;Screen Control Assembly Lanuage Routines for C02

;Vic Display Colors
BLACK   EQU 0     Black
WHITE   EQU 1     White
RED     EQU 2     Red
CYAN    EQU 3     Cyan
MAGENT  EQU 4     Purple
GREEN   EQU 5     Green
BLUE    EQU 6     Blue
YELLOW  EQU 7     Yellow

;PETSCII Screen Control Characters
CHRCLR  EQU 147   Clear (CLR)
CHRDEL  EQU 20    Delete (DEL)
CHRDN   EQU 17    Cursor Down
CHRRTN  EQU 13    Return
CHRFN1  EQU 133   Function Key 1 (F1)
CHRFN2  EQU 137   Function Key 2 (F2)
CHRFN3  EQU 134   Function Key 3 (F3)
CHRFN4  EQU 138   Function Key 4 (F4)
CHRFN5  EQU 135   Function Key 5 (F5)
CHRFN6  EQU 139   Function Key 6 (F6)
CHRFN7  EQU 136   Function Key 7 (F7)
CHRFN8  EQU 140   Function Key 8 (F8)
CHRHOM  EQU 19    Home 
CHRINS  EQU 148   Insert
CHRLFT  EQU 157   Cursor Left
CHRRGT  EQU 29    Cursor Left
CHRRVF  EQU 146   Reverse Off
CHRRVN  EQU 18    Reverse On
CHRUP   EQU 145   Cursor Up

;PETSCII Box Drawing Characters
BOXBLC  EQU 173   Bottom Left Corner
BOXBRC  EQU 189   Bottom Right Corner
BOXBCT  EQU 177   Bottom to Cetter Tee 
BOXCTR  EQU 123   Center Cross
BOXHLN  EQU 96    Horizontal Line
BOXLCT  EQU 171   Left To Center T
BOXRCT  EQU 179   Right To Center T
BOXTLC  EQU 176   Top Left Corner
BOXTRC  EQU 174   Top Right Corner
BOXTCT  EQU 178   Top to Center T
BOXVLN  EQU 98    Verical Line

;PETSCII Color Code Table
CLRCDS  DC  144, 5, 28, 159, 156, 30, 32, 158

;Set Background Color
;Args: A = Vic Color Code
;Uses: TEMP0 - Temporary Storage
;Affects: A,C,N,Z
SCRBKG: LSR           ;Shift Color Code 4 Bits Left
        LSR 
        LSR 
        LSR 
        STA TEMP0     ;Save it
        LDA $900F     ;Read VIC Color Control Register
        AND #$15      ;Strip Existing Backround Color
        ORA           ;Add in Background Color
        STA $900F     ;Write back to VIC Chip
        RTS

;Set Text Color
;Args: A = Vic color code
;Affects: A,X,C,N,Z
SCRTXT: TAX           ;Transfer Color Code to Index
        LDA CLRTBL,X  ;Load PETSCII Color Control Character
        JMP PRCHR     ;Print Character and Return

;Clear Screen
;Affects A,C,N,Z
SCRCLR: LDA #CLEAR  ;Load Clear Screen Character
        JMP PRCHR   ;Print it and Return

;Move Cursor Down
;Affects A,C,N,Z
SCRDWN: LDA #DOWN   ;Load Cursor Down Character
        JMP PRCHR   ;Print it and Return

;Move Cursor To Home Position
;Affects A,C,N,Z
SRCHOM: LDA #HOME   ;Load Cursor Home Character
        JMP PRCHR   ;Print it and Return

;Move Cursor Left
;Affects A,C,N,Z
SCRLFT: LDA #LEFT   ;Load Cursor Left Character
        JMP PRCHR   ;Print it and Return

;Move Cursor Right
;Affects A,C,N,Z
SCRRGT: LDA #RIGHT  ;Load Cursor Left Character
        JMP PRCHR   ;Print it and Return

;Move Cursor Up
;Affects A,C,N,Z
SCRUP:  LDA #UP     ;Load Cursor Left Character
        JMP PRCHR   ;Print it and Return

;Move Cursor to Specified Coordinates
;Args: A = screen column (0 = top)   
;      Y = screen line (0 = left)
SCRMOV: TAX         ;Transfer Column to X Register
        CLC         ;Clear Carry Flag
        JMP $FFF0   ;Call PLOT Kernal Routine and Return

;Get Cursor Position
;Returns: A = current cursor column
;         Y = current cursor row
;         X = current cursor column
SCRPOS: SEC         ;Set Carry Flag
        JSR $FFF0   ;Call PLOT Kernal Routine
        TXA         ;Transfer Column to Accumulator
        RTS

;Get Screen Size
;Returns: A = width of screen in columns
;         Y = height of screen in rows
;         X = width of screen in columns
SCRSIZ: JSR $FFED   ;Call SCREEN Kernal Routine
        TXA         ;Transfer Width to Accumulator
        RTS