alien: Routine at 35451

35451: SwapHeldItems

Action on the back-item row (9): swap the actor's front and back hands — exchange HeldItemFront/HeldItemBack, flip the two markers in ItemLocations (29940) by +/-32, adjust the sprite position by the difference of the two courage bonuses, and redraw the front item's name.
35451	CALL 31820	refresh HeldItemFront/Back for this actor
35454	LD (IX+0),0
35458	LD DE,(31248)	E = front item, D = back item
35462	LD HL,29984	ItemCourageBonus:
35465	PUSH HL
35466	LD C,E
35467	LD B,0
35469	ADD HL,BC
35470	LD E,(HL)	E = bonus[front]
35471	LD C,D
35472	POP HL
35473	ADD HL,BC
35474	LD D,(HL)	D = bonus[back]
35475	LD A,(IX+5)	courage += bonus[back] - bonus[front]
35478	SUB E
35479	ADD A,D
35480	CP 127	(clamp underflow to 0)
35482	JR C,35485
35484	XOR A
35485	LD (IX+5),A
35488	LD A,(IX+6)	morale likewise
35491	SUB E
35492	ADD A,D
35493	CP 127
35495	JR C,35498
35497	XOR A
35498	LD (IX+6),A
35501	LD BC,(31248)	C = front item, B = back item
35505	LD L,B	swap HeldItemFront <-> HeldItemBack
35506	LD H,C
35507	LD (31248),HL
35510	LD HL,29940	ItemLocations:
35513	PUSH HL
35514	LD E,C	old front item's marker -32
35515	LD D,0	(160+slot -> 128+slot: now in the back hand)
35517	ADD HL,DE
35518	LD A,(HL)
35519	SUB 32
35521	LD (HL),A
35522	POP HL
35523	LD E,B	old back item's marker +32
35524	ADD HL,DE	(128+slot -> 160+slot: now in front)
35525	LD A,(HL)
35526	ADD A,32
35528	LD (HL),A
35529	LD HL,18486	redraw the " use:" rows:
35532	LD (31257),HL
35535	LD A,(31248)
35538	CALL 31857
35541	CALL 31634	draw the new front item's name
35544	LD A,(31249)
35547	CALL 31857	and the new back item's name
35550	CALL 31634
35553	CALL 32385
35556	CALL 36793
35559	RET