Fix live waveform scaling, drop GTK deps, and document the project

- Tune the live spectrum display to a fixed range matched to real per-FFT-bin
  levels (-40..0 dB) so typical content sits mid-screen instead of flying to
  the top or hugging the bottom; widen the SENS offset control to -48..+24 dB
- Disable JUCE_WEB_BROWSER so the WebKitGTK WebBrowserComponent (unused) is
  compiled out, letting the plugin build on Artix/Arch without GTK/WebKit dev
  headers
- Add a verbose README covering the bands, parameters, controls, structure,
  DSP, build steps, and the Linux/Artix note

Source/PluginEditor.cpp

@@ -298,7 +298,7 @@ GelykEQAudioProcessorEditor::GelykEQAudioProcessorEditor(GelykEQAudioProcessor&
         double min, max, def;
         const char* tip;
     } colorControls[] = {
-        { &waveSensLabel,  &waveSensSlider,  "SENS", -12.0, 12.0, 0.0, "Live waveform sensitivity (dB)" },
+        { &waveSensLabel,  &waveSensSlider,  "SENS", -48.0, 24.0, 0.0, "Live waveform sensitivity (dB offset)" },
         { &colorHueLabel, &colorHueSlider, "HUE", -0.5, 0.5, 0.0, "Master colour hue shift" },
         { &colorSatLabel, &colorSatSlider, "SAT", 0.0, 1.0, 1.0, "Master colour saturation" },
         { &colorBriLabel, &colorBriSlider, "BRI", 0.5, 1.5, 1.0, "Master colour brightness" },
@@ -801,21 +801,24 @@ void GelykEQAudioProcessorEditor::paint(juce::Graphics& g)
     g.setColour(lookAndFeel.cyan().withAlpha(0.55f));
     g.drawHorizontalLine((int) centreLineY, (float) mainArea.getX(), (float) mainArea.getRight());
 
-    // Spectrum overlay.
+    // Spectrum overlay. The live waveform uses a fixed range tuned to real
+    // per-FFT-bin levels: a single loud bin reads ~0 dB at the top edge, typical
+    // content (~-20 dB) sits mid-screen, and -40 dB is the floor. SENS shifts the
+    // whole trace up/down as a dB offset.
     if (spectrum.size() > 2)
     {
         const float waveAlpha = lookAndFeel.waveformOpacity;
-        const float sensFactor = std::pow(10.0f, lookAndFeel.waveSensitivity / 20.0f);
+        const float sensDb = lookAndFeel.waveSensitivity; // dB offset applied to the trace
+        const float dbMax = 0.0f;    // full-scale bin → top of the plot
+        const float dbMin = -40.0f;  // silence floor → bottom of the plot
         juce::Path path;
         const float x0 = (float) mainArea.getX();
         const float width = (float) mainArea.getWidth();
 
         for (int i = 0; i < spectrum.size(); ++i)
         {
-            float db = juce::Decibels::gainToDecibels(
-                juce::Decibels::decibelsToGain(spectrum[i]) * sensFactor);
-            db = juce::jlimit(-72.0f, 12.0f, db);
-            float norm = (db + 72.0f) / 84.0f; // 0..1 up
+            float db = juce::jlimit(dbMin, dbMax, spectrum[i] + sensDb);
+            float norm = (db - dbMin) / (dbMax - dbMin); // 0..1 up
             float xx = (i < freqBins.size())
                            ? bandFreqToX(freqBins[i], x0, width)
                            : x0 + (float) i / (float) (spectrum.size() - 1) * width;

Source/PluginEditor.h

@@ -35,7 +35,7 @@ public:
     float saturation = 1.0f;
     float brightness = 1.0f;
     float waveformOpacity = 0.2f;
-    float waveSensitivity = 0.0f; // in dB, added to the spectrum display level
+    float waveSensitivity = 0.0f; // in dB, vertical offset added to the live waveform trace
     float uiScale = 1.0f;
 
 private: