ref: 174ef99e0e0caf5e8af2825d0034c9f7b72784f8
dir: /engine/menus/swap_items.asm/
HandleItemListSwapping:: ld a, [wListMenuID] cp ITEMLISTMENU jp nz, DisplayListMenuIDLoop ; only rearrange item list menus push hl ld hl, wListPointer ld a, [hli] ld h, [hl] ld l, a inc hl ; hl = beginning of list entries ld a, [wCurrentMenuItem] ld b, a ld a, [wListScrollOffset] add b add a ld c, a ld b, 0 add hl, bc ; hl = address of currently selected item entry ld a, [hl] pop hl inc a jp z, DisplayListMenuIDLoop ; ignore attempts to swap the Cancel menu item ld a, [wMenuItemToSwap] ; ID of item chosen for swapping (counts from 1) and a ; has the first item to swap already been chosen? jr nz, .swapItems ; if not, set the currently selected item as the first item ld a, [wCurrentMenuItem] inc a ld b, a ld a, [wListScrollOffset] ; index of top (visible) menu item within the list add b ld [wMenuItemToSwap], a ; ID of item chosen for swapping (counts from 1) ld c, 20 call DelayFrames jp DisplayListMenuIDLoop .swapItems ld a, [wCurrentMenuItem] inc a ld b, a ld a, [wListScrollOffset] add b ld b, a ld a, [wMenuItemToSwap] ; ID of item chosen for swapping (counts from 1) cp b ; is the currently selected item the same as the first item to swap? jp z, DisplayListMenuIDLoop ; ignore attempts to swap an item with itself dec a ld [wMenuItemToSwap], a ; ID of item chosen for swapping (counts from 1) ld c, 20 call DelayFrames push hl push de ld hl, wListPointer ld a, [hli] ld h, [hl] ld l, a inc hl ; hl = beginning of list entries ld d, h ld e, l ; de = beginning of list entries ld a, [wCurrentMenuItem] ld b, a ld a, [wListScrollOffset] add b add a ld c, a ld b, 0 add hl, bc ; hl = address of currently selected item entry ld a, [wMenuItemToSwap] ; ID of item chosen for swapping (counts from 1) add a add e ld e, a jr nc, .noCarry inc d .noCarry ; de = address of first item to swap ld a, [de] ld b, a ld a, [hli] cp b jr z, .swapSameItemType .swapDifferentItems ldh [hSwapItemID], a ; save second item ID ld a, [hld] ldh [hSwapItemQuantity], a ; save second item quantity ld a, [de] ld [hli], a ; put first item ID in second item slot inc de ld a, [de] ld [hl], a ; put first item quantity in second item slot ldh a, [hSwapItemQuantity] ld [de], a ; put second item quantity in first item slot dec de ldh a, [hSwapItemID] ld [de], a ; put second item ID in first item slot xor a ld [wMenuItemToSwap], a ; 0 means no item is currently being swapped pop de pop hl jp DisplayListMenuIDLoop .swapSameItemType inc de ld a, [hl] ld b, a ld a, [de] add b ; a = sum of both item quantities cp 100 ; is the sum too big for one item slot? jr c, .combineItemSlots ; swap enough items from the first slot to max out the second slot if they can't be combined sub 99 ld [de], a ld a, 99 ld [hl], a jr .done .combineItemSlots ld [hl], a ; put the sum in the second item slot ld hl, wListPointer ld a, [hli] ld h, [hl] ld l, a dec [hl] ; decrease the number of items ld a, [hl] ld [wListCount], a ; update number of items variable cp 1 jr nz, .skipSettingMaxMenuItemID ld [wMaxMenuItem], a ; if the number of items is only one now, update the max menu item ID .skipSettingMaxMenuItemID dec de ld h, d ld l, e inc hl inc hl ; hl = address of item after first item to swap .moveItemsUpLoop ; erase the first item slot and move up all the following item slots to fill the gap ld a, [hli] ld [de], a inc de inc a ; reached the $ff terminator? jr z, .afterMovingItemsUp ld a, [hli] ld [de], a inc de jr .moveItemsUpLoop .afterMovingItemsUp xor a ld [wListScrollOffset], a ld [wCurrentMenuItem], a .done xor a ld [wMenuItemToSwap], a ; 0 means no item is currently being swapped pop de pop hl jp DisplayListMenuIDLoop