From 67fe8042567254d21c82ecda9f116745e2438fc2 Mon Sep 17 00:00:00 2001
From: sharkdp <davidpeter@web.de>
Date: Mon, 23 Dec 2019 09:54:18 +0100
Subject: [PATCH] Do not pass '--no-init' on newer less versions

With this change, we do not pass the `--no-init` option in newer
versions of less (530 or higher).

This fixes #749
---
 src/less.rs   | 49 +++++++++++++++++++++++++++++++++++++++++++++++++
 src/lib.rs    |  1 +
 src/output.rs | 14 +++++++++++++-
 3 files changed, 63 insertions(+), 1 deletion(-)
 create mode 100644 src/less.rs

diff --git a/src/less.rs b/src/less.rs
new file mode 100644
index 00000000..d7c60f2a
--- /dev/null
+++ b/src/less.rs
@@ -0,0 +1,49 @@
+use std::process::Command;
+
+pub fn retrieve_less_version() -> Option<usize> {
+    let cmd = Command::new("less").arg("--version").output().ok()?;
+    parse_less_version(&cmd.stdout)
+}
+
+fn parse_less_version(output: &[u8]) -> Option<usize> {
+    if output.starts_with(b"less ") {
+        let version = std::str::from_utf8(&output[5..]).ok()?;
+        let end = version.find(' ')?;
+        version[..end].parse::<usize>().ok()
+    } else {
+        None
+    }
+}
+
+#[test]
+fn test_parse_less_version_487() {
+    let output = b"less 487 (GNU regular expressions)
+Copyright (C) 1984-2016  Mark Nudelman
+
+less comes with NO WARRANTY, to the extent permitted by law.
+For information about the terms of redistribution,
+see the file named README in the less distribution.
+Homepage: http://www.greenwoodsoftware.com/less";
+
+    assert_eq!(Some(487), parse_less_version(output));
+}
+
+#[test]
+fn test_parse_less_version_551() {
+    let output = b"less 551 (PCRE regular expressions)
+Copyright (C) 1984-2019  Mark Nudelman
+
+less comes with NO WARRANTY, to the extent permitted by law.
+For information about the terms of redistribution,
+see the file named README in the less distribution.
+Home page: http://www.greenwoodsoftware.com/less";
+
+    assert_eq!(Some(551), parse_less_version(output));
+}
+
+#[test]
+fn test_parse_less_version_wrong_program() {
+    let output = b"more from util-linux 2.34";
+
+    assert_eq!(None, parse_less_version(output));
+}
diff --git a/src/lib.rs b/src/lib.rs
index 04e3b63a..e6743644 100644
--- a/src/lib.rs
+++ b/src/lib.rs
@@ -24,6 +24,7 @@ mod decorations;
 mod diff;
 pub mod dirs;
 pub mod inputfile;
+mod less;
 pub mod line_range;
 mod output;
 mod preprocessor;
diff --git a/src/output.rs b/src/output.rs
index 8cf39118..c4d70c90 100644
--- a/src/output.rs
+++ b/src/output.rs
@@ -7,6 +7,7 @@ use std::process::{Child, Command, Stdio};
 use shell_words;
 
 use crate::errors::*;
+use crate::less::retrieve_less_version;
 use crate::PagingMode;
 
 #[derive(Debug)]
@@ -70,10 +71,21 @@ impl OutputType {
                 let mut process = if is_less {
                     let mut p = Command::new(&pager_path);
                     if args.is_empty() || replace_arguments_to_less {
-                        p.args(vec!["--RAW-CONTROL-CHARS", "--no-init"]);
+                        p.arg("--RAW-CONTROL-CHARS");
                         if quit_if_one_screen {
                             p.arg("--quit-if-one-screen");
                         }
+
+                        // Passing '--no-init' fixes a bug with '--quit-if-one-screen' in older
+                        // versions of 'less'. Unfortunately, it also breaks mouse-wheel support.
+                        //
+                        // See: http://www.greenwoodsoftware.com/less/news.530.html
+                        match retrieve_less_version() {
+                            Some(version) if version < 530 => {
+                                p.arg("--no-init");
+                            }
+                            _ => {}
+                        }
                     } else {
                         p.args(args);
                     }