LibDSP: Allow ProcessorRangeParameter to specify if it's a log value

This doesn't affect the parameter's own behavior but is part of the
parameter meta-data, just as the name. If a parameter is logarithmic,
UI elements should represent it with an interface that scales
logarithmically.

Userland/Libraries/LibDSP/Effects.cpp

@@ -11,9 +11,9 @@ namespace LibDSP::Effects {
 
 Delay::Delay(NonnullRefPtr<Transport> transport)
     : EffectProcessor(move(transport))
-    , m_delay_decay("Decay"sv, 0.01, 0.99, 0.33)
-    , m_delay_time("Delay Time"sv, 3, 2000, 900)
-    , m_dry_gain("Dry"sv, 0, 1, 0.9)
+    , m_delay_decay("Decay"sv, 0.01, 0.99, 0.33, Logarithmic::No)
+    , m_delay_time("Delay Time"sv, 3, 2000, 900, Logarithmic::Yes)
+    , m_dry_gain("Dry"sv, 0, 1, 0.9, Logarithmic::No)
 {
 
     m_parameters.append(m_delay_decay);

Userland/Libraries/LibDSP/ProcessorParameter.h

@@ -26,6 +26,11 @@ enum class ParameterType : u8 {
     Boolean,
 };
 
+enum class Logarithmic : bool {
+    No,
+    Yes
+};
+
 // Processors have modifiable parameters that should be presented to the UI in a uniform way without requiring the processor itself to implement custom interfaces.
 class ProcessorParameter {
 public:
@@ -101,22 +106,25 @@ public:
 
 class ProcessorRangeParameter final : public Detail::ProcessorParameterSingleValue<ParameterFixedPoint> {
 public:
-    ProcessorRangeParameter(String name, ParameterFixedPoint min_value, ParameterFixedPoint max_value, ParameterFixedPoint initial_value)
+    ProcessorRangeParameter(String name, ParameterFixedPoint min_value, ParameterFixedPoint max_value, ParameterFixedPoint initial_value, Logarithmic logarithmic)
         : Detail::ProcessorParameterSingleValue<ParameterFixedPoint>(move(name), ParameterType::Range, move(initial_value))
         , m_min_value(move(min_value))
         , m_max_value(move(max_value))
         , m_default_value(move(initial_value))
+        , m_logarithmic(logarithmic)
     {
         VERIFY(initial_value <= max_value && initial_value >= min_value);
     }
 
     ProcessorRangeParameter(ProcessorRangeParameter const& to_copy)
-        : ProcessorRangeParameter(to_copy.name(), to_copy.min_value(), to_copy.max_value(), to_copy.value())
+        : ProcessorRangeParameter(to_copy.name(), to_copy.min_value(), to_copy.max_value(), to_copy.value(), to_copy.is_logarithmic())
     {
     }
 
     ParameterFixedPoint min_value() const { return m_min_value; }
     ParameterFixedPoint max_value() const { return m_max_value; }
+    ParameterFixedPoint range() const { return m_max_value - m_min_value; }
+    constexpr Logarithmic is_logarithmic() const { return m_logarithmic; }
     ParameterFixedPoint default_value() const { return m_default_value; }
     void set_value(ParameterFixedPoint value)
     {
@@ -128,6 +136,7 @@ private:
     double const m_min_value;
     double const m_max_value;
     double const m_default_value;
+    Logarithmic const m_logarithmic;
 };
 
 template<typename EnumT>

Userland/Libraries/LibDSP/Synthesizers.cpp

@@ -17,10 +17,10 @@ namespace LibDSP::Synthesizers {
 Classic::Classic(NonnullRefPtr<Transport> transport)
     : LibDSP::SynthesizerProcessor(transport)
     , m_waveform("Waveform"sv, Waveform::Saw)
-    , m_attack("Attack"sv, 0, 2000, 5)
-    , m_decay("Decay"sv, 0, 20'000, 80)
-    , m_sustain("Sustain"sv, 0, 1, 0.725)
-    , m_release("Release", 0, 6'000, 120)
+    , m_attack("Attack"sv, 0.01, 2000, 5, Logarithmic::Yes)
+    , m_decay("Decay"sv, 0.01, 20'000, 80, Logarithmic::Yes)
+    , m_sustain("Sustain"sv, 0.001, 1, 0.725, Logarithmic::No)
+    , m_release("Release", 0.01, 6'000, 120, Logarithmic::Yes)
 {
     m_parameters.append(m_waveform);
     m_parameters.append(m_attack);