Routines
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97E1: Draw New Entity Row
Used by the routine at XORSpriteLoop.
Draws one row of the new sprite, using XOR, and moves up to the next row. It is a copy of DrawOldEntityRow that uses the jump at DrawNewEntityRow_Jump, which is changed by PrepDraw2.
Input
B Page of the shift table
DE Pointer to the pixel data
HL Screen address of the row
C Number of rows left
Output
C Number of rows left
DE Pointer to the next row of pixel data
HL Screen address of the next row
DrawNewEntityRow 97E1 LD A,C Copy the row count to A.
97E2 EX AF,AF' Store the row count in AF'.
97E3 LD A,(DE) Fetch the first byte of the row.
97E4 LD C,A Copy it to C to use as the index into the shift table.
97E5 PUSH HL Stash the screen address on the stack.
DrawNewEntityRow_Jump 97E6 JR DrawNewEntityRow_Jump Jump into the unrolled code. The operand of this instruction is changed by PrepDraw2.
DrawNewEntityRow_Byte_1 97E8 LD A,(DE) Byte 1 of the row: look up the shifted byte for the left cell and XOR it onto the screen.
97E9 LD C,A
97EA LD A,(BC)
97EB XOR (HL)
97EC LD (HL),A
97ED INC L
DrawNewEntityRow_Byte_1_Right 97EE INC B Look up the shifted byte for the cell to the right and XOR it onto the screen, then move on to the next byte of pixel data.
97EF LD A,(BC)
97F0 XOR (HL)
97F1 LD (HL),A
97F2 DEC B
97F3 INC DE
DrawNewEntityRow_Byte_2 97F4 LD A,(DE) Byte 2 of the row: look up the shifted byte for the left cell and XOR it onto the screen.
97F5 LD C,A
97F6 LD A,(BC)
97F7 XOR (HL)
97F8 LD (HL),A
97F9 INC L
DrawNewEntityRow_Byte_2_Right 97FA INC B Look up the shifted byte for the cell to the right and XOR it onto the screen, then move on to the next byte of pixel data.
97FB LD A,(BC)
97FC XOR (HL)
97FD LD (HL),A
97FE DEC B
97FF INC DE
DrawNewEntityRow_Byte_3 9800 LD A,(DE) Byte 3 of the row: look up the shifted byte for the left cell and XOR it onto the screen.
9801 LD C,A
9802 LD A,(BC)
9803 XOR (HL)
9804 LD (HL),A
9805 INC L
DrawNewEntityRow_Byte_3_Right 9806 INC B Look up the shifted byte for the cell to the right and XOR it onto the screen, then move on to the next byte of pixel data.
9807 LD A,(BC)
9808 XOR (HL)
9809 LD (HL),A
980A DEC B
980B INC DE
DrawNewEntityRow_Byte_4 980C LD A,(DE) Byte 4 of the row: look up the shifted byte for the left cell and XOR it onto the screen.
980D LD C,A
980E LD A,(BC)
980F XOR (HL)
9810 LD (HL),A
9811 INC L
DrawNewEntityRow_Byte_4_Right 9812 INC B Look up the shifted byte for the cell to the right and XOR it onto the screen, then move on to the next byte of pixel data.
9813 LD A,(BC)
9814 XOR (HL)
9815 LD (HL),A
9816 DEC B
9817 INC DE
DrawNewEntityRow_Byte_5 9818 LD A,(DE) Byte 5 of the row: look up the shifted byte for the left cell and XOR it onto the screen.
9819 LD C,A
981A LD A,(BC)
981B XOR (HL)
981C LD (HL),A
981D INC L
DrawNewEntityRow_Byte_5_Right 981E INC B Look up the shifted byte for the cell to the right and XOR it onto the screen, then move on to the next byte of pixel data.
981F LD A,(BC)
9820 XOR (HL)
9821 LD (HL),A
9822 DEC B
9823 INC DE
DrawNewEntityRow_Byte_6 9824 LD A,(DE) Byte 6 of the row: look up the shifted byte for the left cell and XOR it onto the screen.
9825 LD C,A
9826 LD A,(BC)
9827 XOR (HL)
9828 LD (HL),A
9829 INC L
DrawNewEntityRow_Byte_6_Right 982A INC B Look up the shifted byte for the cell to the right and XOR it onto the screen, then move on to the next byte of pixel data.
982B LD A,(BC)
982C XOR (HL)
982D LD (HL),A
982E DEC B
982F INC DE
DrawNewEntityRow_Byte_7 9830 LD A,(DE) Byte 7 of the row: look up the shifted byte for the left cell and XOR it onto the screen.
9831 LD C,A
9832 LD A,(BC)
9833 XOR (HL)
9834 LD (HL),A
9835 INC L
DrawNewEntityRow_Byte_7_Right 9836 INC B Look up the shifted byte for the cell to the right and XOR it onto the screen, then move on to the next byte of pixel data.
9837 LD A,(BC)
9838 XOR (HL)
9839 LD (HL),A
983A DEC B
983B INC DE
DrawNewEntityRow_Byte_8 983C LD A,(DE) Byte 8 of the row: look up the shifted byte for the left cell and XOR it onto the screen.
983D LD C,A
983E LD A,(BC)
983F XOR (HL)
9840 LD (HL),A
9841 INC L
DrawNewEntityRow_Byte_8_Right 9842 INC B Look up the shifted byte for the cell to the right and XOR it onto the screen, then move on to the next byte of pixel data.
9843 LD A,(BC)
9844 XOR (HL)
9845 LD (HL),A
9846 DEC B
9847 INC DE
DrawNewEntityRow_Byte_9 9848 LD A,(DE) Byte 9 of the row: look up the shifted byte for the left cell and XOR it onto the screen.
9849 LD C,A
984A LD A,(BC)
984B XOR (HL)
984C LD (HL),A
984D INC L
DrawNewEntityRow_Byte_9_Right 984E INC B Look up the shifted byte for the cell to the right and XOR it onto the screen, then move on to the next byte of pixel data.
984F LD A,(BC)
9850 XOR (HL)
9851 LD (HL),A
9852 DEC B
9853 INC DE
DrawNewEntityRow_Byte_9_Next 9854 EX AF,AF' Fetch the row count from AF'.
9855 LD C,A Copy the row count to C.
9856 POP HL Restore the screen address from the stack.
9857 DEC H Move up one pixel line.
9858 LD A,H Fetch the inverse of the high byte of the address in A.
9859 CPL
985A AND %00000111 Keep only the pixel line bits (bits 0-2).
985C RET NZ Return if the move up stayed inside the same character cell.
985D LD A,L Subtract 20 from the low byte to move up to the previous character row.
985E SUB $20
9860 LD L,A
9861 RET C Return if the move up stayed inside the same third of the screen.
9862 LD A,H Add 08 to the high byte to move up to the previous third of the screen.
9863 ADD A,$08
9865 LD H,A
9866 RET Return.
View the equivalent code in;
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