linenoise: visual select and clipboard copy/paste.

* linenoise/linenoise.c (struc lino_state): New member,
clip, sel, end, dsel, dend, need_refresh, selmode.
(sync_data_to_buf): Update the sel and end members
of the structure based on dsel and dend, the way
pos is being updated from dpos.
(refresh_singleline, refresh_multiline): If visual selection
mode is in effect, show the selected region in inverse video.
(update_sel, clear_sel, yank_sel, delete_sel):
New static function.
(edit_insert): Delete the selection before inserting, so that
the character appears to replace the selection.
Set need_refresh flag instead of calling refresh_line.
(edit_insert_str): New static function. Inserts string,
replacing existing selection, if any.
(paren_jump, edit_move_left, edit_move_right, edit_move_home,
edit_move_end, edit_history_next): Set new
need_refresh flag instead of calling refresh_line directly.
(edit_delete): If selection is in effect, just delete the
selection and return. Set need_refresh flag instead
of calling refresh_line.
(edit_backspace): If selection is in effect, and selection
is not inverted (cursor is to the right of selection)
then just delete the selection. Otherwise delete the
selection, and perform the backspace. Set need_refresh flag
instead of calling refresh_line.
(edit_delete_prev_word): Delete the selection and the word
before the selection. Set need_refresh flag
instead of calling refresh_line.
(edit_in_editor): Set need_refresh_flag instead of
calling refresh_line, and cancel visual selection mode.
(edit): Clear selection mode on entry. Update the selection
variables on each loop iteration. Honor the need_refresh
flag. New commands implemented: Ctrl-S, Ctrl-Q, Ctrl-X Ctrl-Q.
Some commands need to set need_refresh flag.
Some need to cancel selection mode.
(lino_copy): Set the clip member of the cloned structure
to null, otherwise there will be a double free of the
clipboard buffer.
(lino_cleanup): Free the clipboard and null out the pointer.

* txr.1: Documented visual select.

1 files changed, 101 insertions, 0 deletions

diff --git a/txr.1 b/txr.1
index 937432a3..8a0e59d1 100644
--- a/txr.1
+++ b/txr.1
@@ -33821,6 +33821,107 @@ when written out to the file. Conversely, when the edited file is read
 back, its newlines are converted to carriage returns, so that multi-line
 content is handled properly. (See the following section, Multi-Line Mode).
 
+.SS* Visual Selection Mode
+
+The interactive listener supports visual copy and paste operation.
+Text may be visually selected for copying into a clipboard (copy)
+or deletion. In visual selection mode, the actions of some editing
+commands are modified so that they act upon the selection instead
+of their usual target, or upon both the target and the selection.
+
+.NP* Making a Selection
+
+The Ctrl-S command enters into visual selection mode and marks the
+starting point of the selection, which is considered the position
+immediately to the left of the current character.
+
+While in visual selection mode, it is possible to move around using
+the usual movement commands. The ending point of the selection
+tracks the movement. The ending point of the selection is also
+the position immediately to the left of the current character.
+Thus the selection excludes the rightmost character. The selection
+consists of the text between these two positions, whether or not
+they are reversed. The selected text is displayed in reverse video.
+
+Typing Ctrl-S again while in visual selection mode cancels
+the mode.
+
+Tab completion, history navigation, history search and editing in an external
+editor all cancel visual selection mode.
+
+.NP* Visual Copy
+
+The Ctrl-Y command ("yank") copies the selected text into a clipboard buffer.
+The previous contents of the clipboard buffer, if any, are discarded.
+
+Unlike the history, the clipboard buffer is not persisted.
+If \*(TX terminates, it is lost.
+
+.NP* Visual Cut
+
+If the Ctrl-D command is invoked while a selection is in effect, then
+instead of deleting the character under the cursor, it deletes the
+selection, and copies it to the clipboard.
+
+.NP* Clipboard Paste
+
+The Ctrl-Q command ("quote the clipboard") inserts text from the clipboard
+at the current cursor position. The cursor position is updated to
+be immediately after the inserted text.  The clipboard text remains available
+for further pasting.
+
+If nothing has been yet been copied to the clipboard in the current
+session, then this command has no effect.
+
+.NP* Clipboard Swap Paste
+
+The Ctrl-X, Ctrl-Q command sequence ("exchange quote") exchanges the
+selected text with the contents of the clipboard. The selection is
+copied into the clipboard as if by Ctrl-Y and replaced by the
+previous contents of the clipboard.
+
+If the clipboard has not yet been used in the current session,
+
+If nothing has been yet been copied to the clipboard in the current
+session, then this command behaves like Ctrl-Y:
+text is yanked into the clipboard, but not deleted.
+
+.NP* Visual Replace
+
+In visual selection mode, an editing commands may be used which insert new
+text, or a character may be typed in order to insert it. When this happens, the
+selection is first deleted and visual mode is canceled. Then the insertion
+takes place and visual mode is canceled. The effect is that the newly inserted
+text replaces the selected text.
+
+This applies to the Clipboard Paste (Ctrl-Q) command also. If a
+selection is effect when Ctrl-Q is invoked, the selected text
+is replaced with the clipboard buffer contents.
+
+When a selection is replaced, nothing is copied to the clipboard.
+
+.NP* Delete in Selection Mode
+
+In visual mode, it is possible to issue commands which delete text.
+Ctrl-D has special behavior, Visual Cut, described above.
+
+The Backspace key and Ctrl-H also have a special behavior in select mode. If
+the cursor is at the rightmost endpoint of the selection, then these commands
+delete the selection and nothing else.  If the cursor is at the leftmost
+endpoint of the selection, then these commands delete the selection, and take
+their usual effect of deleting a character also.  In both cases, selection mode
+is canceled.
+
+The Ctrl-W command to delete the previous word, wen used in visual
+selection mode, deletes the selection and cancels selection mode,
+and then deletes the word before the selection.
+
+All other deletion commands such as Ctrl-K simply cancel visual
+selection mode and take their usual effect.
+
+Nothing is copied to the clipboard when deletion commands are used while a
+selection is in effect.
+
 .SS* Multi-Line Mode
 
 The listener operates in one of two modes: line mode and multi-line mode.