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Routines |
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Handler for the object type 17 which is the rope that hangs from the ceiling of a room (see Set_Up_Rope). It is the handler of record 3 while Sabreman is not holding the rope; when he grabs it the record is cleared and Handle_Sabreman_On_Rope takes over.
Each call lengthens the rope by one (the length is the word at Rope_Length) until its low seven bits reach 38 and sets bit 0 of the redraw flags so that the rope gets drawn.
If the rope is swinging (the displacement in Rope_Displacement_Pixels is not zero) the displacement moves back towards zero by 02 on each call and the counter in byte 06 of the record is set to 03. When the rope hangs straight down, the counter counts down to zero and the redraw flag is set for each count. Finally the position of the end of the rope is worked out (Position_Rope_End) and the rope is drawn (Draw_Rope).
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Make the rope longer, up to a length of 38.
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| Handle_Rope | AA4C | LD HL,($AAA5) | Fetch the length of the rope from Rope_Length. | |||||
| AA4F | LD A,L | Copy the low byte to A. | ||||||
| AA50 | AND $7F | Keep only the low seven bits. | ||||||
| AA52 | CP $38 | Jump to Handle_Rope_Fetch_Displacement if the rope is already full length (the length is 38 or more). | ||||||
| AA54 | JR NC,Handle_Rope_Fetch_Displacement | |||||||
| AA56 | INC HL | Add one to the length, so that the rope grows. | ||||||
| AA57 | LD ($AAA5),HL | Store the new length of the rope. | ||||||
| AA5A | SET 0,(IX+$0F) | Set bit 0 of the redraw flags, so that the rope is drawn. | ||||||
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Make the swing die down.
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| Handle_Rope_Fetch_Displacement | AA5E | LD A,($AAA4) | Fetch the displacement of the end of the rope. | |||||
| AA61 | AND A | Jump to Handle_Rope_Store_Displacement if the rope hangs straight down. | ||||||
| AA62 | JR Z,Handle_Rope_Store_Displacement | |||||||
| AA64 | LD (IX+$06),$03 | Set the swing counter to 03. | ||||||
| AA68 | JP P,Handle_Rope_Reduce_Positive | Jump to Handle_Rope_Reduce_Positive if the end of the rope is displaced to the right (the displacement is positive). | ||||||
| AA6B | INC A | Add two to the displacement, which moves it back towards zero. | ||||||
| AA6C | INC A | |||||||
| AA6D | JP P,Handle_Rope_Zero_Displacement | Jump to Handle_Rope_Zero_Displacement if the displacement has become zero or positive. | ||||||
| Handle_Rope_Store_Displacement | AA70 | LD ($AAA4),A | Store the displacement of the end of the rope. | |||||
| AA73 | LD A,(IX+$06) | Fetch the swing counter. | ||||||
| AA76 | AND A | Jump to Handle_Rope_Position_End if the swing counter is zero. | ||||||
| AA77 | JR Z,Handle_Rope_Position_End | |||||||
| AA79 | DEC (IX+$06) | Decrease the swing counter. | ||||||
| AA7C | SET 0,(IX+$0F) | Set bit 0 of the redraw flags, so that the rope is drawn. | ||||||
| Handle_Rope_Position_End | AA80 | CALL Position_Rope_End | Work out the position of the end of the rope. | |||||
| AA83 | JP Draw_Rope | Jump to Draw_Rope to draw the rope. | ||||||
| Handle_Rope_Zero_Displacement | AA86 | XOR A | Set the displacement to zero, so that the rope hangs straight down. | |||||
| AA87 | LD ($AAA4),A | |||||||
| AA8A | JR Handle_Rope_Store_Displacement | Jump to Handle_Rope_Store_Displacement. | ||||||
| Handle_Rope_Reduce_Positive | AA8C | DEC A | Subtract two from the displacement, which moves it back towards zero. | |||||
| AA8D | DEC A | |||||||
| AA8E | JP M,Handle_Rope_Zero_Displacement | Jump to Handle_Rope_Zero_Displacement if the displacement has become negative. | ||||||
| AA91 | JR Handle_Rope_Store_Displacement | Jump to Handle_Rope_Store_Displacement. | ||||||
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