4cade/src/ui.offscreen.a
2019-10-09 21:26:18 -07:00

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;License:MIT
;(c) 2018-9 by 4am
;
; functions for managing which HGR page is showing, and doing things on the other one
;
; - GetOffscreenAddress
; - LoadTitleOffscreen
; - LoadCoverOffscreen
; - LoadHelpOffscreen
; - LoadGameTitleOffscreen
; - ResyncPage
; - ShowOtherPage
; - ToggleOffscreenPage
; - ClearOffscreen
; - ClearHGR1
; - ClearMem
;
; Public variables
; - OffscreenPage
;
;------------------------------------------------------------------------------
; GetOffscreenAddress
; get high byte of HGR page that is currently not showing
;
; in: none
; out: A = high byte of offscreen HGR page (#$20 or #$40)
; preserves X/Y
;------------------------------------------------------------------------------
GetOffscreenAddress
lda #$40
OffscreenPage = * + 1
bne + ; SMC
; 0 = currently showing HGR page 2
; (so offscreen is page 1 @ $2000)
; 1 = currently showing HGR page 1
; (so offscreen is page 2 @ $4000)
+ lsr
rts
;------------------------------------------------------------------------------
; LoadTitleOffscreen
; load title screen in the HGR page that is currently not showing
;
; in: none
; out: all flags and registers clobbered
;------------------------------------------------------------------------------
LoadTitleOffscreen
lda #<kTitleFile
+HIDE_NEXT_2_BYTES
;------------------------------------------------------------------------------
; LoadHelpOffscreen
; load help screen in the HGR page that is currently not showing
;
; in: none
; out: all flags and registers clobbered
;------------------------------------------------------------------------------
LoadHelpOffscreen
lda #<kHelpFile
+HIDE_NEXT_2_BYTES
;------------------------------------------------------------------------------
; LoadCoverOffscreen
; load cover screen in the HGR page that is currently not showing
;
; in: none
; out: all flags and registers clobbered
;------------------------------------------------------------------------------
LoadCoverOffscreen
lda #<kCoverFile
LoadOffscreenFromAY
sta @fname
jsr GetOffscreenAddress
sta +
jsr LoadFile
!word kRootDirectory
@fname !byte $FD ; SMC
!byte >kCoverFile ; all of these are on the same page
!byte $00
+ !byte $FD ; SMC
rts
LoadGameTitleOffscreen
; in: gGameToLaunch = index into gGamesListStore
jsr GetGameToLaunch
+STAY +
jsr GetOffscreenAddress
sta ++
jsr LoadFile
!word kHGRTitleDirectory
+ !word $FDFD ; SMC
!byte $00
++ !byte $FD ; SMC
rts
;------------------------------------------------------------------------------
; ClearOffscreen
; clear $2000..$3FFF or $4000..$5FFF, depending on which HGR page is not
; visible right now
; does not change HGR mode
;
; in: none
; out: $2000..$3FFF or $4000..$5FFF cleared
; A = #$80
; X = #$00
; Y = #$00
; Z = 1
;------------------------------------------------------------------------------
ClearOffscreen
jsr GetOffscreenAddress
+HIDE_NEXT_2_BYTES
ClearHGR1
lda #$20 ; note to self: LDX #$20 can't move here
ldx #$20
ClearMem
sta @a+2
lda #$80
ldy #0
@a sta $2000,y
iny
bne @a
inc @a+2
dex
bne @a
rts
ResyncPage
jsr ToggleOffscreenPage
; /!\ execution falls through here to ShowOtherPage
;------------------------------------------------------------------------------
; ShowOtherPage
; switch to the HGR page that is not currently showing
;
; in: none
; out: A = new value of OffscreenPage
; preserves X/Y
;------------------------------------------------------------------------------
ShowOtherPage
jsr ToggleOffscreenPage
bne +
bit PAGE2 ; show page 2
rts
+ bit PAGE1 ; show page 1
rts
;------------------------------------------------------------------------------
; ToggleOffscreenPage
; switch the internal variable that tracks which HGR page is showing
; (does not affect screen)
;
; in: none
; out: A = new value of OffscreenPage
; preserves X/Y
;------------------------------------------------------------------------------
ToggleOffscreenPage
lda OffscreenPage
eor #$01
sta OffscreenPage
rts