Add --no-syntax-highlight and --theme options

This patch adds two new command-line options for the rich text viewer:
--no-syntax-highlight and --theme.  --no-syntax-highlight disables the
syntax highlighting for code snippets.  --theme selects a color theme
for the syntax highlighting.

CHANGELOG.md

@@ -10,6 +10,8 @@ SPDX-License-Identifier: MIT
 - Add syntax highlighting:
   - Add syntax highlighting using `syntect` for code snippets displayed with
     the rich text viewer.
+  - Add the `--no-syntax-highlight` option to disable syntax highlighting.
+  - Add the `--theme [theme]` option to select the syntax highlighting theme.
 
 ## v0.1.3 (2020-07-28)
 

src/main.rs

@@ -99,7 +99,21 @@ struct Opt {
 }
 
 #[derive(Debug, StructOpt)]
-pub struct ViewerArgs {}
+pub struct ViewerArgs {
+    /// Disable syntax highlighting.
+    ///
+    /// Per default, rusty-man tries to highlight Rust code snippets in its output if the rich text
+    /// viewer is selected.  If this option is set, it renders the HTML representation instead.
+    #[structopt(long)]
+    no_syntax_highlight: bool,
+
+    /// The color theme for syntax highlighting
+    ///
+    /// rusty-man includes these color themes: base16-ocean.dark, base16-eighties.dark,
+    /// base16-mocha.dark, base16-ocean.light, InspiredGitHub, Solarized (dark), Solarized (light).
+    #[structopt(long, default_value = "base16-eighties.dark")]
+    theme: String,
+}
 
 fn main() -> anyhow::Result<()> {
     env_logger::init();

src/viewer/text/mod.rs

@@ -11,8 +11,8 @@ use std::marker;
 use crate::doc;
 use crate::viewer;
 
-pub trait Printer: fmt::Debug {
-    fn new(args: crate::ViewerArgs) -> Self;
+pub trait Printer: fmt::Debug + marker::Sized {
+    fn new(args: crate::ViewerArgs) -> anyhow::Result<Self>;
 
     fn print_title(&self, left: &str, middle: &str, right: &str) -> io::Result<()>;
 
@@ -48,7 +48,7 @@ impl<P: Printer> TextViewer<P> {
     {
         spawn_pager();
 
-        let printer = P::new(args);
+        let printer = P::new(args)?;
         let renderer = TextRenderer::new(printer);
         op(&renderer).or_else(ignore_pipe_error).map_err(Into::into)
     }

src/viewer/text/plain.rs

@@ -20,10 +20,10 @@ struct Decorator {
 }
 
 impl super::Printer for PlainTextRenderer {
-    fn new(_args: crate::ViewerArgs) -> Self {
-        Self {
+    fn new(_args: crate::ViewerArgs) -> anyhow::Result<Self> {
+        Ok(Self {
             line_length: viewer::get_line_length(),
-        }
+        })
     }
 
     fn print_title(&self, left: &str, middle: &str, right: &str) -> io::Result<()> {

src/viewer/text/rich.rs

@@ -13,8 +13,9 @@ type RichString = text_renderer::TaggedString<Vec<text_renderer::RichAnnotation>
 #[derive(Debug)]
 pub struct RichTextRenderer {
     line_length: usize,
+    highlight: bool,
     syntax_set: syntect::parsing::SyntaxSet,
-    theme_set: syntect::highlighting::ThemeSet,
+    theme: syntect::highlighting::Theme,
 }
 
 impl RichTextRenderer {
@@ -53,12 +54,20 @@ impl RichTextRenderer {
 }
 
 impl super::Printer for RichTextRenderer {
-    fn new(_args: crate::ViewerArgs) -> Self {
-        Self {
+    fn new(args: crate::ViewerArgs) -> anyhow::Result<Self> {
+        use anyhow::Context;
+
+        let mut theme_set = syntect::highlighting::ThemeSet::load_defaults();
+        let theme = theme_set
+            .themes
+            .remove(&args.theme)
+            .with_context(|| format!("Could not find theme {}", &args.theme))?;
+        Ok(Self {
             line_length: viewer::get_line_length(),
+            highlight: !args.no_syntax_highlight,
             syntax_set: syntect::parsing::SyntaxSet::load_defaults_newlines(),
-            theme_set: syntect::highlighting::ThemeSet::load_defaults(),
-        }
+            theme,
+        })
     }
 
     fn print_title(&self, left: &str, middle: &str, right: &str) -> io::Result<()> {
@@ -87,9 +96,9 @@ impl super::Printer for RichTextRenderer {
     }
 
     fn print_code(&self, indent: usize, code: &doc::Text) -> io::Result<()> {
+        if self.highlight {
             let syntax = self.syntax_set.find_syntax_by_extension("rs").unwrap();
-        let theme = &self.theme_set.themes["base16-eighties.dark"];
-        let mut h = syntect::easy::HighlightLines::new(syntax, theme);
+            let mut h = syntect::easy::HighlightLines::new(syntax, &self.theme);
 
             for line in syntect::util::LinesWithEndings::from(&code.plain) {
                 let ranges = h.highlight(line, &self.syntax_set);
@@ -97,6 +106,9 @@ impl super::Printer for RichTextRenderer {
                 self.render_syntax(&ranges)?;
             }
             writeln!(io::stdout())?;
+        } else {
+            self.print_html(indent, code, false)?;
+        }
 
         Ok(())
     }