Sabre Wulf: Routine at B187

B187: Enter Room Left

Used by the routine at MoveActorLeft.

Used by MoveActor when an actor has gone off the left of the screen. The actor is put at the right of the room to the left (the room number is one less, but the room stays in the same row of the map) and its X position is set so that its right edge is at the edge of the screen.

Input
IX	Actor record

Output
E	New X position

EnterRoomLeft

B187

LD A,($96AD)

Fetch the width of the actor from Actor_Width.

B18A

NEG

Negate the width.

B18C

DEC A

Subtract one.

B18D

LD E,A

Stash the new X position in E.

B18E

LD A,(IX+$01)

Fetch the room of the actor.

B191

LD C,A

Stash the room in C.

B192

DEC A

Move to the room on the left.

This entry point is used by the routine at EnterRoomRight.

EnterRoomLeft_Row

B193

AND %00001111

Keep only bits 0-3 (the column).

B195

LD B,A

Stash the column in B.

B196

LD A,C

Fetch the old room.

B197

AND %11110000

Keep only bits 4-7 (the row).

B199

OR B

Merge in the new column.

B19A

LD (IX+$01),A

Set the new room of the actor.

B19D

JR EnterRoom

Jump to EnterRoom.