C02/include/vic20/screen.a02

;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
MAGNTA  EQU 4     Purple
GREEN   EQU 5     Green
BLUE    EQU 6     Blue
YELLOW  EQU 7     Yellow

;PETSCII Color Codes
CTLBLK  EQU 144   Black
CTLWHT  EQU 5     White
CTLRED  EQU 28    Red
CTLCYN  EQU 159   Cyan
CTLPUR  EQU 156   Purple
CTLGRN  EQU 30    Green
CTLBLU  EQU 32    Blue
CTLYLW  EQU 158   Yellow

;PETSCII Screen Control Codes
CLEAR   EQU 147   Clear (CLR)
DELETE  EQU 20    Delete (DEL)
DOWN    EQU 17    Cursor Down
ENTER   EQU 13    Return
FN1     EQU 133   Function Key 1 (F1)
FN2     EQU 137   Function Key 2 (F2)
FN3     EQU 134   Function Key 3 (F3)
FN4     EQU 138   Function Key 4 (F4)
FN5     EQU 135   Function Key 5 (F5)
FN6     EQU 139   Function Key 6 (F6)
FN7     EQU 136   Function Key 7 (F7)
FN8     EQU 140   Function Key 8 (F8)
HOME    EQU 19    Home 
INSERT  EQU 148   Insert
LEFT    EQU 157   Cursor Left
RIGHT   EQU 29    Cursor Left
RVSOFF  EQU 146   Reverse Off
RVSON   EQU 18    Reverse On
UP      EQU 145   Cursor Up

;PETSCII Box Drawing Characters
BTMLFT  EQU 173   Bottom Left Corner
BTMRGT  EQU 189   Bottom Right Corner
BTMTEE  EQU 177   Bottom to Cetter Tee 
CTRCRS  EQU 123   Center Cross
HRZLIN  EQU 96    Horizontal Line
LFTTEE  EQU 171   Left To Center T
RGHTEE  EQU 179   Right To Center T
TOPLFT  EQU 176   Top Left Corner
TOPRGT  EQU 174   Top Right Corner
TOPTEE  EQU 178   Top to Center T
VRTLIN  EQU 98    Verical Line

;PETSII Color Table
CLRTBL: DB CTLBLK,CTLWHT,CTLRED,CTLCYN,CTLPUR,CTLGRN,CTLBLU,CTLYLW

;Set Background Color
;Args: A = Vic Color Code
;Uses: TEMP0 - Temporary Storage
;Affects: A,C,N,Z
BKGCLR: 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
TXTCLR: 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
CLRSCN: LDA #CLEAR  ;Load Clear Screen Character
        JMP PRCHR   ;Print it and Return

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

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

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

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

;Move Cursor Up
;Affects A,C,N,Z
CRSRUP: 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)
MVCRSR: TAX         ;Transfer Column to X Register
        CLC         ;Clear Carry Flag
        JMP $FFF0   ;Call PLOT Kernal Routine and Return

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

;Get Screen Height in Rows
;Returns: A = height of screen in rows
;         Y = height of screen in rows
;         X = width of screen in columns
SCNGHT: JSR $FFED   ;Call SCREEN Kernal Routine
        TYA         ;Transfer Height to Accumulator
        RTS

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

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