Initial commit: InstaLPEQ linear phase EQ plugin

Full-featured linear phase EQ with interactive graphical curve display.
FIR-based processing (8192-tap), 8 parametric bands, multi-platform
CI/CD (Windows/macOS/Linux), InstaDrums visual style.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

Source/PluginProcessor.cpp

@@ -0,0 +1,196 @@
+#include "PluginProcessor.h"
+#include "PluginEditor.h"
+
+InstaLPEQProcessor::InstaLPEQProcessor()
+    : AudioProcessor (BusesProperties()
+                          .withInput  ("Input",  juce::AudioChannelSet::stereo(), true)
+                          .withOutput ("Output", juce::AudioChannelSet::stereo(), true))
+{
+}
+
+InstaLPEQProcessor::~InstaLPEQProcessor()
+{
+    firEngine.stop();
+}
+
+bool InstaLPEQProcessor::isBusesLayoutSupported (const BusesLayout& layouts) const
+{
+    if (layouts.getMainInputChannelSet()  != juce::AudioChannelSet::stereo() ||
+        layouts.getMainOutputChannelSet() != juce::AudioChannelSet::stereo())
+        return false;
+    return true;
+}
+
+void InstaLPEQProcessor::prepareToPlay (double sampleRate, int samplesPerBlock)
+{
+    currentSampleRate = sampleRate;
+    currentBlockSize = samplesPerBlock;
+
+    juce::dsp::ProcessSpec spec { sampleRate, (juce::uint32) samplesPerBlock, 2 };
+    convolution.prepare (spec);
+
+    firEngine.start (sampleRate);
+    updateFIR();
+
+    setLatencySamples (firEngine.getLatencySamples());
+}
+
+void InstaLPEQProcessor::releaseResources()
+{
+    firEngine.stop();
+    convolution.reset();
+}
+
+void InstaLPEQProcessor::processBlock (juce::AudioBuffer<float>& buffer, juce::MidiBuffer&)
+{
+    juce::ScopedNoDenormals noDenormals;
+
+    // Check for new FIR from background thread
+    if (auto newFIR = firEngine.getNewFIR())
+    {
+        convolution.loadImpulseResponse (std::move (*newFIR), currentSampleRate,
+                                          juce::dsp::Convolution::Stereo::no,
+                                          juce::dsp::Convolution::Trim::no,
+                                          juce::dsp::Convolution::Normalise::no);
+        firLoaded = true;
+    }
+
+    if (bypassed.load() || ! firLoaded)
+        return;
+
+    // Process through convolution
+    juce::dsp::AudioBlock<float> block (buffer);
+    juce::dsp::ProcessContextReplacing<float> context (block);
+    convolution.process (context);
+
+    // Apply master gain
+    float gain = juce::Decibels::decibelsToGain (masterGainDb.load());
+    if (std::abs (gain - 1.0f) > 0.001f)
+        buffer.applyGain (gain);
+}
+
+// ============================================================
+// Band management
+// ============================================================
+
+std::vector<EQBand> InstaLPEQProcessor::getBands() const
+{
+    const juce::SpinLock::ScopedLockType lock (bandLock);
+    return bands;
+}
+
+void InstaLPEQProcessor::setBand (int index, const EQBand& band)
+{
+    {
+        const juce::SpinLock::ScopedLockType lock (bandLock);
+        if (index >= 0 && index < (int) bands.size())
+            bands[index] = band;
+    }
+    updateFIR();
+}
+
+void InstaLPEQProcessor::addBand (float freq, float gainDb)
+{
+    {
+        const juce::SpinLock::ScopedLockType lock (bandLock);
+        if ((int) bands.size() >= maxBands)
+            return;
+        EQBand b;
+        b.frequency = freq;
+        b.gainDb = gainDb;
+        bands.push_back (b);
+    }
+    updateFIR();
+}
+
+void InstaLPEQProcessor::removeBand (int index)
+{
+    {
+        const juce::SpinLock::ScopedLockType lock (bandLock);
+        if (index >= 0 && index < (int) bands.size())
+            bands.erase (bands.begin() + index);
+    }
+    updateFIR();
+}
+
+int InstaLPEQProcessor::getNumBands() const
+{
+    const juce::SpinLock::ScopedLockType lock (bandLock);
+    return (int) bands.size();
+}
+
+void InstaLPEQProcessor::updateFIR()
+{
+    auto currentBands = getBands();
+    firEngine.setBands (currentBands);
+}
+
+// ============================================================
+// State save/restore
+// ============================================================
+
+void InstaLPEQProcessor::getStateInformation (juce::MemoryBlock& destData)
+{
+    juce::XmlElement xml ("InstaLPEQ");
+    xml.setAttribute ("bypass", bypassed.load());
+    xml.setAttribute ("masterGain", (double) masterGainDb.load());
+
+    auto currentBands = getBands();
+    for (int i = 0; i < (int) currentBands.size(); ++i)
+    {
+        auto* bandXml = xml.createNewChildElement ("Band");
+        bandXml->setAttribute ("freq", (double) currentBands[i].frequency);
+        bandXml->setAttribute ("gain", (double) currentBands[i].gainDb);
+        bandXml->setAttribute ("q", (double) currentBands[i].q);
+        bandXml->setAttribute ("type", (int) currentBands[i].type);
+        bandXml->setAttribute ("enabled", currentBands[i].enabled);
+    }
+
+    copyXmlToBinary (xml, destData);
+}
+
+void InstaLPEQProcessor::setStateInformation (const void* data, int sizeInBytes)
+{
+    auto xml = getXmlFromBinary (data, sizeInBytes);
+    if (xml == nullptr || ! xml->hasTagName ("InstaLPEQ"))
+        return;
+
+    bypassed.store (xml->getBoolAttribute ("bypass", false));
+    masterGainDb.store ((float) xml->getDoubleAttribute ("masterGain", 0.0));
+
+    std::vector<EQBand> loadedBands;
+    for (auto* bandXml : xml->getChildIterator())
+    {
+        if (! bandXml->hasTagName ("Band"))
+            continue;
+
+        EQBand b;
+        b.frequency = (float) bandXml->getDoubleAttribute ("freq", 1000.0);
+        b.gainDb = (float) bandXml->getDoubleAttribute ("gain", 0.0);
+        b.q = (float) bandXml->getDoubleAttribute ("q", 1.0);
+        b.type = static_cast<EQBand::Type> (bandXml->getIntAttribute ("type", 0));
+        b.enabled = bandXml->getBoolAttribute ("enabled", true);
+        loadedBands.push_back (b);
+    }
+
+    {
+        const juce::SpinLock::ScopedLockType lock (bandLock);
+        bands = loadedBands;
+    }
+    updateFIR();
+}
+
+// ============================================================
+// Editor
+// ============================================================
+
+juce::AudioProcessorEditor* InstaLPEQProcessor::createEditor()
+{
+    return new InstaLPEQEditor (*this);
+}
+
+// This creates new instances of the plugin
+juce::AudioProcessor* JUCE_CALLTYPE createPluginFilter()
+{
+    return new InstaLPEQProcessor();
+}