From 2e28d5a885608fddd1e0b7464ba3c9582a9e8ca4 Mon Sep 17 00:00:00 2001
From: Tom Ryder <tom@sanctum.geek.nz>
Date: Fri, 24 Mar 2017 14:02:59 +1300
Subject: Add exm(1df) to work around Vim's screen-clearing

---
 README.markdown        |  1 +
 bin/exm                | 10 ++++++++++
 man/man1/exm.1df       | 22 ++++++++++++++++++++++
 sh/profile.d/editor.sh | 11 ++++++++++-
 4 files changed, 43 insertions(+), 1 deletion(-)
 create mode 100755 bin/exm
 create mode 100644 man/man1/exm.1df

diff --git a/README.markdown b/README.markdown
index 4cd4820c..8b95e1a9 100644
--- a/README.markdown
+++ b/README.markdown
@@ -469,6 +469,7 @@ Installed by the `install-bin` target:
     any options, mostly useful for scripts.
 *   `eds(1df)` edits executable script files in `EDSPATH`, defaulting to
     `~/.local/bin`, for personal scripting snippets.
+*   `exm(1df)` works around a screen-clearing quirk of Vim's `ex` mode.
 *   `finc(1df)` counts the number of results returned from a set of given
     `find(1)` conditions.
 *   `fnl(1df)` runs a command and saves its output and error into temporary
diff --git a/bin/exm b/bin/exm
new file mode 100755
index 00000000..cfae82d4
--- /dev/null
+++ b/bin/exm
@@ -0,0 +1,10 @@
+#!/bin/sh
+# If input is a terminal and ex(1) is the Vim version, force it to use a dumb
+# terminal so it doesn't clear the screen
+if [ -t 0 ] ; then
+    ver=$(ex --version | sed '1{s/ .*//;q}') 2>/dev/null
+    case $ver in
+        VIM) set -- -T builtin_dumb "$@" ;;
+    esac
+fi
+exec ex "$@"
diff --git a/man/man1/exm.1df b/man/man1/exm.1df
new file mode 100644
index 00000000..892ca326
--- /dev/null
+++ b/man/man1/exm.1df
@@ -0,0 +1,22 @@
+.TH EXM 1df "March 2017" "Manual page for exm"
+.SH NAME
+.B exm
+\- invoke Vim's ex(1) with a dumb terminal
+.SH SYNOPSIS
+.B exm
+[EX_OPTIONS...] [FILES]
+.SH DESCRIPTION
+.B exm
+works around a quirk of Vim that causes it to clear the screen when invoked as
+ex(1) interactively. It applies Vim's -T option to force the terminal to the
+builtin "dumb" terminal.
+.SH CAVEATS
+This doesn't work on its first invocation from any given terminal, but does
+work thereafter. I haven't yet figured out why.
+.P
+This breaks switching to visual mode with :visual somewhat, as the terminal
+will persist in its dumb state. I'm not sure there's a way to fix this. If
+there were a Vim :autocmd for mode switching, it might be possible, or perhaps
+by wrapping :visual somehow to :set terminal=$TERM.
+.SH AUTHOR
+Tom Ryder <tom@sanctum.geek.nz>
diff --git a/sh/profile.d/editor.sh b/sh/profile.d/editor.sh
index 5d6b249e..307879fe 100644
--- a/sh/profile.d/editor.sh
+++ b/sh/profile.d/editor.sh
@@ -1,7 +1,16 @@
-# Set command-line editor; ed if we've got it (!), but ex will do fine
+# Ideally, we'd use plain old ed(1), but many Linux distributions don't install
+# it by default
 if command -v ed >/dev/null 2>&1 ; then
     EDITOR=ed
+
+# Failing that, if we have both vim(1) and exm(1df) in our $PATH, use the
+# latter to work around Vim's ex mode screen-clearing
+elif { command -v vim && command -v exm ; } >/dev/null 2>&1 ; then
+    EDITOR=exm
+
+# Otherwise, just call ex(1) directly
 else
     EDITOR=ex
 fi
+
 export EDITOR
-- 
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