4cade/src/glue.launch.a

;license:MIT
;(c) 2018-9 by 4am
;
; Functions to launch games and self-running demos
;
; Public functions
; - GetGameToLaunch
; - GetGameInfo
; - GetGameInfoInActionSlideshow
; - PlayGame
; - Launch
;
; Public variables:
; - gGameToLaunch - 0-based index into gGamesListStore
;

GetGameToLaunch
; in:    gGameToLaunch = index into gGamesListStore
; out:   A/Y points to game filename
gGameToLaunch=*+1
         ldx   #$FF                  ; SMC
         +LDADDR gGamesListStore
         jmp   okvs_nth

GetGameInfo
; in:    A/Y points to game filename
; out:   C clear if game exists in gGamesListStore, and
;          A/Y points to game display name (but see hack notes below)
;          X = game index, or #$FF if the game doesn't really exist but
;          we want to return a successful result anyway (really, read the
;          hack notes, they're important)
;        C set if game does not exist (this can happen because slideshows
;          list games that require a joystick, but the games list parser
;          filters out joystick-only games if the machine doesn't have a
;          joystick)
         ldx   #$60
         +HIDE_NEXT_2_BYTES
GetGameInfoInActionSlideshow
         ldx   #$EA
         stx   @maybeExit
         +STAY @key
         +STAY @slideshowKey
         jsr   okvs_get
         !word gGamesListStore
@key     !word $FDFD                 ; SMC
         bcc   @exit
; Hack to allow self-running demos that don't correspond to a game
; filename. If the name ends in a '.', accept it unconditionally.
; The filename is its own display name. Launching this fake game
; will of course fail, so don't do that.
         +LDAY @key
         +STAY PARAM
         ldy   #0
         lda   (PARAM),y
         tay
         lda   (PARAM),y
         cmp   #"."
         beq   @forceGoodResult
         sec
@maybeExit
         !byte $00                   ; SMC
; if the key is still not found, AND the caller said to try this, then try
; getting the value of the current record from gSlideshowStore
; (some games have multiple action screenshots, in which case the filename of
; the action screenshot is not the game name, but the value is)
         jsr   okvs_get
         !word gSlideshowStore
@slideshowKey
         !word $FDFD                 ; SMC
         +STAY @key3
         jsr   okvs_get
         !word gGamesListStore
@key3    !word $FDFD                 ; SMC
; note that the game might still not be found (C will be set by okvs_get),
; which can happen if the game can't be played due to memory or joystick
; requirements
         rts
@forceGoodResult
         +LDAY @key
         ldx   #$FF
         clc
@exit    rts

PlayGame
         jsr   GetGameToLaunch
                                     ; A/Y = address of game filename
         +STAY SAVE
         +STAY @pfile                ; assume we're loading a game-specific prelaunch file

         jsr   Home                  ; clear screen (clobbers $106, must do now before loading prelaunch code)
         lda   #$20                  ; clear both hi-res pages
         sta   @clear+2              ; (in case game loader shows them, we don't want
         ldx   #$40                  ; to flash previous bits of the launcher UI)
         ldy   #$00
         tya
@clear   sta   $FD00,y               ; SMC
         iny
         bne   @clear
         inc   @clear+2
         dex
         bne   @clear

         jsr   LoadFile              ; load this game's prelaunch file at $106
         !word kPrelaunchDirectory
@pfile   !word $FDFD
         !word $0106

         ; we start by placing the subdirectory name at gPathname+kGameDirectoryLen
         ; to leave room for the GameDirectory name as the parent

         lda   #kGameDirectoryLen
         sta   gPathname
         +LDAY SAVE
         jsr   AddToPath

         ; attach the separator

         inc   gPathname
         lda   #'/'
         sta   gPathname+1,x

         ; then we save the length of the resulting string without the count byte

         dex
         txa
         pha

         ; then attach the game name

         +LDAY SAVE
         jsr   AddToPath

         ; don't look while I do this
         ; we "place" a string at gPathname+kGameDirectoryLen
         ; whose length is the subdirectory name and game name
         ; then we load it
         ; the load sets the path to the GameDirectory
         ; and then finds the subdirectory name and game name right after it
         ; and attaches it to the path by overwriting the count byte

         sec
         lda   gPathname
         sbc   #kGameDirectoryLen
         sta   gPathname+kGameDirectoryLen
         jsr   LoadFile              ; load the game startup file
         !word kGameDirectory
         !word gPathname+kGameDirectoryLen
         !word 0                     ; use file's default address

         pla
         sta   ProDOS_prefix         ; set 'root' directory to the path part
                                     ; of the game startup file we just loaded
                                     ; so games can load other files without
                                     ; knowing which directory they're in

         ; execution falls through here
Launch
         jsr   SwitchToBank2
         jmp   LaunchInternal