Function blendColor

pj_widgets/src/Timeline.cpp:275–278

Linear RGB blend a*(1-t) + b*t.

// Linear RGB blend a*(1-t) + b*t.
QColor blendColor(const QColor& a, const QColor& b, double t) {
  const auto mix = [t](float x, float y) { return static_cast<float>((x * (1.0 - t)) + (y * t)); };
  return QColor::fromRgbF(mix(a.redF(), b.redF()), mix(a.greenF(), b.greenF()), mix(a.blueF(), b.blueF()));
}

// Theme-derived timeline colours. The app syncs QPalette::Window / WindowText per
// theme (Theme::syncApplicationPalette) and QSS does NOT touch the palette, so a