From 4748bfe768c746080d6bf4d1206caa3d8cbd5af7 Mon Sep 17 00:00:00 2001
From: Igor Barcik <igor1606553@gmail.com>
Date: Wed, 9 Sep 2026 14:32:58 +0200
Subject: [PATCH] refactor(fx): give each FX slot independent DSP history
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Replace the single shared array of 9 effect units with a 2D array
of kNumFxSlots × kNumEffectTypes, so each slot owns its own DSP
state. This prevents state bleed when the same effect type appears
in multiple slots and allows reordering without carrying over
internal history.

Track activeTypes to skip unchanged slots. Remove the dry buffer
since it was unused.
---
 Source/FXProcessor.cpp | 27 +++++++++++++++------------
 Source/FXProcessor.h   |  8 +++++---
 2 files changed, 20 insertions(+), 15 deletions(-)

diff --git a/Source/FXProcessor.cpp b/Source/FXProcessor.cpp
index 72a296b..3e4e9a8 100644
--- a/Source/FXProcessor.cpp
+++ b/Source/FXProcessor.cpp
@@ -14,24 +14,27 @@ namespace serum
 
 FXProcessor::FXProcessor()
 {
-    units[0] = std::make_unique<HyperUnit>();
-    units[1] = std::make_unique<ChorusUnit>();
-    units[2] = std::make_unique<FlangerUnit>();
-    units[3] = std::make_unique<PhaserUnit>();
-    units[4] = std::make_unique<DistortionUnit>();
-    units[5] = std::make_unique<EQUnit>();
-    units[6] = std::make_unique<CompressorUnit>();
-    units[7] = std::make_unique<DelayUnit>();
-    units[8] = std::make_unique<ReverbUnit>();
+    for (auto& slotUnits : units)
+    {
+        slotUnits[0] = std::make_unique<HyperUnit>();
+        slotUnits[1] = std::make_unique<ChorusUnit>();
+        slotUnits[2] = std::make_unique<FlangerUnit>();
+        slotUnits[3] = std::make_unique<PhaserUnit>();
+        slotUnits[4] = std::make_unique<DistortionUnit>();
+        slotUnits[5] = std::make_unique<EQUnit>();
+        slotUnits[6] = std::make_unique<CompressorUnit>();
+        slotUnits[7] = std::make_unique<DelayUnit>();
+        slotUnits[8] = std::make_unique<ReverbUnit>();
+    }
 }
 
 FXProcessor::~FXProcessor() = default;
 
 void FXProcessor::prepare (double sampleRate, int maxBlockSize)
 {
-    for (auto& u : units)
-        u->prepare (sampleRate, maxBlockSize);
-    dry.setSize (2, maxBlockSize, false, false, true);
+    for (auto& slotUnits : units)
+        for (auto& u : slotUnits)
+            u->prepare (sampleRate, maxBlockSize);
     wet.setSize (2, maxBlockSize, false, false, true);
     reset();
 }
diff --git a/Source/FXProcessor.h b/Source/FXProcessor.h
index 9eb6876..bc3919a 100644
--- a/Source/FXProcessor.h
+++ b/Source/FXProcessor.h
@@ -31,7 +31,7 @@ struct FxSlotParams
 // ===========================================================================
 // Reorderable effects rack. Slots are processed in list order; reordering is
 // simply swapping FxSlotParams entries. Nine effect unit implementations are
-// owned here and shared across slots.
+// preconstructed per slot with independent DSP history.
 // ===========================================================================
 class FXProcessor
 {
@@ -47,8 +47,10 @@ public:
     static juce::String fxTypeName (int type);
 
 private:
-    std::array<std::unique_ptr<FXUnit>, 9> units;
-    juce::AudioBuffer<float> dry, wet;
+    static constexpr int kNumEffectTypes = (int) FxType::Count - 1;
+    std::array<std::array<std::unique_ptr<FXUnit>, kNumEffectTypes>, kNumFxSlots> units;
+    std::array<int, kNumFxSlots> activeTypes {};
+    juce::AudioBuffer<float> wet;
 };
 
 } // namespace serum