Sprites and initial workout in understanding how scroll works (nw)

src/mame/drivers/metlfrzr.cpp

@@ -6,12 +6,13 @@
 	
 	preliminary driver by Angelo Salese
 	
-	HW seems the natural evolution of Dark Mist type HW.
+	HW seems the natural evolution of Dark Mist type.
 	
 	TODO:
 	- T5182 hookup, controls sound and coin inputs. With current hookup it accepts coins but not fully, and sound isn't working at all ...
-	- Sprites, 0xfe00-0xffff? (And why game doesn't actually write at 0xff80-0xffff?)
-	- Foreground rowscroll / per-tile scroll;
+	- Still various unused bits. 
+	- Nuke legacy video code and re-do it by using tilemap system.
+	- sprites are ahead of 1/2 frames;
 	- Writes at 0xb800-0xbfff at attract mode gameplay demo transition?
 
 ****************************************/
@@ -30,6 +31,7 @@ public:
 		m_decrypted_opcodes(*this, "decrypted_opcodes"),
 		m_work_ram(*this, "wram"),
 		m_vram(*this, "vram"),
+		m_video_regs(*this, "vregs"),
 		m_palette(*this, "palette"),
 		m_gfxdecode(*this, "gfxdecode")
 		{ }
@@ -45,6 +47,7 @@ public:
 	required_shared_ptr<UINT8> m_decrypted_opcodes;
 	required_shared_ptr<UINT8> m_work_ram;
 	required_shared_ptr<UINT8> m_vram;
+	required_shared_ptr<UINT8> m_video_regs;
 	required_device<palette_device> m_palette;
 	required_device<gfxdecode_device> m_gfxdecode;
 
@@ -59,39 +62,80 @@ void metlfrzr_state::video_start()
 {
 }
 
+/*
+ - video regs format:
+	[0x06] ---- --x- used during title screen transition, unknown purpose
+	[0x06] ---- ---x 
+	[0x15] always 0?
+	[0x16] always 0?
+	[0x17] xxxx xxxx X scrolling base value
+	Notice that it's currently unknown how the game is really supposed to NOT enable scrolling during gameplay.
+ */
 void metlfrzr_state::legacy_bg_draw(bitmap_ind16 &bitmap,const rectangle &cliprect)
 {
 	gfx_element *gfx = m_gfxdecode->gfx(m_fg_tilebank);
+	const UINT16 vram_mask = m_vram.mask() >> 1;
 	int count;
-
+	int x_scroll_base;
+	int x_scroll_shift;
+	UINT16 x_scroll_value;
+	x_scroll_value = m_video_regs[0x17] + ((m_video_regs[0x06] & 1) << 8);
+	x_scroll_base = (x_scroll_value >> 3) * 32;
+	x_scroll_shift = (x_scroll_value & 7);
+	
 	for (count=0;count<32*32;count++)
 	{
+		int tile_base = count;
 		int y = (count % 32);
-		int x = count / 32;
+		if(y > 7 || m_video_regs[0x06] & 3) // TODO: this condition breaks on level 5 halfway thru.
+			tile_base+= x_scroll_base;
+		else
+			x_scroll_shift = 0;
+		tile_base &= vram_mask;
+		int x = (count / 32);
 
-		UINT16 tile = m_vram[count*2+0] + ((m_vram[count*2+1] & 0xf0) << 4);
-		UINT8 color = m_vram[count*2+1] & 0xf;
+			
+		UINT16 tile = m_vram[tile_base*2+0] + ((m_vram[tile_base*2+1] & 0xf0) << 4);
+		UINT8 color = m_vram[tile_base*2+1] & 0xf;
 		
-		gfx->transpen(bitmap,cliprect,tile,color,0,0,x*8,y*8,0xf);
+		gfx->transpen(bitmap,cliprect,tile,color,0,0,x*8-x_scroll_shift,y*8,0xf);
 	}
 
 }
 
+/*
+ sprite DMA:
+	0xfe00-0xffff contains buffer for data to be copied.
+	Sprites are currently lagging (noticeable during scrolling) therefore there must be either an automatic or manual trigger.
+	Sprite seems to traverse from top to bottom priority-wise, other than that format is almost 1:1 with darkmist.cpp.
+ sprite format:
+	[0] tttt tttt tile number
+	[1] x--- ---- if 1 sprite is disabled
+	[1] -ttt ---- tile bank
+	[1] ---- cccc palette number
+	[2] yyyy yyyy Y offset
+	[3] xxxx xxxx X offset	
+*/
 void metlfrzr_state::legacy_obj_draw(bitmap_ind16 &bitmap,const rectangle &cliprect)
 {
-	gfx_element *gfx = m_gfxdecode->gfx(3);
+	gfx_element *gfx_2 = m_gfxdecode->gfx(2);
+	gfx_element *gfx_3 = m_gfxdecode->gfx(3);
 	int count;
 	UINT8 *base_spriteram = m_work_ram + 0xe00;
-
-	for(count=0;count<0x200;count+=4)
+	
+	for(count=0x200-4;count>-1;count-=4)
 	{
-		UINT8 tile_bank = 0;//base_spriteram[count+1] & 3;
+		if(base_spriteram[count+1] & 0x80)
+			continue;
+		
+		gfx_element *cur_gfx = base_spriteram[count+1] & 0x40 ? gfx_3 : gfx_2;
+		UINT8 tile_bank = (base_spriteram[count+1] & 0x30) >> 4;
 		UINT16 tile = base_spriteram[count] | (tile_bank << 8);
 		UINT8 color = base_spriteram[count+1] & 0xf;
 		int y = base_spriteram[count+2];
 		int x = base_spriteram[count+3];
 	
-		gfx->transpen(bitmap,cliprect,tile,color,0,0,x,y,0xf);
+		cur_gfx->transpen(bitmap,cliprect,tile,color,0,0,x,y,0xf);
 	}
 }
 
@@ -107,12 +151,12 @@ UINT32 metlfrzr_state::screen_update_metlfrzr(screen_device &screen, bitmap_ind1
 WRITE8_MEMBER(metlfrzr_state::output_w)
 {
 	// bit 7: flip screen
-	// bit 5: on title screen after coin is inserted
+	// bit 5: on title screen after coin is inserted.
 	// bit 1-0: unknown purpose, both 1s too generally
 	m_fg_tilebank = (data & 0x10) >> 4;
 	membank("bank1")->set_entry((data & 0xc) >> 2);
 
-	popmessage("%02x",data & 3);
+	//popmessage("%02x",data & 3);
 	if(data & 0x60)
 		printf("%02x\n",data);
 }
@@ -131,7 +175,7 @@ static ADDRESS_MAP_START( metlfrzr_map, AS_PROGRAM, 8, metlfrzr_state )
 	AM_RANGE(0xd602, 0xd602) AM_READ_PORT("START")
 	AM_RANGE(0xd603, 0xd603) AM_READ_PORT("DSW1")
 	AM_RANGE(0xd604, 0xd604) AM_READ_PORT("DSW2")
-	// d600-0d61f scroll area?
+	AM_RANGE(0xd600, 0xd61f) AM_RAM AM_SHARE("vregs") // TODO: write-only, debug
 	
 	AM_RANGE(0xd700, 0xd700) AM_WRITE(output_w)
 	AM_RANGE(0xd710, 0xd710) AM_DEVWRITE("t5182", t5182_device, sound_irq_w)