Handle different image file formats

deltamap.toml

 [sources.OSM]
 max_zoom = 19
 url_template = "http://a.tile.openstreetmap.org/{z}/{x}/{y}.png"
+extension = "png"

src/config.rs

 struct Source {
     max_zoom: u32,
     url_template: String,
+    extension: String,
 }
 
 impl Config {
                     id as u32,
                     source.url_template.clone(),
                     path,
+                    source.extension.clone(),
                     source.max_zoom,
                 ),
             ));

src/main.rs

     let mut sources = TileSources::new(config.tile_sources()).unwrap();
 
     let mut window = glutin::WindowBuilder::new().build().unwrap();
-    window.set_title("DeltaMap");
+    window.set_title(&("DeltaMap - ".to_string() + sources.current_name()));
     window.set_window_resize_callback(Some(resize_callback as fn(u32, u32)));
     let _ = unsafe { window.make_current() };
 
 
     'outer: for event in window.wait_events() {
         let mut start_loop = Instant::now();
+        let start_source_id = sources.current().id();
 
         let mut redraw = false;
 
             let diff = start_loop.elapsed();
             println!("EVENT LOOP SECS {}", diff.as_secs() as f64 + f64::from(diff.subsec_nanos()) * 1e-9);
         }
+
+        // set window title
+        if sources.current().id() != start_source_id {
+            window.set_title(&("DeltaMap - ".to_string() + sources.current_name()));
+        }
     }
 }
 
         &self.sources[self.current_index].1
     }
 
+    pub fn current_name(&self) -> &str {
+        &self.sources[self.current_index].0
+    }
+
     pub fn switch_to_next(&mut self) {
         self.current_index = (self.current_index + 1) % self.sources.len();
     }

src/tile_loader.rs

     {
         let mut client_opt = None;
         while let Ok((tile, url, path, write_to_file)) = request_rx.recv() {
-            println!("work {:?}", tile);
+            println!("work {:?} {:?}", tile, path);
             match image::open(&path) {
                 Ok(img) => {
                     result_tx.send((tile, Some(img))).unwrap();

src/tile_source.rs

     id: u32,
     url_template: String,
     directory: PathBuf,
+    extension: String,
     max_zoom: u32,
 }
 
         id: u32,
         url_template: S,
         directory: P,
+        extension: String,
         max_zoom: u32,
     ) -> Self {
         TileSource {
             id: id,
             url_template: url_template.into(),
             directory: directory.into(),
+            extension: extension,
             max_zoom: max_zoom,
         }
     }
         let mut path = PathBuf::from(&self.directory);
         path.push(tile_coord.zoom.to_string());
         path.push(tile_coord.x.to_string());
-        path.push(tile_coord.y.to_string() + ".png");
+        path.push(tile_coord.y.to_string() + "." + &self.extension);
 
         path
     }