From 96cc391f2d5865ba256d61b823c50225fc12e7e2 Mon Sep 17 00:00:00 2001
From: sharkdp <davidpeter@web.de>
Date: Sat, 19 May 2018 10:31:10 +0200
Subject: [PATCH] Skip '--quit-if-one-screen' for --paging=always

closes #97
---
 src/app.rs  | 27 +++++++++++++++++++++------
 src/main.rs | 35 +++++++++++++++++++++--------------
 2 files changed, 42 insertions(+), 20 deletions(-)

diff --git a/src/app.rs b/src/app.rs
index a2625e11..228add91 100644
--- a/src/app.rs
+++ b/src/app.rs
@@ -181,16 +181,24 @@ impl App {
                 Some("never") => false,
                 Some("auto") | _ => self.interactive_output,
             },
-            paging: match self.matches.value_of("paging") {
-                Some("always") => true,
-                Some("never") => false,
+            paging_mode: match self.matches.value_of("paging") {
+                Some("always") => PagingMode::Always,
+                Some("never") => PagingMode::Never,
                 Some("auto") | _ => if files.contains(&None) {
                     // If we are reading from stdin, only enable paging if we write to an
                     // interactive terminal and if we do not *read* from an interactive
                     // terminal.
-                    self.interactive_output && !atty::is(Stream::Stdin)
+                    if self.interactive_output && !atty::is(Stream::Stdin) {
+                        PagingMode::QuitIfOneScreen
+                    } else {
+                        PagingMode::Never
+                    }
                 } else {
-                    self.interactive_output
+                    if self.interactive_output {
+                        PagingMode::QuitIfOneScreen
+                    } else {
+                        PagingMode::Never
+                    }
                 },
             },
             term_width: Term::stdout().size().1 as usize,
@@ -230,13 +238,20 @@ impl App {
     }
 }
 
+#[derive(Debug, Clone, Copy)]
+pub enum PagingMode {
+    Always,
+    QuitIfOneScreen,
+    Never,
+}
+
 pub struct Config<'a> {
     pub true_color: bool,
     pub output_wrap: OutputWrap,
     pub output_components: OutputComponents,
     pub language: Option<&'a str>,
     pub colored_output: bool,
-    pub paging: bool,
+    pub paging_mode: PagingMode,
     pub term_width: usize,
     pub files: Vec<Option<&'a str>>,
     pub theme: Option<&'a str>,
diff --git a/src/main.rs b/src/main.rs
index 104c1b27..2ee8d6f0 100644
--- a/src/main.rs
+++ b/src/main.rs
@@ -37,7 +37,7 @@ use syntect::easy::HighlightLines;
 use syntect::highlighting::Theme;
 use syntect::parsing::SyntaxDefinition;
 
-use app::App;
+use app::{App, PagingMode};
 use assets::{config_dir, syntax_set_path, theme_set_path, HighlightingAssets};
 use diff::get_git_diff;
 use printer::Printer;
@@ -59,12 +59,27 @@ enum OutputType {
 }
 
 impl OutputType {
-    fn pager() -> Result<Self> {
-        Ok(OutputType::Pager(Command::new("less")
-            .args(&["--quit-if-one-screen", "--RAW-CONTROL-CHARS", "--no-init"])
+    fn from_mode(mode: PagingMode) -> Self {
+        use PagingMode::*;
+        match mode {
+            Always => OutputType::try_pager(false),
+            QuitIfOneScreen => OutputType::try_pager(true),
+            _ => OutputType::stdout(),
+        }
+    }
+
+    /// Try to launch the pager. Fall back to stdout in case of errors.
+    fn try_pager(quit_if_one_screen: bool) -> Self {
+        let mut args = vec!["--RAW-CONTROL-CHARS", "--no-init"];
+        if quit_if_one_screen {
+            args.push("--quit-if-one-screen");
+        }
+        Command::new("less")
+            .args(&args)
             .stdin(Stdio::piped())
             .spawn()
-            .chain_err(|| "Could not spawn pager")?))
+            .map(OutputType::Pager)
+            .unwrap_or_else(|_| OutputType::stdout())
     }
 
     fn stdout() -> Self {
@@ -153,14 +168,6 @@ fn print_file(
     Ok(())
 }
 
-fn get_output_type(paging: bool) -> OutputType {
-    if paging {
-        OutputType::pager().unwrap_or_else(|_| OutputType::stdout())
-    } else {
-        OutputType::stdout()
-    }
-}
-
 fn run() -> Result<()> {
     let app = App::new();
 
@@ -243,7 +250,7 @@ fn run() -> Result<()> {
                 return Ok(());
             }
 
-            let mut output_type = get_output_type(config.paging);
+            let mut output_type = OutputType::from_mode(config.paging_mode);
             let handle = output_type.handle()?;
             let mut printer = Printer::new(handle, &config);