Add the ability to list the fonts detected

Adds a new CLI flag allowing the user to just list the fonts which are
detected on the system.

Signed-off-by: Rémy Greinhofer <remy.greinhofer@gmail.com>

crates/svg2pdf-cli/src/args.rs

@@ -6,10 +6,13 @@ use clap::Parser;
 #[clap(about, version)]
 pub struct Args {
     /// Path to read SVG file from.
-    pub input: PathBuf,
+    pub input: Option<PathBuf>,
     /// Path to write PDF file to.
     pub output: Option<PathBuf>,
     /// The number of SVG pixels per PDF points.
     #[clap(long, default_value = "72.0")]
     pub dpi: f32,
+    /// List the fonts available on the system.
+    #[clap(long)]
+    pub list_fonts: bool,
 }

crates/svg2pdf-cli/src/main.rs

@@ -20,16 +20,24 @@ fn main() {
 fn run() -> Result<(), String> {
     let args = args::Args::parse();
 
-    let name =
-        Path::new(args.input.file_name().ok_or("Input path does not point to a file")?);
+    // Prepare the font database.
+    let mut fontdb = fontdb::Database::new();
+    fontdb.load_system_fonts();
+
+    // List the fonts and exit.
+    if args.list_fonts {
+        list_fonts(&fontdb);
+        return Ok(());
+    }
+
+    // Or convert the file.
+    let input = args.input.expect("Input path must be specified");
+    let name = Path::new(input.file_name().ok_or("Input path does not point to a file")?);
     let output = args.output.unwrap_or_else(|| name.with_extension("pdf"));
 
-    let svg =
-        std::fs::read_to_string(&args.input).map_err(|_| "Failed to load SVG file")?;
+    let svg = std::fs::read_to_string(&input).map_err(|_| "Failed to load SVG file")?;
 
     let options = usvg::Options::default();
-    let mut fontdb = fontdb::Database::new();
-    fontdb.load_system_fonts();
 
     let mut tree = usvg::Tree::from_str(&svg, &options).map_err(|err| err.to_string())?;
     tree.convert_text(&fontdb);
@@ -54,3 +62,13 @@ fn print_error(msg: &str) -> io::Result<()> {
     w.reset()?;
     writeln!(w, ": {msg}.")
 }
+
+fn list_fonts(fontdb: &fontdb::Database) {
+    let mut faces: Vec<String> =
+        fontdb.faces().map(|f| f.post_script_name.clone()).collect();
+    faces.sort();
+    println!("Fonts found: {}", faces.len());
+    for face in faces {
+        println!("{face}")
+    }
+}