some tidying (nw)

src/devices/sound/nes_apu.h

@@ -52,8 +52,8 @@ public:
 	nesapu_device(const machine_config &mconfig, const char *tag, device_t *owner, u32 clock);
 
 	// static configuration helpers
-	template<class _Object> static devcb_base &set_irq_handler(device_t &device, _Object object) { return downcast<nesapu_device &>(device).m_irq_handler.set_callback(object); }
+	template <class Object> static devcb_base &set_irq_handler(device_t &device, Object &&cb) { return downcast<nesapu_device &>(device).m_irq_handler.set_callback(std::forward<Object>(cb)); }
-	template<class _Object> static devcb_base &set_mem_read_callback(device_t &device, _Object object) { return downcast<nesapu_device &>(device).m_mem_read_cb.set_callback(object); }
+	template <class Object> static devcb_base &set_mem_read_callback(device_t &device, Object &&cb) { return downcast<nesapu_device &>(device).m_mem_read_cb.set_callback(std::forward<Object>(cb)); }
 
 	virtual void device_clock_changed() override;
 

src/devices/video/ppu2c0x_vt.cpp

@@ -128,33 +128,65 @@ void ppu_vt03_device::read_sprite_plane_data(int address)
 	m_va34 = 0;
 	m_planebuf[0] = m_read_sp((address + 0) & 0x1fff);
 	m_planebuf[1] = m_read_sp((address + 8) & 0x1fff);
+
+	int is4bpp = get_201x_reg(0x0) & 0x04;
+	
+	if (is4bpp)
+	{
 		m_va34 = 1;
 		m_extplanebuf[0] = m_read_sp((address + 0) & 0x1fff);
 		m_extplanebuf[1] = m_read_sp((address + 8) & 0x1fff);
 	}
+}
 
 void ppu_vt03_device::make_sprite_pixel_data(uint8_t &pixel_data, int flipx)
 {
 	ppu2c0x_device::make_sprite_pixel_data(pixel_data, flipx);
 
+	int is4bpp = get_201x_reg(0x0) & 0x04;
+
+	if (is4bpp)
+	{
 		if (flipx)
 		{
-		pixel_data |= (((m_extplanebuf[0] & 1) << 5) | ((m_extplanebuf[1] & 1) << 6)); // yes, shift by 5 and 6 because of the way the palette is arranged in RAM
+			// yes, shift by 5 and 6 because of the way the palette is arranged in RAM
+			pixel_data |= (((m_extplanebuf[0] & 1) << 5) | ((m_extplanebuf[1] & 1) << 6)); 
 			m_extplanebuf[0] = m_extplanebuf[0] >> 1;
 			m_extplanebuf[1] = m_extplanebuf[1] >> 1;
 		}
 		else
 		{
-		pixel_data |= (((m_extplanebuf[0] >> 7) & 1) << 5) | (((m_extplanebuf[1] >> 7) & 1) << 6); // yes, shift by 5 and 6 because of the way the palette is arranged in RAM
+			pixel_data |= (((m_extplanebuf[0] >> 7) & 1) << 5) | (((m_extplanebuf[1] >> 7) & 1) << 6);
 			m_extplanebuf[0] = m_extplanebuf[0] << 1;
 			m_extplanebuf[1] = m_extplanebuf[1] << 1;
 		}
 	}
+}
 
 void ppu_vt03_device::draw_sprite_pixel(int sprite_xpos, int color, int pixel, uint8_t pixel_data, bitmap_ind16& bitmap)
+{
+	int is4bpp = get_201x_reg(0x0) & 0x04;
+	int is16pix = get_201x_reg(0x0) & 0x01;
+
+	if (is4bpp)
+	{
+		if (!is16pix)
 		{
 			bitmap.pix16(m_scanline, sprite_xpos + pixel) = pixel_data + (4 * color);
 		}
+		else
+		{
+			/* this mode makes use of the extra planes to increase sprite width instead
+			   we probably need to split them out again and draw them at xpos+8 with a
+			   cliprect - not seen used yet */
+			bitmap.pix16(m_scanline, sprite_xpos + pixel) = pixel_data + (machine().rand()&3);
+		}
+	}
+	else
+	{
+		ppu2c0x_device::draw_sprite_pixel(sprite_xpos, color, pixel, pixel_data, bitmap);
+	}
+}
 
 void ppu_vt03_device::read_tile_plane_data(int address, int color)
 {

src/devices/video/ppu2c0x_vt.h

@@ -9,7 +9,11 @@
 
 ******************************************************************************/
 
-#include "emu.h"
+#ifndef MAME_VIDEO_PPU_VT03_H
+#define MAME_VIDEO_PPU_VT03_H
+
+#pragma once
+
 #include "video/ppu2c0x.h"
 
 #define MCFG_PPU_VT03_ADD(_tag)   \
@@ -25,8 +29,8 @@ class ppu_vt03_device : public ppu2c0x_device {
 public:
 	ppu_vt03_device(const machine_config &mconfig, const char *tag, device_t *owner, uint32_t clock);
 
-	template<class _Object> static devcb_base &set_read_bg_callback(device_t &device, _Object object) { return downcast<ppu_vt03_device &>(device).m_read_bg.set_callback(object); }
+	template <class Object> static devcb_base &set_read_bg_callback(device_t &device, Object &&cb) { return downcast<ppu_vt03_device &>(device).m_read_bg.set_callback(std::forward<Object>(cb)); }
-	template<class _Object> static devcb_base &set_read_sp_callback(device_t &device, _Object object) { return downcast<ppu_vt03_device &>(device).m_read_sp.set_callback(object); }
+	template <class Object> static devcb_base &set_read_sp_callback(device_t &device, Object &&cb) { return downcast<ppu_vt03_device &>(device).m_read_sp.set_callback(std::forward<Object>(cb)); }
 
 	virtual DECLARE_READ8_MEMBER(read) override;
 	virtual DECLARE_WRITE8_MEMBER(write) override;
@@ -76,3 +80,5 @@ private:
 };
 
 DECLARE_DEVICE_TYPE(PPU_VT03,    ppu_vt03_device)
+
+#endif // MAME_VIDEO_PPU_VT03_H

src/mame/drivers/nes_vt.cpp

@@ -366,7 +366,7 @@ void nes_vt_state::machine_reset()
 
 int nes_vt_state::calculate_real_video_address(int addr, int extended, int readtype)
 {
-	// might be a VT09 only feature (8bpp or 4bpp direct colour mode??)
+	// might be a VT09 only feature (8bpp?) but where are the other 4 bits?
 	int alt_order = m_ppu->get_201x_reg(0x0) & 0x40;
 
 	if (readtype == 0)