8bitworkshop/ecsroot/vcs/kernel.ecs

component Kernel
    lines: 0..255
    bgcolor: 0..255
end

component Bitmap
    bitmapdata: array of 0..255
end

component HasBitmap
    bitmap: [Bitmap]
end

component Colormap
    colormapdata: array of 0..255
end

component HasColormap
    colormap: [Colormap]
end

component Sprite
    height: 0..255
    plyrindex: 0..1
end

component Player end

component PlayerFlags
    plyrflags: 0..63
end

component HasXpos
    xpos: 0..255
end

component HasYpos
    ypos: 0..255
end

component HasXYVel
    xyvel: 0..255
end

system FrameLoop
    on start do once [Kernel] emit (preframe, kernel, postframe)
---
{{@NextFrame}}:
    FRAME_START
    {{!preframe}}
    KERNEL_START
    {{!kernel}}
    KERNEL_END
    {{!postframe}}
    FRAME_END
    lsr SWCHB	    ; test Game Reset switch
    bcs {{@NoStart}}
    jmp Start
{{@NoStart}}:
    jmp {{@NextFrame}}
---
end

system SimpleKernel
    locals 12
    on preframe do each [Sprite,HasBitmap,HasColormap,HasYpos]
---
    lda #192 ; TODO: numlines
    sec
    sbc {{<ypos}}
    sta {{$11}}

    ldy {{<bitmap}}         ; deref
    lda {{<Bitmap.bitmapdata}},y
    sec
    sbc {{$11}}
    sta {{$0}},x
    lda {{>Bitmap.bitmapdata}},y
    sbc #0
    sta {{$2}},x

    ldy {{<colormap}}
    lda {{<Colormap.colormapdata}},y
    sec
    sbc {{$11}}
    sta {{$4}},x
    lda {{>Colormap.colormapdata}},y
    sbc #0
    sta {{$6}},x

    lda {{<height}}
    sta {{$8}},x
    lda {{<ypos}}
    sta {{$10}},x
---
    on preframe do once [Sprite,HasBitmap,HasColormap,HasYpos]
---
; L0 L1 H0 H1 -> L0 H0 L1 H1
    lda {{$1}}
    ldy {{$2}}
    sty {{$1}}
    sta {{$2}}
    lda {{$5}}
    ldy {{$6}}
    sty {{$5}}
    sta {{$6}}
---
    on kernel do once [Kernel]
---
    lda {{<bgcolor}}
    sta COLUBK
    ldy {{<lines}}
@LVScan:
    lda {{$8}} ; height
    dcp {{$10}} ; ypos
    bcs @DoDraw1
    lda #0
    .byte $2C
@DoDraw1:
    lda ({{$0}}),y
    sta WSYNC
    sta GRP0
    lda ({{$4}}),y
    sta COLUP0

    lda {{$9}} ; height
    dcp {{$11}} ; ypos
    bcs @DoDraw2
    lda #0
    .byte $2C
@DoDraw2:
    lda ({{$2}}),y
    sta GRP1
    lda ({{$6}}),y
    sta COLUP1

    dey		; decrement
    bne @LVScan	; repeat until 192 lines
---
end

system SetXPos
    on preframe do each [Sprite,HasXpos] emit (SetHorizPos)
---
    lda {{<xpos}}
    ldy {{<plyrindex}}
    sta HMCLR
    jsr {{^SetHorizPos}}
---
end

system SetHorizPos
    on SetHorizPos do once [HasXpos]
---
; SetHorizPos routine
; A = X coordinate
; Y = player number (0 or 1)
SetHorizPos:
	sta WSYNC	; start a new line
	sec		    ; set carry flag
    nop
@DivideLoop:
	sbc #15		; subtract 15
	bcs @DivideLoop	; branch until negative
	eor #7		; calculate fine offset
	asl
	asl
	asl
	asl
	sta RESP0,y	; fix coarse position
	sta HMP0,y	; set fine offset
    sta WSYNC
    sta HMOVE
	rts		; return to caller
---
end

system JoyRead
    locals 1
    on postframe do once [Player]
---
    lda SWCHA
    sta {{$0}}
---
    on postframe do each [Player] emit (joyup, joydown, joyleft, joyright, joybutton)
---
    asl {{$0}}
    bcs {{@SkipMoveRight}}
    {{!joyright}}
{{@SkipMoveRight}}:
    asl {{$0}}
    bcs {{@SkipMoveLeft}}
    {{!joyleft}}
{{@SkipMoveLeft}}:
    asl {{$0}}
    bcs {{@SkipMoveDown}}
    {{!joydown}}
{{@SkipMoveDown}}:
    asl {{$0}}
    bcs {{@SkipMoveUp}}
    {{!joyup}}
{{@SkipMoveUp}}:
---
end

system MoveJoyX
    on joyleft do source [HasXpos]
---
    lda {{<xpos}}
    sec
    sbc #1
    bcc {{@nomove}}
    sta {{<xpos}}
{{@nomove}}:
---
    on joyright do source [HasXpos]
---
    lda {{<xpos}}
    clc
    adc #1
    cmp #150
    bcs {{@nomove}}
    sta {{<xpos}}
{{@nomove}}:
---
end

system MoveJoyY
    on joyup do source [HasYpos]
---
    lda {{<ypos}}
    sec
    sbc #1
    bcc {{@nomove}}
    sta {{<ypos}}
{{@nomove}}:
---
    on joydown do source [HasYpos]
---
    lda {{<ypos}}
    clc
    adc #1
    cmp #150
    bcs {{@nomove}}
    sta {{<ypos}}
{{@nomove}}:
---
end

scope Main
    entity Kernel [Kernel]
        const lines = 192
        const bgcolor = 0xa2
    end
    entity Bitmap1 [Bitmap]
        const bitmapdata = [1, 1, 3, 7, 15, 31, 63, 127]
    end
    entity Bitmap2 [Bitmap]
        const bitmapdata = [$18,$3e,$ff,$ff,$ff,$ff,$3e,$18]
    end
    entity Colormap1 [Colormap]
        const colormapdata = [6, 3, 6, 9, 12, 14, 31, 63]
    end
    entity Player0 [Sprite,HasBitmap,HasColormap,HasXpos,HasYpos,Player]
        const plyrindex = 0
        init height = 8
        init xpos = 50
        init ypos = 50
    end
    entity Player1 [Sprite,HasBitmap,HasColormap,HasXpos,HasYpos,Player]
        const plyrindex = 1
        init height = 8
        init xpos = 100
        init ypos = 60
        init bitmap = #Bitmap2
    end
end