Re: An Emacs plug-in for a browser (Firefox?)

[Richard M. Stallman]

    Emacs has the concept that two windows can look at the same
    buffer.

Displaying a buffer containing an XEmbed in two Emacs windows ought to
work work -- perhaps only because it would not mean what one might
expect.

Suppose you put an XEmbed widget into an Emacs buffer (perhaps with a
special kind of `display' property on part of the text) and display
the buffer in a window.  As with any other thing in the Emacs buffer,
Emacs has to know how tall it should appear.  You would have to
specify this, in the `display' property I suppose.  Then when Emacs
displays that buffer in the window, it will show part of the XEmbed if
appropriate, just as it might show all or part of an image in the
buffer.

It should not be hard for Emacs to do this in two windows in parallel,
if it can make the other program display into a pixmap of the
specified size.

Note that scrolling an Emacs window will not tell the other program
anything.  It will just tell Emacs to display a different part of the
appearance of the buffer in that window.

I think that people have a different behavior in mind for the browser:
namely to hand over a particular Emacs window to the browser and
expecting it to use the whole of that window, knowing the size of that
window.

That would be a different kind of feature.  Instead of having an
XEmbed widget in the text in a buffer, it would mean having a buffer
that is simply an alias for displaying the output of another program.
So if you tell an Emacs window to display that buffer, it really means
to telling the other program to use and control that Emacs window.

It would be hard to do that in more than one window, unless the other
program supports multiple windows.  If it does, it ought to be able to
handle two Emacs windows in parallel the same way it would handle two
other windows in parallel.  Most graphical browsers seem to be able to
do this.

Another way to handle doing this in two windows at once is to run two
copies of the program in parallel.  That might be ok for some simple
programs.