support lookups via language servers (LSP)

* The main interface is the `FT` command.
  `FT` was an undocumented Video TECO command for etags/ctags lookups.
  I don't want to exactly copy its interface, though.
* `FT` allows looking up symbol names,
  definitions and references.
* ctags will be supported via ctags-lsp.
  LSP support is more powerful though and works without
  regenerating TAGS files all the time.
  The LSP will also allow you to customize auto-completions
  using SciTECO itself (i.e. by writing a language server
  in SciTECO).
* For multiple results, `FT$` can be used to cycle through
  results - this should mimic repeated `S$` or `N$`.
* `:FT...$` does a fuzzy search. IMHO it's not important
  to return a status integer instead. `FT` will only
  really be used in interactive mode.
* Document synchronization is supported via hooks from
  ring.c and via Scintilla notifications.
* Currently, the LSP communication is based on blocking
  GIOChannels. This means that a misbehaving hanging
  server could "lock up" the entire editor (FIXME).
  Only on ncurses you can always kill the subprocess by
  pressing CTRL+C.
  We need helper functions in spawn.c to read and write
  with interruptions.
* The textDocument/didChange notification transmits
  not only all edits, but all files' contents as well
  during initial synchronization.
  Therefore it is optimized to write and JSON-escape
  data without copying them around in memory and without
  destroying the buffer gap.
* Use $SCITECO_LSP to configure the language server.
  You can also use `tee` to capture stdin and stdout.
  Perhaps $SCITECO_LSP should be saved in .teco_session,
  so you can change it between projects?
* $SCITECO_LSP_ROOT is used to point to the project's
  root directory. session.tes will set it up automatically.

1 files changed, 10 insertions, 0 deletions

diff --git a/doc/sciteco.1.in b/doc/sciteco.1.in
index 9b4b112..858bf6d 100644
--- a/doc/sciteco.1.in
+++ b/doc/sciteco.1.in
@@ -391,6 +391,16 @@ for an example of how to integrate the X11 clipboard via
 Integrating with Wayland and the Mac OS clipboards is of course also possible.
 .
 .LP
+.SCITECO_TOPIC "$SCITECO_LSP" "$SCITECO_LSP_ROOT"
+The \fBSCITECO_LSP\fP environment variable must be set to a language
+server command line if you would like to use the \fBFT\fP command for looking up
+symbols, definitions or references.
+The language server spawning works with UNIX98 shell emulation as well (bit 8
+in \fBED\fP flags), but will otherwise use the shell from \fBSHELL\fP or \fBCOMSPEC\fP.
+\fBSCITECO_LSP_ROOT\fP can be set to the root directory of the language server's
+workspace (defaults to current directory at the time of spawning).
+.
+.LP
 .SCITECO_TOPIC "$GTK_CSD"
 \# NOTE: Contrary to the GTK documentation, this is _not_ supported
 \# natively yet. We have to implement it ourselves.