Add logging facility

Cargo.toml

@@ -12,7 +12,8 @@ readme = "README.md"
 license = "MIT OR Apache-2.0"
 
 [workspace.dependencies]
-svg2pdf = { path = ".", version = "0.9.1", default-features = false }
+log = "0.4.20"
+svg2pdf = { path = ".", default-features = false, version = "0.9.1" }
 clap = { version = "4.4.2", features = ["derive"] }
 clap_complete = "4.4.3"
 clap_mangen = "0.2.14"
@@ -52,6 +53,7 @@ miniz_oxide = { workspace = true }
 once_cell = { workspace = true }
 pdf-writer = { workspace = true }
 usvg = { workspace = true }
+log = { workspace = true }
 image = { workspace = true, optional = true }
 tiny-skia = {workspace = true, optional = true}
 resvg = {workspace = true, optional = true}

cli/Cargo.toml

@@ -22,6 +22,7 @@ doc = false
 clap = { workspace = true }
 fontdb = { workspace = true }
 image = { workspace = true }
+log = { workspace = true }
 miniz_oxide = { workspace = true }
 pdf-writer = { workspace = true }
 svg2pdf = { workspace = true }

cli/src/convert.rs

@@ -12,6 +12,10 @@ pub fn convert_(
     output: Option<PathBuf>,
     dpi: f32,
 ) -> Result<(), String> {
+    if let Ok(()) = log::set_logger(&LOGGER) {
+        log::set_max_level(log::LevelFilter::Warn);
+    }
+
     // Prepare the font database.
     let mut fontdb = fontdb::Database::new();
     fontdb.load_system_fonts();
@@ -39,3 +43,44 @@ pub fn convert_(
 
     Ok(())
 }
+
+// Taken from resvg
+/// A simple stderr logger.
+static LOGGER: SimpleLogger = SimpleLogger;
+struct SimpleLogger;
+impl log::Log for SimpleLogger {
+    fn enabled(&self, metadata: &log::Metadata) -> bool {
+        metadata.level() <= log::LevelFilter::Warn
+    }
+
+    fn log(&self, record: &log::Record) {
+        if self.enabled(record.metadata()) {
+            let target = if !record.target().is_empty() {
+                record.target()
+            } else {
+                record.module_path().unwrap_or_default()
+            };
+
+            let line = record.line().unwrap_or(0);
+            let args = record.args();
+
+            match record.level() {
+                log::Level::Error => {
+                    eprintln!("Error (in {}:{}): {}", target, line, args)
+                }
+                log::Level::Warn => {
+                    eprintln!("Warning (in {}:{}): {}", target, line, args)
+                }
+                log::Level::Info => eprintln!("Info (in {}:{}): {}", target, line, args),
+                log::Level::Debug => {
+                    eprintln!("Debug (in {}:{}): {}", target, line, args)
+                }
+                log::Level::Trace => {
+                    eprintln!("Trace (in {}:{}): {}", target, line, args)
+                }
+            }
+        }
+    }
+
+    fn flush(&self) {}
+}

src/render/group.rs

@@ -24,6 +24,11 @@ pub fn render(
         return;
     }
 
+    #[cfg(not(feature = "filters"))]
+    if !group.filters().is_empty() {
+        log::warn!("Filters have been disabled in this build of svg2pdf.")
+    }
+
     let initial_opacity = initial_opacity.unwrap_or(Opacity::ONE);
 
     // Filters will be ignored

src/render/mod.rs

@@ -67,7 +67,9 @@ impl Render for Node {
                 ctx,
             ),
             #[cfg(not(feature = "image"))]
-            Node::Image(_) => {},
+            Node::Image(_) => {
+                log::warn!("Images have been disabled in this build of svg2pdf.")
+            }
             Node::Text(ref text) => {
                 group::render(
                     text.flattened(),

tests/src/lib.rs

@@ -1,6 +1,5 @@
 #[rustfmt::skip]
 mod library;
-mod cli;
 
 use std::cmp::max;
 use std::fs;