VolksForth/st/DRAGON1.FB

\\ documentation for dargon demo                    tcas20130106start the dragon with : <pos int> DRAG                                        or with : <1 or -1> <pos int> DRAGON                                                                              DRAG clears the screen, defines the starting point and executes DRAGON.                                                         The variable STEPSIZE defines the size of steps between 1 and 3 (larger values will produce grabage)                                                                                            odd numbers as input values do not work                                                                                         DDEMO is a loop executing the DRAGON demo which can be stopped  with a keypress once the 2nd dragon is fully painted (it is     recommended to press a key a little in advance)                                                                                                                                                 \ dragon-loadscreen                                  cas20130106                                                                Onlyforth                                                                                                                       \needs Graphics    include line_a.fb                                                                                            Onlyforth    GEM also    Graphics also                                                                                          decimal                                                                                                                         1 5 +thru                                                                                                                                                                                                                                                                                                                                                                                       \ dragon s.2                                           03oct86we                                                                Variable angle                                                  Variable stepsize      1 stepsize !                             Variable color         1 color !                                Variable xcood         Variable ycood                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                           \ set_pixel                                            03oct86we                                                                Label ?step                                                        stepsize pcrel) D2 move  D1 tst  0<> IF  D2 neg  THEN  rts                                                                   Code set_pixel                                                     xcood pcrel) D3 move   ycood pcrel) D4 move                     angle pcrel) D0 move   1 # D0 asr   D0 D1 move   1 D0 andi      1 # D1 asr   1 D1 andi                                          D0 tst  0=  IF ?step bsr  D2 D3 add   D3 xcood R#) move THEN    D0 tst  0<> IF ?step bsr  D2 D4 add   D4 ycood R#) move THEN    D3 SP -) move   D4 SP -) move   color pcrel) SP -) move         ;c: put_pixel ;