reitmayr]

On Friday, 3. March 2006 17:28, Diego Moya wrote:
> On 03/03/06, Gábor Lehel <illissius at gmail.com> wrote:
> > On 3/3/06, Ellen Reitmayr <ellen at kde.org> wrote:
> > > On OpenUsability, Stefan Monov suggested to promote the usage of
> > > instant apply instead of explicit apply in certain situations in KDE
>
> an improved workflow, instant apply has the additional advantage of
> *forcing* the system to have an undo facility (which is good for the
> user, as it allows an exploratory use of the interface). 

Force? No, it's still in the hands of the developer. 
For example, MacOSX colour settings (e.g. desktop background) is instant apply 
and does not have an undo function. There are other examples on MacOSX I 
won't list now.

> The worse 
> part of "Apply" buttons is that they are destructive - once used, you
> can never recover the previous state. I'll always prefer a "Revert all
> changes" button to an "Apply" one in a dialog.
If there is an undo function, you can also undo an applied action. 

The existance of a history system is in the hands of the developer (or the 
libs), it is not dependent on the type of apply.



> If you are controlling a physical property (like size or position),
> you probably would be better by changing it directly (with drag and
> drop) instead of doing it through a related property box. This is
> Direct Manipulation at its best.

Don't tell that a graphic designer -> they usually use the numeric value to 
make 100% equal alignment ;-)

However: The spin box in a graphical application was just an example for a 
situation where the revert mechanisms for instant apply have to be considered 
carefully. 

There are many things to decide:
Spin box -> save history when user changes direction, previous state or timer?
Colour space -> save history when user stops to move the mouse, previous state 
or timer?
Slider -> Same?
Text input -> Apply as you type or explicitly confirm via return?
 .... 
(there is more when you really start to think about it)


Cheers,
/el






-- 

Ellen Reitmayr
KDE Usability Project
usability.kde.org