Added a grayscale/patterened tile fill function.

common/functions.inc

@@ -46,6 +46,7 @@ clearLogo:
 ; Writes a value across 16 bytes, starting at HL. Intended to fill a single tile.
 ; Parameters:
 ;     B - The value to set the bytes to.
+;     HL - Destintion location.
 ; Modifies:
 ;     HL - End result: HL + 16
 fillTile:
@@ -55,6 +56,60 @@ fillTile:
 	pop de
 	ret
 
+; Fills a 16 byte block with a specific pattern. Intended to fill a single tile
+; with a specific grayscale or color shade.
+; Parameters:
+;     B - The pattern to write:
+;           $00: $00 $00
+;           $01: $FF $00
+;           $02: $00 $FF
+;           $03: $FF $FF
+;     HL - Destintion location.
+; Modifies:
+;     B - Set to $00 or $FF.
+;     HL - End result: HL + 16
+fillTileEx:
+	push af
+	ld a, b
+	ld b, %11
+	and b
+	jr nz, _check3
+
+	; b = $00. Fill with plette entry 0.
+	ld b, $00
+	call fillTile
+	pop af
+	ret
+
+_check3:
+	cp b
+	jr nz, _handleAlt
+
+	; b = $ff. Fill with palette entry 3.
+	ld b, $ff
+	call fillTile
+	pop af
+	ret
+
+_handleAlt:
+	push de
+	ld b, %01
+	ld d, 16
+	ld e, $ff
+	cp b
+	ld a, 0
+	jr nz, _fillLoop
+	xor e
+_fillLoop:
+	ld [hli], a
+	xor e
+	dec d
+	jr nz, _fillLoop
+
+	pop de
+	pop af
+	ret
+
 ; Copies up to 256 bytes of memory to another location.
 ; Parameter:
 ;     BC - Source location.

cpu/miscInstrs.asm

@@ -6,7 +6,7 @@ include "common/functions.inc"
 
 SECTION "home", ROM0
 ProgramStart:
-	call clearLogo
+	;call clearLogo
 
 	_lcdDisable
 
@@ -15,20 +15,19 @@ ProgramStart:
 	ldh [$ff47], a
 
 	; TODO: Write actual tests. :)
-	ld a, $ff
-	ld hl, $8014
-	ld [hl], a
-	ld hl, $8016
-	ld [hl], a
-	ld hl, $8019
-	ld [hl], a
-	ld hl, $801b
-	ld [hli], a
-	ld [hli], a
-	ld [hli], a
-	ld [hli], a
-	ld [hli], a
-	call memset
+	ld hl, $8010
+	ld b, $00
+	call fillTileEx
+
+	ld b, $01
+	call fillTileEx
+
+	ld b, $02
+	call fillTileEx
+
+	ld b, $03
+	call fillTileEx
+
 	_lcdEnable
 
 .loop: