allshader RGB: Show a ghosted version of the original waveform behind…

src/waveform/renderers/allshader/waveformrendererrgb.cpp

@@ -26,6 +26,7 @@ void WaveformRendererRGB::onSetup(const QDomNode& node) {
 void WaveformRendererRGB::initializeGL() {
     WaveformRendererSignalBase::initializeGL();
     m_shader.init();
+    m_shader_ghost.init();
 }
 
 void WaveformRendererRGB::paintGL() {
@@ -94,6 +95,10 @@ void WaveformRendererRGB::paintGL() {
     m_vertices.reserve(reserved);
     m_colors.clear();
     m_colors.reserve(reserved);
+    m_vertices_ghost.clear();
+    m_vertices_ghost.reserve(reserved);
+    m_colors_ghost.clear();
+    m_colors_ghost.reserve(reserved);
 
     m_vertices.addRectangle(0.f,
             halfBreadth - 0.5f * devicePixelRatio,
@@ -140,21 +145,29 @@ void WaveformRendererRGB::paintGL() {
         float maxMid = static_cast<float>(u8maxMid);
         float maxHigh = static_cast<float>(u8maxHigh);
         float maxAllChn[2]{static_cast<float>(u8maxAllChn[0]), static_cast<float>(u8maxAllChn[1])};
+
+        float ghostLow = maxLow;
+        float ghostMid = maxMid;
+        float ghostHigh = maxHigh;
+        float maxAllChn_ghost[2]{static_cast<float>(u8maxAllChn[0]),
+                static_cast<float>(u8maxAllChn[1])};
         // Uncomment to undo scaling with pow(value, 2.0f * 0.316f) done in analyzerwaveform.h
         // float maxAllChn[2]{unscale(u8maxAllChn[0]), unscale(u8maxAllChn[1])};
 
         // Calculate the squared magnitude of the maxLow, maxMid and maxHigh values.
         // We take the square root to get the magnitude below.
         const float sum = math_pow2(maxLow) + math_pow2(maxMid) + math_pow2(maxHigh);
 
-        // Apply the gains
+        // Apply the gains (non-ghosted version only)
         maxLow *= lowGain;
         maxMid *= midGain;
         maxHigh *= highGain;
 
         // Calculate the squared magnitude of the gained maxLow, maxMid and maxHigh values
         // We take the square root to get the magnitude below.
         const float sumGained = math_pow2(maxLow) + math_pow2(maxMid) + math_pow2(maxHigh);
+        const float sumGained_ghost = math_pow2(ghostLow) +
+                math_pow2(ghostMid) + math_pow2(ghostHigh);
 
         // The maxAll values will be used to draw the amplitude. We scale them according to
         // magnitude of the gained maxLow, maxMid and maxHigh values
@@ -164,6 +177,10 @@ void WaveformRendererRGB::paintGL() {
             const float factor = std::sqrt(sumGained / sum);
             maxAllChn[0] *= factor;
             maxAllChn[1] *= factor;
+
+            const float factor_ghost = std::sqrt(sumGained_ghost / sum);
+            maxAllChn_ghost[0] *= factor_ghost;
+            maxAllChn_ghost[1] *= factor_ghost;
         }
 
         // Use the gained maxLow, maxMid and maxHigh values to calculate the color components
@@ -185,13 +202,35 @@ void WaveformRendererRGB::paintGL() {
             blue *= normFactor;
         }
 
+        float red_ghost = ghostLow * low_r + ghostMid * mid_r + ghostHigh * high_r;
+        float green_ghost = ghostLow * low_g + ghostMid * mid_g + ghostHigh * high_g;
+        float blue_ghost = ghostLow * low_b + ghostMid * mid_b + ghostHigh * high_b;
+        const float maxComponent_ghost = math_max3(red_ghost, green_ghost, blue_ghost);
+        if (maxComponent_ghost == 0.f) {
+            // Avoid division by 0
+            red_ghost = 0.f;
+            green_ghost = 0.f;
+            blue_ghost = 0.f;
+        } else {
+            const float normFactor_ghost = 1.f / maxComponent_ghost;
+            red_ghost *= normFactor_ghost;
+            green_ghost *= normFactor_ghost;
+            blue_ghost *= normFactor_ghost;
+        }
+
         // Lines are thin rectangles
         m_vertices.addRectangle(fpos - 0.5f,
                 halfBreadth - heightFactor * maxAllChn[0],
                 fpos + 0.5f,
                 halfBreadth + heightFactor * maxAllChn[1]);
         m_colors.addForRectangle(red, green, blue);
 
+        m_vertices_ghost.addRectangle(fpos - 0.5f,
+                halfBreadth - heightFactor * maxAllChn_ghost[0],
+                fpos + 0.5f,
+                halfBreadth + heightFactor * maxAllChn_ghost[1]);
+        m_colors_ghost.addForRectangle(red_ghost, green_ghost, blue_ghost, ghost_alpha);
+
         xVisualFrame += visualIncrementPerPixel;
     }
 
@@ -200,6 +239,28 @@ void WaveformRendererRGB::paintGL() {
 
     const QMatrix4x4 matrix = matrixForWidgetGeometry(m_waveformRenderer, true);
 
+    // Draw the ghost version first so the solid version is on top.
+    const int matrixLocation_ghost = m_shader_ghost.matrixLocation();
+    const int positionLocation_ghost = m_shader_ghost.positionLocation();
+    const int colorLocation_ghost = m_shader_ghost.colorLocation();
+
+    m_shader_ghost.bind();
+    m_shader_ghost.enableAttributeArray(positionLocation_ghost);
+    m_shader_ghost.enableAttributeArray(colorLocation_ghost);
+
+    m_shader_ghost.setUniformValue(matrixLocation_ghost, matrix);
+
+    m_shader_ghost.setAttributeArray(
+            positionLocation_ghost, GL_FLOAT, m_vertices_ghost.constData(), 2);
+    m_shader_ghost.setAttributeArray(
+            colorLocation_ghost, GL_FLOAT, m_colors_ghost.constData(), 4);
+
+    glDrawArrays(GL_TRIANGLES, 0, m_vertices_ghost.size());
+
+    m_shader_ghost.disableAttributeArray(positionLocation_ghost);
+    m_shader_ghost.disableAttributeArray(colorLocation_ghost);
+    m_shader_ghost.release();
+
     const int matrixLocation = m_shader.matrixLocation();
     const int positionLocation = m_shader.positionLocation();
     const int colorLocation = m_shader.colorLocation();

src/waveform/renderers/allshader/waveformrendererrgb.h

@@ -1,7 +1,9 @@
 #pragma once
 
+#include "shaders/rgbashader.h"
 #include "shaders/rgbshader.h"
 #include "util/class.h"
+#include "waveform/renderers/allshader/rgbadata.h"
 #include "waveform/renderers/allshader/rgbdata.h"
 #include "waveform/renderers/allshader/vertexdata.h"
 #include "waveform/renderers/allshader/waveformrenderersignalbase.h"
@@ -22,8 +24,13 @@ class allshader::WaveformRendererRGB final : public allshader::WaveformRendererS
 
   private:
     mixxx::RGBShader m_shader;
+    mixxx::RGBAShader m_shader_ghost;
     VertexData m_vertices;
     RGBData m_colors;
+    VertexData m_vertices_ghost;
+    RGBAData m_colors_ghost;
+
+    const float ghost_alpha = 0.25f;
 
     DISALLOW_COPY_AND_ASSIGN(WaveformRendererRGB);
 };