Jan/fix forcing lfo change

complete/tremolo_plugin/include/Tremolo/Tremolo.h

@@ -1,18 +1,16 @@
 #pragma once
 
 namespace tremolo {
+enum class ApplySmoothing { no, yes };
+
 class Tremolo {
 public:
   enum class LfoWaveform : size_t {
     sine = 0,
     triangle = 1,
   };
 
-  Tremolo() {
-    for (auto& lfo : lfos) {
-      lfo.setFrequency(5.f /* Hz */, true);
-    }
-  }
+  Tremolo() { setModulationRateHz(5.f, ApplySmoothing::no); }
 
   void prepare(double sampleRate, int expectedMaxFramesPerBlock) {
     const juce::dsp::ProcessSpec processSpec{
@@ -31,16 +29,24 @@ class Tremolo {
     lfoSamples.resize(4u * static_cast<size_t>(expectedMaxFramesPerBlock));
   }
 
-  void setModulationRate(float rateHz) noexcept {
+  void setModulationRateHz(
+      float rateHz,
+      ApplySmoothing applySmoothing = ApplySmoothing::yes) noexcept {
+    const auto force = applySmoothing == ApplySmoothing::no;
     for (auto& lfo : lfos) {
-      lfo.setFrequency(rateHz);
+      lfo.setFrequency(rateHz, force);
     }
   }
 
-  void setLfoWaveform(LfoWaveform waveform) {
+  void setLfoWaveform(LfoWaveform waveform,
+                      ApplySmoothing applySmoothing = ApplySmoothing::yes) {
     jassert(waveform == LfoWaveform::sine || waveform == LfoWaveform::triangle);
 
     lfoToSet = waveform;
+
+    if (applySmoothing == ApplySmoothing::no) {
+      currentLfo = waveform;
+    }
   }
 
   void process(juce::AudioBuffer<float>& buffer) noexcept {
@@ -118,9 +124,14 @@ class Tremolo {
   static constexpr auto modulationDepth = 0.4f;
 
   static float triangle(float phase) {
+    // offset the phase by pi/2 to return 0 if phase equals 0
+    // and match the sine waveform
+    // (otherwise, the waveform starts at 1)
+    const auto offsetPhase = phase - juce::MathConstants<float>::halfPi;
+
     // Source:
     // https://thewolfsound.com/sine-saw-square-triangle-pulse-basic-waveforms-in-synthesis/#triangle
-    const auto ft = phase / juce::MathConstants<float>::twoPi;
+    const auto ft = offsetPhase / juce::MathConstants<float>::twoPi;
     return 4.f * std::abs(ft - std::floor(ft + 0.5f)) - 1.f;
   }
 
@@ -146,7 +157,10 @@ class Tremolo {
   }
 
   std::array<juce::dsp::Oscillator<float>, 2u> lfos{
-      juce::dsp::Oscillator<float>{[](auto phase) { return std::sin(phase); }},
+      juce::dsp::Oscillator<float>{[](auto phase) {
+        // start phase is -pi -> change it to 0 to match the mathematical sine
+        return std::sin(phase + juce::MathConstants<float>::pi);
+      }},
       juce::dsp::Oscillator<float>{triangle}};
 
   LfoWaveform currentLfo = LfoWaveform::sine;

complete/tremolo_plugin/source/PluginProcessor.cpp

@@ -1,4 +1,5 @@
 
+#include "tremolo_plugin/include/Tremolo/Tremolo.h"
 namespace tremolo {
 PluginProcessor::PluginProcessor()
     : AudioProcessor(
@@ -107,16 +108,26 @@ void PluginProcessor::processBlock(juce::AudioBuffer<float>& buffer,
     buffer.clear(channelToClear, 0, buffer.getNumSamples());
   }
 
+  const auto bypassedAndNotTransitioning =
+      parameters.bypassed.get() && !bypassTransitionSmoother.isTransitioning();
+  const auto applySmoothing =
+      bypassedAndNotTransitioning ? ApplySmoothing::no : ApplySmoothing::yes;
+
   // update the parameters
-  tremolo.setModulationRate(parameters.rate);
+  // Skip smoothing if fully bypassed to avoid LFO waveform morphing
+  // when parameters change under bypass ON.
+  // For example, if the LFO waveform is the sine, and the user selects
+  // the triangle under bypass ON, they will see a curved triangle slope
+  // on toggling bypass OFF, which is unexpected.
+  tremolo.setModulationRateHz(parameters.rate, applySmoothing);
   tremolo.setLfoWaveform(
-      static_cast<Tremolo::LfoWaveform>(parameters.waveform.getIndex()));
+      static_cast<Tremolo::LfoWaveform>(parameters.waveform.getIndex()),
+      applySmoothing);
 
   bypassTransitionSmoother.setBypass(parameters.bypassed);
 
-  if (parameters.bypassed.get() &&
-      !bypassTransitionSmoother.isTransitioning()) {
-    // avoid processing if the plugin is bypassed
+  if (bypassedAndNotTransitioning) {
+    // avoid processing if the plugin is fully bypassed
     return;
   }
 
@@ -153,7 +164,16 @@ void PluginProcessor::setStateInformation(const void* data, int sizeInBytes) {
     DBG(result.getErrorMessage());
   }
 
+  // Skip smoothing to avoid LFO waveform morphing
+  // when loading a project or a preset.
+  // For example, the default LFO waveform is the sine. If the project or preset
+  // has the triangle selected, the user will see a curved triangle slope
+  // on load, which is unexpected.
   bypassTransitionSmoother.setBypassForced(parameters.bypassed);
+  tremolo.setLfoWaveform(
+      static_cast<Tremolo::LfoWaveform>(parameters.waveform.getIndex()),
+      ApplySmoothing::no);
+  tremolo.setModulationRateHz(parameters.rate, ApplySmoothing::no);
 }
 
 Parameters& PluginProcessor::getParameterRefs() noexcept {