Add optional value_to_normalized

This version of value_to_optimized checks whether the resulting value is in range and returns an option containing Some(value) if it is, and None if it isn't.

src/utils/mod.rs

@@ -66,6 +66,32 @@ impl ValueScaling {
         }
         .clamp(0., 1.)
     }
+
+    pub fn value_to_normalized_optional(&self, value: f32, min: f32, max: f32) -> Option<f32> {
+        let unmap = |x: f32| -> f32 { (x - min) / (max - min) };
+
+        let value = match self {
+            ValueScaling::Linear => unmap(value),
+
+            ValueScaling::Power(exponent) => unmap(value).powf(1.0 / *exponent),
+
+            ValueScaling::Frequency => {
+                let minl = min.log2();
+                let range = max.log2() - minl;
+                (value.log2() - minl) / range
+            }
+
+            ValueScaling::Decibels => unmap({
+                const CONVERSION_FACTOR: f32 = std::f32::consts::LOG10_E * 20.0;
+                value.ln() * CONVERSION_FACTOR
+            }),
+        };
+        if (0.0..=1.0).contains(&value) {
+            Some(value)
+        } else {
+            None
+        }
+    }
 }
 
 // We can't use impl_res_simple!() since we're using nih_plug's version of VIZIA