Re: scroll-bar-toolkit-scroll

[gerd.moellmann@t-online.de (Gerd Moellmann)]

Richard Stallman <rms@gnu.org> writes:

> scroll-bar-toolkit-scroll has no doc string; it needs one.  More
> importantly, I am concerned about what it does.  It is not
> compatible with the non-toolkit scroll commands.  What model
> was it designed to be compatible with?

None.

> I also wonder if it is being triggered at the proper time.
> Is it supposed to let you drag the handle?  To do that properly,
> it has to be activated on the down event, but that does not seem
> to be the case.  I can't really understand the comment in keyboard.c
> around line 5188; maybe it says that Emacs does not get a down event,
> or maybe only that Emacs can't distinguish down from up.  Which is it?

Scroll bar widgets work different from Emacs' scroll bars.  One
registers a callback function with the widget that is invoked when
actions happen on the scroll bar, for instance when the scroll bar
handle is dragged, when a scroll bar arrow is clicked etc.  The widget
does the translation of user actions to scroll bar actions, depending
on its capabilities and specified user translations (I mean the normal
X way of customizing X widgets).  The scroll bar actions received by
the callback function are converted to certain "widget events" that
are handled in Lisp.