Working terrain scrolling

gscats.s

@@ -30,36 +30,82 @@ mainBank2:
 	jsr colorFill
 
 	jsr generateTerrain
+
+mainGameLoop:
+	ldy mapScrollPos
 	jsr renderTerrainColumns
 
-	jsr kbdWait
-	CLASSICVIDEO
+	jsr kbdScan
 
+	lda quitRequested
+	beq mainGameLoop
+
+
+	CLASSICVIDEO
 	jml (proDOSLongJump)
 
 
 
 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
-; kbdWait
-; Waits for a keystroke
+; kbdScan
+; Processes keyboard input
 ;
-kbdWait:
+; Trashes A
+;
+
+kbdScan:
 	EMULATION
 
-kbdWaitLoop:
+kbdScanLoop:
 	lda KBD
-	bpl kbdWaitLoop
+	bpl kbdScanLoop
 	sta KBDSTROBE
 
+	cmp #(8 + $80)
+	beq kbdScanLeftArrow
+
+	cmp #(21 + $80)
+	beq kbdScanRightArrow
+
+	cmp #(32 + $80)
+	beq kbdScanSpace
 	NATIVE
+
+kbdScanDone:
 	rts
 
+kbdScanLeftArrow:
+	NATIVE
+	lda mapScrollPos
+	beq kbdScanDone
+	dec
+	sta mapScrollPos
+	bra kbdScanDone
+
+kbdScanRightArrow:
+	NATIVE
+	lda mapScrollPos
+	cmp #TERRAINWIDTH/4-80
+	beq kbdScanDone
+	inc
+	sta mapScrollPos
+	bra kbdScanDone
+
+kbdScanSpace:
+	NATIVE
+	lda #1
+	sta quitRequested
+	bra kbdScanDone
+
 
 
 
 basePalette:
 	.word $0000,$0080,$0000,$000F,$0000,$0000,$0000,$0000,$0000,$0000,$0000,$0000,$0000,$0000,$0000,$0000
-
+mapScrollPos:	; 4-pixel columns
+	.word $0000
+quitRequested:
+	.word $0000
 
 .include "graphics.s"
 .include "terrain.s"

terrain.s

@@ -5,8 +5,8 @@
 ;
 
 
-TERRAINWIDTH = 320		; In pixels
-MAXTERRAINHEIGHT = 80	; In pixels
+TERRAINWIDTH = 640		; In pixels
+MAXTERRAINHEIGHT = 128	; In pixels
 
 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
 ; renderTerrainColumn
@@ -30,15 +30,23 @@ renderTerrainColumn:
 	sta renderTerrainColumnSMC+1
 	pha		; Cache 16-bit VRAM pointer on the stack
 
-	lda terrainData,y
+	lda terrainData,y		; Cache terrain height on the stack
 	and #$00ff
-	tax
-	inx		; Prevent x from going negative upon entry to loop
+	sta renderTerrainColumnHeight
+	ldx #0
 
 renderTerrainColumnLoop:
-	dex
+	inx
+	cpx #MAXTERRAINHEIGHT
 	beq renderTerrainColumnDone
+	cpx renderTerrainColumnHeight
+	bpl renderTerrainColumnBlack
+
 	lda #$1111
+	bra renderTerrainColumnSMC
+
+renderTerrainColumnBlack:
+	lda #$0000
 
 renderTerrainColumnSMC:
 	sta $e19c60
@@ -53,23 +61,32 @@ renderTerrainColumnDone:
 	pla
 	rts
 
-
+renderTerrainColumnHeight:
+	.word 0
 
 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
 ; renderTerrainColumns
 ;
 ; This is not fast- probably only useful for debugging
 ;
+; Y = Start column
+;
+; Trashes all registers
+;
 
 renderTerrainColumns:
 	LOADPARAM24 $e1e1,$9c60
-	ldy #0
+	tya
+	clc
+	adc #80
+	sta SCRATCHL
 
 renderTerrainColumnsLoop:
 	jsr renderTerrainColumn
 	iny
-	cpy #TERRAINWIDTH/4
+	cpy SCRATCHL
 	beq renderTerrainColumnsDone
+
 	inc PARAM24
 	inc PARAM24
 	bra renderTerrainColumnsLoop
@@ -109,6 +126,6 @@ generateTerrainLoop:
 ; Terrain data, stored as height values 4 pixels wide
 
 terrainData:
-	.repeat TERRAINWIDTH/4
+	.repeat TERRAINWIDTH/2
 	.byte 0
 	.endrepeat