Revise Param documentation. Fix Param::getDisplayValue() formula for logarithmic bases.

include/engine/Param.hpp

@@ -37,11 +37,10 @@ struct Param {
 	*/
 	std::string label;
 	/** The numerical unit of measurement appended to the value.
-	Use a space before non-abbreviations to separate the numerical value.
-	e.g. " semitones", "Hz", "%", "V"
+	Use a space before units to separate the numerical value from the number (e.g. " semitones", " Hz", " V"), unless the unit should have no space (e.g. "%", "º").
 	*/
 	std::string unit;
-	/** Set to 0 for linear, nonzero for exponential. */
+	/** Set to 0 for linear, positive for exponential, negative for logarithmic. */
 	float displayBase = 0.f;
 	float displayMultiplier = 1.f;
 	float displayOffset = 0.f;

src/app/ParamQuantity.cpp

@@ -85,7 +85,7 @@ void ParamQuantity::setDisplayValue(float displayValue) {
 	}
 	else if (displayBase < 0.f) {
 		// Logarithmic
-		v = std::pow(displayBase, v);
+		v = std::pow(-displayBase, v);
 	}
 	else {
 		// Exponential