76 lines
1.8 KiB
Plaintext
76 lines
1.8 KiB
Plaintext
( draw routines )
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:dev/r fff8 ( std read port )
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:dev/w fff9 ( std write port )
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;x_ 2 ;y_ 2 ;x0 2 ;y0 2 ;x1 2 ;y1 2 ;color 1
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;dx 2 ;dy 2 ;err 2 ;err2 2
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|0100 @RESET
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( set dev/write to screen )
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,01 ,dev/w STR
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,01 ,color STR
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+0030 ,x0 STR^ +0040 ,y0 STR^
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+0050 ,x1 STR^ +0060 ,y1 STR^
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,line JSR
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,02 ,color STR
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+0020 ,x0 STR^ +0010 ,y0 STR^
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+0060 ,x1 STR^ +0070 ,y1 STR^
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,line JSR
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( draw control points )
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,02 ,color STR
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,x0 LDR^ ,y0 LDR^ ,putpixel JSR
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,x1 LDR^ ,y1 LDR^ ,putpixel JSR
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,redraw JSR
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BRK
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@line
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,x0 LDR^ ,x_ STR^ ,y0 LDR^ ,y_ STR^ ( start at x0,y0 )
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,x1 LDR^ ,x0 LDR^ ,diff16sub JSR ,dx STR^ ( int dx = abs[x1 - x0] )
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,y1 LDR^ ,y0 LDR^ ,diff16sub JSR -0001 MUL!^ ,dy STR^ ( int dy = -abs[y1 - y0] )
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,dx LDR^ ,dy LDR^ ADD!^ ,err STR^ ( int err = dx + dy, e2; )
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@loop
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,x_ LDR^ ,y_ LDR^ ,putpixel JSR ( draw )
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,err LDR^ +0002 MUL!^ ,err2 STR^ ( e2 = 2 * err; )
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,err2 LDR^ ,dy LDR^ LTH!^ ,continue1 ROT JMP? POP^ ( e2 >= dy )
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,err LDR^ ,dy LDR^ ADD!^ ,err STR^ ( err += dy; )
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,x_ LDR^ +0001 ADD!^ ,x_ STR^ ( y0 += y0 < y1 ? 1 : -1; )
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@continue1
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,err2 LDR^ ,dx LDR^ GTH!^ ,continue2 ROT JMP? POP^ ( e2 <= dx )
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,err LDR^ ,dx LDR^ ADD!^ ,err STR^ ( err += dx; )
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,y_ LDR^ +0001 ADD!^ ,y_ STR^ ( y0 += y0 < y1 ? 1 : -1; )
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@continue2
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,x_ LDR^ ,x1 LDR^ LTH!^ ,loop ROT JMP? POP^ ( loop )
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RTS
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@redraw
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,0000 IOW^
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,0000 IOW^
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,00 IOW
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,01 IOW
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RTS
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@putpixel
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IOW^ ( y short )
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IOW^ ( x short )
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,color LDR IOW ( color byte )
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,00 IOW ( redraw byte )
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RTS
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@diff16
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OVR^ OVR^ GTH^ ,diff16sub ROT JMP? POP^
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SWP^ @diff16sub SUB^
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RTS
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|c000 @FRAME BRK
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|d000 @ERROR BRK
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|FFFA .RESET .FRAME .ERROR
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