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Routines |
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Used by the routine at DRAW_WALL_COLUMN.
A wall hides everything above it on the screen, so its colour runs from the attribute row holding its bottom line to the top of the play area: two attribute bytes a row, filled by COLOUR_STRIP in the attribute buffer (ATTR_BUFFER, 24 bytes a row, the bottom row first). The ink is bright green, cyan, yellow or white by the two low bits of the cell's type (CELL_TYPE); the paper is this turn's, LAST_FLASH, which a dying villain flashes. Nothing for a wall standing at or above line $B8.
The pair of bytes runs one past the end of a row when the column's x is in the last byte of the row: into the first byte of the next row, part of the two-byte margin at the left of the buffer that is never copied to the screen (COPY_ATTR_BUFFER shows 22 of each row's 24 bytes), and on the top row one past the attribute buffer altogether, into ATTR_SPILL. Measured: 28 of 752 fills in a random tour reached it, each at the right-hand edge; and over 877 calls the lowest wall bottom was line 126, so a fill never starts below the attribute buffer.
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| COLOUR_WALL | D356 | LD A,D | At or above line $BF: nothing | |||||||
| D357 | SUB $BF | |||||||||
| D359 | RET NC | |||||||||
| D35A | NEG | The attribute rows from its own up to the top: (191 - y) / 8; none, nothing | ||||||||
| D35C | SRL A | |||||||||
| D35E | SRL A | |||||||||
| D360 | SRL A | |||||||||
| D362 | RET Z | |||||||||
| D363 | LD B,A | B = the rows; HL = the attribute byte (ATTR_ADDRESS) | ||||||||
| D364 | EX DE,HL | |||||||||
| D365 | CALL ATTR_ADDRESS | |||||||||
| D368 | LD A,(CELL_TYPE) | Bright, with the ink from the cell type | ||||||||
| D36B | AND $03 | |||||||||
| D36D | OR $44 | |||||||||
| D36F | JP COLOUR_STRIP | Fill the rows, with this turn's paper (COLOUR_STRIP) | ||||||||
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