a                                            
                                                                                                                                                              
                                                                                                                                                              
                                                                                                                          OK, opacity min: that is transparent
                                                                                                                                                              
                                                                                                                                                              
                                                                                                                                                              
                                                                                                                 b                                            
                                                                                                                                                              
                                                                                                                                                              
                                                                                                                          KO, it's white not transparent!     
                                                                                                                                                              
                                                                                                                                                              
                                                                                                                                                              
                                                                                                                 c                                            
                                                                                                                                                              
                                                                                                                                                              
                                                      Observed on    : 1.2021.01beta3                                                                         
          (current version: 1.2024.5beta1)