Apple-2gs-SW/iigs-game-engine
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Fix some linked-list manipulations

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This commit is contained in:
Lucas Scharenbroich 2023-03-08 16:29:12 -06:00
parent 029ab62f0c
commit 6c5e133b17
1 changed files with 10 additions and 18 deletions
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28
src/Sprite.s
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@ -438,7 +438,7 @@ _SortSprite
ldy _Sprites+SORTED_PREV,x
bmi :chk_fwd
cmp _Sprites+SPRITE_CLIP_TOP,y
bcc :chk_bkwd ; The current node needs to move to an lower position
bcc :scan_bkwd ; The current node needs to move to an lower position
:chk_fwd
ldy _Sprites+SORTED_NEXT,x ; If there is nothing ahead of the current node, we're done
@ -502,12 +502,6 @@ _SortSprite
sta _Sprites+SORTED_NEXT,y
rts
:chk_bkwd
ldy _Sprites+SORTED_PREV,x ; If there is nothing behind the current node, we're done
bmi :done
cmp _Sprites+SPRITE_CLIP_TOP,y ; If the current node is >= the previous node, we're done
bcs :done
; Look to move the sprite into an earlier position
:scan_bkwd
lda _Sprites+SORTED_PREV,y ; Need to step backward; if we're at the beginning, then insert here
@ -529,16 +523,16 @@ _SortSprite
jsr _OrphanNode
tya
sta _Sprites+SORTED_NEXT,x ; Link X to Y
sta _Sprites+SORTED_PREV,x ; c <=> y <-- x --- d
lda _Sprites+SORTED_PREV,y
sta _Sprites+SORTED_PREV,x ; Link X to C
lda _Sprites+SORTED_NEXT,y ; c <=> y <-- x --> d
sta _Sprites+SORTED_NEXT,x
txa ; Link Y to X
sta _Sprites+SORTED_PREV,y
txa
ldx _Sprites+SORTED_NEXT,y
sta _Sprites+SORTED_NEXT,y ; c <=> y <=> x --> d
ldy _Sprites+SORTED_PREV,x ; Link C to X
sta _Sprites+SORTED_NEXT,y
sta _Sprites+SORTED_PREV,x ; c <=> y <=> x <=> d
rts
; Move X to the front of the list. Y points to the first element
@ -559,7 +553,6 @@ _SortSprite
sta _Sprites+SORTED_PREV,x
tya
sta _Sprites+SORTED_NEXT,x
rts
:done
rts
@ -596,7 +589,6 @@ _InsertSprite
cmp _Sprites+SPRITE_CLIP_TOP,y
bcs :next
:insert
lda _Sprites+SORTED_PREV,y
sta _Sprites+SORTED_PREV,x ; [p] <-- [c] [n]
@ -604,10 +596,10 @@ _InsertSprite
sta _Sprites+SORTED_NEXT,x ; [p] <-- [c] --> [n]
txa
ldx _Sprites+SORTED_PREV,y ; get ref to the [p]revious node
sta _Sprites+SORTED_PREV,y ; [p] <-- [c] <=> [n]
ldy _Sprites+SORTED_PREV,x
sta _Sprites+SORTED_NEXT,y ; [p] <=> [c] <=> [n]
sta _Sprites+SORTED_NEXT,x ; [p] <=> [c] <=> [n]
rts