Re: custom-declare-variable

[Luc Teirlinck]

Kim Storm wrote:

   I've seen little evidence that anybody is actually using custom themes
   in its current form, so it can hardly be an "important feature" that
   should uphold the release.

Maybe it might be good to give an overview of the presently available
alternatives to Custom Themes and what their advantages and
disadvantages are compared to Custom themes.  From this comparison, it
would appear that Custom Themes fill a need and are worth
implementing, but it also makes it is obvious that there is no sense
in rushing them hastily into Emacs 22.

There is the reportedly widely used and popular color-theme.el.  I
believe that color-themes can not be disabled.  They use setq and setq
does not work well with Custom.

Global minor modes can be used as themes.  They have the big advantage
of being _total_ customization themes, working for keybindings and
other stuff, as well as for user options.  They can be disabled.  To
properly disable the mode, the mode has to store the current value of
an option when it changes it, to restore it when the mode is disabled.
That works OK, because the option's value is usually essential to the
proper functioning of the minor mode, so the user should not change it
while the minor mode is enabled.  Minor modes use setq, but in this
case, this is probably ideal, because Custom will and _should_ tell
the user that customizing the option may not work as expected.  This
seems to be the case with cua-mode, for instance, which sets
transient-mark-mode to t and which, if I understand correctly, makes
not much sense without that.

So what would be the advantages of (properly implemented) Custom
themes?  In as far as I see it, there is are only two (closely
related) advantages.  Firstly, unlike color-themes, Custom Themes work
well with Custom.  Secondly, they can not only be disabled (minor
modes can too), but, unlike with global minor modes, the user can
safely override the values they set with other themes or through
Custom (but not using setq).  Themes and Custom store information
allowing for proper conflict resolution (setq does not).  (These
advantages apply to _properly implemented_ Custom Themes, not to
whatever the current code is trying to implement.)

The advantage only exists if conflict resolution is implemented in a
100% accurate and intuitive fashion.  There is no sense in Custom
Themes that more or less work.  People will not use them if they do
not work 100%.  They will use color-theme.el or global minor modes.

Sincerely,

Luc.