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agon_graphics.asm
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agon_graphics.asm
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;
; Title: BBC Basic for AGON - Graphics stuff
; Author: Dean Belfield
; Created: 07/08/2022
; Last Updated: 19/05/2023
;
; Modinfo:
; 19/08/2022: Added GETSCHR, POINT
; 15/02/2023: Fixed COLOUR, GCOL
; 23/02/2023: Fixed MODE
; 04/03/2023: Updated POINT to return colour index, not RGB
; 12/03/2023: Palette change now supports COLOUR l, p syntax
; 21/03/2023: Now uses vdp defines
; 19/05/2023: Refactored GETSCHR for OSBYTE_87
.ASSUME ADL = 0
INCLUDE "equs.inc"
INCLUDE "macros.inc"
INCLUDE "mos_api.inc" ; In MOS/src
SEGMENT CODE
XDEF CLG
XDEF CLRSCN
XDEF MODE
XDEF COLOUR
XDEF GCOL
XDEF MOVE
XDEF PLOT
XDEF DRAW
XDEF POINT
XDEF GETSCHR
XDEF GETSCHR_1
XREF OSWRCH
XREF ASC_TO_NUMBER
XREF EXTERR
XREF EXPRI
XREF COMMA
XREF XEQ
XREF NXT
XREF BRAKET
XREF COUNT0
XREF CRTONULL
XREF NULLTOCR
XREF CRLF
XREF EXPR_W2
XREF INKEY1
; CLG: clears the graphics area
;
CLG: VDU 10h
JP XEQ
; CLS: clears the text area
;
CLRSCN: LD A, 0Ch
JP OSWRCH
; MODE n: Set video mode
;
MODE: PUSH IX ; Get the system vars in IX
MOSCALL mos_sysvars ; Reset the semaphore
RES.LIL 4, (IX+sysvar_vpd_pflags)
CALL EXPRI
EXX
VDU 16H ; Mode change
VDU L
MOSCALL mos_sysvars
$$: BIT.LIL 4, (IX+sysvar_vpd_pflags)
JR Z, $B ; Wait for the result
POP IX
JP XEQ
; GET(x,y): Get the ASCII code of a character on screen
;
GETSCHR: INC IY
CALL EXPRI ; Get X coordinate
EXX
PUSH HL ; Stack X
CALL COMMA
CALL EXPRI ; Get Y coordinate
EXX
CALL BRAKET ; Closing bracket
POP DE ; Pop X back into DE
CALL GETSCHR_1
JP INKEY1
;
; Fetch a character from the screen
; - DE: X coordinate
; - HL: Y coordinate
; Returns
; - A: The character or FFh if no match
; - F: C if match, otherwise NC
;
GETSCHR_1: PUSH IX ; Get the system vars in IX
MOSCALL mos_sysvars ; Reset the semaphore
RES.LIL 1, (IX+sysvar_vpd_pflags)
VDU 23
VDU 0
VDU vdp_scrchar
VDU E
VDU D
VDU L
VDU H
$$: BIT.LIL 1, (IX+sysvar_vpd_pflags)
JR Z, $B ; Wait for the result
LD.LIL A, (IX+sysvar_scrchar) ; Fetch the result in A
OR A ; Check for 00h
SCF ; C = character map
JR NZ, $F ; We have a character, so skip next bit
XOR A ; Clear carry
$$: POP IX
RET
; POINT(x,y): Get the pixel colour of a point on screen
;
POINT: CALL EXPRI ; Get X coordinate
EXX
LD (VDU_BUFFER+0), HL
CALL COMMA
CALL EXPRI ; Get Y coordinate
EXX
LD (VDU_BUFFER+2), HL
CALL BRAKET ; Closing bracket
;
PUSH IX ; Get the system vars in IX
MOSCALL mos_sysvars ; Reset the semaphore
RES.LIL 2, (IX+sysvar_vpd_pflags)
VDU 23
VDU 0
VDU vdp_scrpixel
VDU (VDU_BUFFER+0)
VDU (VDU_BUFFER+1)
VDU (VDU_BUFFER+2)
VDU (VDU_BUFFER+3)
$$: BIT.LIL 2, (IX+sysvar_vpd_pflags)
JR Z, $B ; Wait for the result
;
; Return the data as a 1 byte index
;
LD.LIL L, (IX+(sysvar_scrpixelIndex))
POP IX
JP COUNT0
; COLOUR colour
; COLOUR L,P
; COLOUR L,R,G,B
;
COLOUR: CALL EXPRI ; The colour / mode
EXX
LD A, L
LD (VDU_BUFFER+0), A ; Store first parameter
CALL NXT ; Are there any more parameters?
CP ','
JR Z, COLOUR_1 ; Yes, so we're doing a palette change next
;
VDU 11h ; Just set the colour
VDU (VDU_BUFFER+0)
JP XEQ
;
COLOUR_1: CALL COMMA
CALL EXPRI ; Parse R (OR P)
EXX
LD A, L
LD (VDU_BUFFER+1), A
CALL NXT ; Are there any more parameters?
CP ','
JR Z, COLOUR_2 ; Yes, so we're doing COLOUR L,R,G,B
;
VDU 13h ; VDU:COLOUR
VDU (VDU_BUFFER+0) ; Logical Colour
VDU (VDU_BUFFER+1) ; Palette Colour
VDU 0 ; RGB set to 0
VDU 0
VDU 0
JP XEQ
;
COLOUR_2: CALL COMMA
CALL EXPRI ; Parse G
EXX
LD A, L
LD (VDU_BUFFER+2), A
CALL COMMA
CALL EXPRI ; Parse B
EXX
LD A, L
LD (VDU_BUFFER+3), A
VDU 13h ; VDU:COLOUR
VDU (VDU_BUFFER+0) ; Logical Colour
VDU FFh ; Physical Colour (-1 for RGB mode)
VDU (VDU_BUFFER+1) ; R
VDU (VDU_BUFFER+2) ; G
VDU (VDU_BUFFER+3) ; B
JP XEQ
; GCOL mode,colour
;
GCOL: CALL EXPRI ; Parse MODE
EXX
LD A, L
LD (VDU_BUFFER+0), A
CALL COMMA
;
CALL EXPRI ; Parse Colour
EXX
LD A, L
LD (VDU_BUFFER+1), A
;
VDU 12h ; VDU:GCOL
VDU (VDU_BUFFER+0) ; Mode
VDU (VDU_BUFFER+1) ; Colour
JP XEQ
; PLOT mode,x,y
;
PLOT: CALL EXPRI ; Parse mode
EXX
PUSH HL ; Push mode (L) onto stack
CALL COMMA
CALL EXPR_W2 ; Parse X and Y
POP BC ; Pop mode (C) off stack
PLOT_1: VDU 19H ; VDU code for PLOT
VDU C ; C: Mode
VDU E ; DE: X
VDU D
VDU L ; HL: Y
VDU H
JP XEQ
; MOVE x,y
;
MOVE: CALL EXPR_W2 ; Parse X and Y
LD C, 04H ; Plot mode 04H (Move)
JR PLOT_1 ; Plot
; DRAW x1,y1
; DRAW x1,y1,x2,y2
;
DRAW: CALL EXPR_W2 ; Get X1 and Y1
CALL NXT ; Are there any more parameters?
CP ','
LD C, 05h ; Code for LINE
JR NZ, PLOT_1 ; No, so just do DRAW x1,y1
VDU 19h ; Move to the first coordinates
VDU 04h
VDU E
VDU D
VDU L
VDU H
CALL COMMA
PUSH BC
CALL EXPR_W2 ; Get X2 and Y2
POP BC
JR PLOT_1 ; Now DRAW the line to those positions