changelog
    
    
    - Wed, 30 May 2018 22:31:06 +0300
 
    - by Teemu Piippo <teemu@hecknology.net> [Wed, 30 May 2018 22:31:06 +0300] rev 1390
 
    - added draw plane feature (doesn't work with circle draw quite right yet)
 
    - Sat, 26 May 2018 17:28:15 +0300
 
    - by Teemu Piippo <teemu@hecknology.net> [Sat, 26 May 2018 17:28:15 +0300] rev 1389
 
    - refactored signal blocking
 
    - Thu, 10 May 2018 15:54:26 +0300
 
    - by Teemu Piippo <teemu@hecknology.net> [Thu, 10 May 2018 15:54:26 +0300] rev 1388
 
    - fixed that scaling factors could be negative