logarithmic scaling added; missing the step fn for now

src/config.rs

@@ -18,6 +18,7 @@ pub struct KnobConfig {
     pub(crate) max_angle: f32,
     pub(crate) reset_value: Option<f32>,
     pub(crate) allow_scroll: bool,
+    pub(crate) logarithmic_scaling: bool,
 }
 
 impl KnobConfig {
@@ -39,7 +40,8 @@ impl KnobConfig {
             show_background_arc: true,
             show_filled_segments: true,
             reset_value: None,
-            allow_scroll:false
+            allow_scroll:false,
+            logarithmic_scaling: false,
         }
     }
 }