ctrl- (several times to zoom)
./do_gantt.sh 
     12345678901234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234
T1   ▒         ▒         ▒         ▒         ▒         ▒         ▒         ▒         ▒         ▒         ▒         ▒         ▒         ▒         ▒         ▒         ▒         ▒         ▒         ▒         ▒         ▒         ▒         ▒         ▒         ▒         ▒         ▒         ▒         █
T2    ▒█                  ▒█                  ▒█                        ▒█            ▒█                  ▒█                  ▒█                  ▒█                        ▒█            ▒█                  ▒█                  ▒█                  ▒█                        ▒█            ▒█
T3                    ▒██                   ▒       ▒█                    ▒ ▒█                   ▒    ▒█                            ▒██                      ▒                ▒ ▒                    ▒    ▒█                  ▒██                           ▒██                      ▒    ▒█
T4      ▒███      ▒███      ▒███      ▒███      ▒███      ▒███      ▒███      ▒███      ▒███      ▒███      ▒███      ▒███      ▒███      ▒███      ▒███      ▒███      ▒███      ▒███      ▒███      ▒███      ▒███      ▒███      ▒███      ▒███      ▒███      ▒███      ▒███      ▒███      ▒███                                                         
T5          ▒██ ▒█                ▒ ▒█    ▒█                  ▒██ ▒█                ▒       ▒██ ▒               ▒██ ▒█                  ▒█    ▒██                 ▒██ ▒█                ▒       ▒██ ▒               ▒██ ▒█                ▒ ▒█    ▒█                  ▒██ ▒█                ▒       ▒██ █                                                    

ctrl+ (several times to unzoom)
