mirror of https://github.com/a2-4am/4cade.git
160 lines
4.8 KiB
Plaintext
160 lines
4.8 KiB
Plaintext
;License:MIT
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;(c) 2018-9 by 4am
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;
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; functions for managing which HGR page is showing, and doing things on the other one
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;
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; - GetOffscreenAddress
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; - LoadTitleOffscreen
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; - LoadCoverOffscreen
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; - LoadHelpOffscreen
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; - LoadGameTitleOffscreen
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; - ResyncPage
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; - ShowOtherPage
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; - ToggleOffscreenPage
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; - ClearOffscreen
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; - ClearHGR1
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; - ClearMem
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;
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; Public variables
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; - OffscreenPage
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;
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;------------------------------------------------------------------------------
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; GetOffscreenAddress
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; get high byte of HGR page that is currently not showing
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;
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; in: none
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; out: A = high byte of offscreen HGR page (#$20 or #$40)
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; preserves X/Y
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;------------------------------------------------------------------------------
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GetOffscreenAddress
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Ignore = * + 1 ; discard IRQs, particularly on the IIc
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lda #$40
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OffscreenPage = * + 1
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bne + ; SMC
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; 0 = currently showing HGR page 2
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; (so offscreen is page 1 @ $2000)
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; 1 = currently showing HGR page 1
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; (so offscreen is page 2 @ $4000)
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+ lsr
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rts
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;------------------------------------------------------------------------------
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; LoadTitleOffscreen
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; load title screen in the HGR page that is currently not showing
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;
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; in: none
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; out: all flags and registers clobbered
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;------------------------------------------------------------------------------
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LoadTitleOffscreen
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lda #<kTitleFile
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+HIDE_NEXT_2_BYTES
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;------------------------------------------------------------------------------
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; LoadHelpOffscreen
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; load help screen in the HGR page that is currently not showing
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;
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; in: none
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; out: all flags and registers clobbered
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;------------------------------------------------------------------------------
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LoadHelpOffscreen
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lda #<kHelpBackgroundFile
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+HIDE_NEXT_2_BYTES
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;------------------------------------------------------------------------------
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; LoadCoverOffscreen
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; load cover screen in the HGR page that is currently not showing
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;
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; in: none
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; out: all flags and registers clobbered
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;------------------------------------------------------------------------------
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LoadCoverOffscreen
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lda #<kCoverFile
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LoadOffscreenFromAY
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sta @fname
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jsr GetOffscreenAddress
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sta +
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jsr LoadFile
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!word kRootDirectory
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@fname !byte $FD ; SMC
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!byte >kCoverFile ; all of these are on the same page
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!byte $00
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+ !byte $FD ; SMC
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rts
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LoadGameTitleOffscreen
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; in: gGameToLaunch = index into gGamesListStore
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jsr GetGameToLaunch
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+STAY +
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jsr GetOffscreenAddress
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sta ++
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jsr LoadFile
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!word kHGRTitleDirectory
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+ !word $FDFD ; SMC
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!byte $00
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++ !byte $FD ; SMC
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rts
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;------------------------------------------------------------------------------
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; ClearOffscreen
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; clear $2000..$3FFF or $4000..$5FFF, depending on which HGR page is not
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; visible right now
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; does not change HGR mode
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;
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; in: none
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; out: $2000..$3FFF or $4000..$5FFF cleared
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; A = #$80
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; X = #$00
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; Y = #$00
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; Z = 1
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;------------------------------------------------------------------------------
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ClearOffscreen
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jsr GetOffscreenAddress
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+HIDE_NEXT_2_BYTES
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ClearHGR1
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lda #$20 ; note to self: LDX #$20 can't move here
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ldx #$20
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ClearMem
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sta @a+2
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lda #$80
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ldy #0
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@a sta $2000,y
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iny
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bne @a
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inc @a+2
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dex
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bne @a
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rts
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ResyncPage
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jsr ToggleOffscreenPage
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; /!\ execution falls through here to ShowOtherPage
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;------------------------------------------------------------------------------
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; ShowOtherPage
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; switch to the HGR page that is not currently showing
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;
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; in: none
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; out: A = new value of OffscreenPage
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; preserves X/Y
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;------------------------------------------------------------------------------
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ShowOtherPage
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jsr ToggleOffscreenPage
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bne +
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bit PAGE2 ; show page 2
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rts
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+ bit PAGE1 ; show page 1
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rts
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;------------------------------------------------------------------------------
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; ToggleOffscreenPage
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; switch the internal variable that tracks which HGR page is showing
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; (does not affect screen)
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;
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; in: none
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; out: A = new value of OffscreenPage
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; preserves X/Y
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;------------------------------------------------------------------------------
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ToggleOffscreenPage
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lda OffscreenPage
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eor #$01
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sta OffscreenPage
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rts
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