// ---------------------------------------------------------------------
        // jpanel: container for image editing function buttons
        // - gridbaglayout position: (1, 3)
        // - gridbaglayout dimensions: 1x1
        // - fills all available horizontal space
        
        cstMainConstraints.gridx = 1;
        cstMainConstraints.gridy = 3;
        
        cstMainConstraints.gridwidth = 1;
        cstMainConstraints.gridheight = 1;
        
        cstMainConstraints.weightx = 0.0;
        cstMainConstraints.weighty = 0.0;
        
        cstMainConstraints.fill = GridBagConstraints.HORIZONTAL;
        
        pnlMain.add(pnlFunctions);
        
        // =====================================================================