improved comment about m_pGLRenderer member in GLWaveformWidgetAbstract

src/waveform/widgets/glwaveformwidgetabstract.h

@@ -8,10 +8,12 @@
 
 QT_FORWARD_DECLARE_CLASS(QString)
 
-/// GLWaveformWidgetAbstract is a WaveformWidgetAbstract & WGLWidget. It may
-/// have a GLWaveformRenderer member which requires initialization that must be
-/// deferred until Qt calls WGLWidget::initializeGL and cannot be done in the
-/// constructor.
+/// GLWaveformWidgetAbstract is a WaveformWidgetAbstract & WGLWidget. Its optional
+/// member GLWaveformRenderer* m_pGlRenderer can implement a virtual method
+/// onInitializeGL, which will be called from GLWaveformRenderer::initializeGL
+/// (which overrides QGLWidget::initializeGL). This can be used for initialization
+/// that must be deferred until the GL context has been initialized and that can't
+/// be done in the constructor.
 class GLWaveformWidgetAbstract : public WaveformWidgetAbstract, public WGLWidget {
   public:
     GLWaveformWidgetAbstract(const QString& group, QWidget* parent)