(* Copyright (C) 1992 Digital Equipment Corporation                          *)
(* All rights reserved.                                                      *)
(* See the file COPYRIGHT for a full description.                            *)
(*                                                                           *)
(* Last modified on Sat Jan  2 22:39:33 PST 1993 by meehan                   *)
<* PRAGMA LL *>

INTERFACE XtermModel;

IMPORT TextPortClass;

TYPE T <: TextPortClass.Model;

END XtermModel.

(* The Xterm model supports a single selection and mouse-events in the
   style of "xterm(1)".  It is a simple model; it is not
   ``programmable'', nor is it influenced by commands in the user's
   ".Xdefaults" file.

   The implementation supports only the primary selection, which
   corresponds to "VBT.Source" (the same as X's primary selection).

   A single-left-click establishes the keyboard focus and insertion
   point, but it does not change (acquire) the selection. A
   double-left-click selects the current word; a triple-left-click
   selects the current line. More clicks rotate among these three
   options.

   Single-left-click and drag selects a range of characters.
   Double-left-click and drag selects a range of words, and
   triple-left-click and drag selects a range of lines.

   Middle-click pastes the current source selection at the insertion
   point, which need not be at the end of the text (as it would be for
   a ``typescript'').  The xterm selection is never in replace-mode.

   Right-click extends the current selection, re-highlighting it if
   needed.

   The shift key has no effect on the mouse in xterm-mode; it is
   ignored, so that shift-left-click, for example, has the same effect
   as left-click.  The control and meta (``option'') keys, however,
   are not ignored; they cause the mouse-clicks to be no-ops, and they
   have different keybindings.  Control-left-click, for example, has
   no effect.

   The only keybindings that are supported are these:

\begin{center}
\begin{tabbing}
option-LongKeyName \= This is just a tab-setting line. \kill
 control-u    \> delete everything from the current position \\
              \> to the beginning of the line \\
 control-z    \> {\bf Undo} \\
 control-shift-z    \> {\bf Redo} \\
 meta-x       \> {\bf Cut} \\ 
 meta-c       \> {\bf Copy} \\
 meta-v       \> {\bf Paste}

\end{tabbing}
\end{center}

  "meta" refers to the "option" modifier.  Note that Copy does very
   little: as soon as there is a selection (e.g., via double-clicking
   or dragging the mouse), it automatically becomes the source
   selection; there is no separate clipboard in this model.
*)