Routines
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8460: Scroll the view when the player nears its edge
Used by the routine at DRAW_VIEW.
Reads where the player was placed this frame (the last entry of SPRITE_LIST) and, if that is outside a central window of the view, steps VIEW_ORIGIN a cell in the direction the player is facing -- unless the player is jumping or falling. It takes effect next frame, since the view has already been gathered.
SCROLL_VIEW 8460 LD DE,(PLAYER_SPRITE) Off the view altogether: leave it.
8464 LD A,D
8465 INC A
8466 RET Z
8467 DEC DE Undo the +1 PROJECT_SPRITES adds.
8468 LD A,E Across: inside if the column is 4-11 of 16...
8469 SUB $04
846B AND $0F
846D CP $08
846F JR NC,SCROLL_VIEW_0
8471 LD A,E ...and down: inside if the row is 8-23 of 32.
8472 RR D
8474 RRA
8475 RRA
8476 RRA
8477 RRA
8478 SUB $08
847A AND $1F
847C CP $10
847E RET C
SCROLL_VIEW_0 847F LD HL,(VIEW_ORIGIN) Outside: move the view.
8482 LD A,(PLAYER_FLAGS) Not while jumping or falling.
8485 BIT 1,A
8487 RET NZ
8488 LD A,(PLAYER_FALL)
848B AND A
848C RET NZ
848D LD A,(PLAYER_FACING) A cell the way the player faces.
8490 CALL STEP
8493 LD (VIEW_ORIGIN),HL
8496 RET
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