Progress on ppu

include/gb.h

@@ -92,9 +92,12 @@ enum {
 	GB_PPU_N_REGS,
 };
 
+#define	GB_PPU_LCDC_BGW_ENABLE		0x1
+#define	GB_PPU_LCDC_OBJ_ENABLE		0x2
 #define	GB_PPU_LCDC_BIG_OBJ		0x4
 #define	GB_PPU_LCDC_BG_TILE_MAP		0x8
 #define	GB_PPU_LCDC_TILE_BASE		0x10
+#define	GB_PPU_LCDC_WIN_ENABLE		0x20
 #define	GB_PPU_LCDC_WIN_TILE_MAP	0x40
 
 enum {
@@ -123,12 +126,18 @@ typedef struct pixel_fifo_fetcher_t {
 	ut8 state_ctr;
 } PixelFifoFetcher;
 
+
+// flags
 #define	GB_PIXEL_FIFO_FETCH_OBJECT	0x10
 #define	GB_PIXEL_FIFO_FETCH_WINDOW	0x20
 #define	GB_PIXEL_FIFO_FETCH_READY	0x40
 //specifies if scx & 0x7 and wy are copied into fifo
 #define GB_PIXEL_FIFO_REG_DATA_LOADED	0x80
 
+//flags1
+//window x condition triggered
+#define	GB_PIXEL_FIFO_WXC_TRIGGERED	0x8
+
 #define	GB_OAM_PALLET	0x10
 #define	GB_OAM_FLIP_X	0x20
 #define	GB_OAM_FLIP_Y	0x40
@@ -159,7 +168,10 @@ obj p1	-	11
 	ut8 n_fpixel;	//number of pixel that are currently in the fifo
 	ut8 x;
 	ut8 wy;
+	union {
 		ut8 dx;		//discard x
+		ut8 flags1;
+	};
 } PixelFifo;
 
 typedef struct gb_dmg_ppu_t {

io/ppu.c

@@ -197,18 +197,30 @@ static void read_obj_data (GBPPU *ppu, RIO *io, ut8 *tile, int oam_fd) {
 	}
 }
 
-static void gb_ppu_pixel_fifo_merge_opixels (PixelFifo *pxf) {
+static void gb_ppu_pixel_fifo_merge_opixels (PixelFifo *pxf, bool priority) {
 	ut32 pixels = pxf->data >> 32;
-	ut32 newpixels = 0;
+	ut64 newpixels = 0;
 	ut32 i;
 	for (i = 0; i < 8; i++) {
-		if (!(pixels & (0x3 << 28))) {	//check for transparency
+		const ut8 bg_pixel = (pixels & (0xf << ((7 - i) << 2))) >> ((7 - i) << 2);
-			newpixels = (newpixels << 4) |
+		const ut8 fg_pixel = (pxf->fetcher[1].fetched & (0xf << ((7 - i) << 2))) >> ((7 - i) << 2);
-				((pxf->fetcher[1].fetched & (0xf << (i << 2))) >> (i << 2));
+		newpixels <<= 4;
-			pixels = pixels << 4;
+		//background always wins if obj is transparent or bg is obj
+		if ((!(fg_pixel & 0x3)) || ((bg_pixel & 0xc) == 0x4) || (bg_pixel & 0x8)) {
+			newpixels |= bg_pixel;
 			continue;
 		}
+		if ((bg_pixel & 0xc) == 0x4) {
+			//bg is window
+			//TODO: check for window priority
 		}
+		if (!priority && (bg_pixel & 0x3)) {
+			newpixels |= bg_pixel;
+			continue;
+		}
+		newpixels |= fg_pixel;
+	}
+	pxf->data = (pxf->data & 0xffffffff) | (newpixels << 32);
 }
 
 static void gb_pixel_fifo_fetch_continue (GB *gb) {
@@ -351,16 +363,22 @@ static void shit_out_pixel (GBPPU *ppu) {
 	ppu->fifo.shift_out = (ppu->fifo.shift_out & 0xf0) | ppu->fifo.data >> 60;
 	ppu->fifo.data = ppu->fifo.data << 4;
 	ppu->fifo.n_fpixel--;
-	if (ppu->fifo.dx) {
+	if (ppu->fifo.dx & 0x7) {
 		//discard pixel
-		ppu->fifo.dx--;
+		ppu->fifo.dx = (ppu->fifo.dx & 0xf8) | ((ppu->fifo.dx & 0x7) - 1);
 		return;
 	}
 	ut8 color;
-	if (!(ppu->fifo.shift_out & 0x08)) {
 	//bg pallet
+	if (!(ppu->fifo.shift_out & 0x08)) {
+		//check if window and bg are enabled
+		if (ppu->buf[GB_PPU_LCDC] & GB_PPU_LCDC_BGW_ENABLE) {
 			color = (ppu->buf[GB_PPU_BGP] & (0x3 << ((ppu->fifo.shift_out & 0x3) << 1))) >>
 				((ppu->fifo.shift_out & 0x3) << 1);
+		} else {
+			//white
+			color = 0;
+		}
 	} else {
 		const ut8 pal = !!(ppu->fifo.shift_out & 0x04);
 		color = (ppu->buf[GB_PPU_OBP0 + pal] & (0x3 << ((ppu->fifo.shift_out & 0x3) << 1))) >>
@@ -390,6 +408,29 @@ static ut32 gb_ppu_render_continue (GB *gb, ut32 cycles) {
 		fifo->flags |= GB_PIXEL_FIFO_REG_DATA_LOADED;
 	}
 	while (cycles) {
+#if 1
+		if (fifo->flags & GB_PIXEL_FIFO_FETCH_WINDOW) {
+			//this is probably insufficient,
+			//but the actual behaviour of deactivating the window mid fetch is not really documented
+			if (!(gb->ppu->buf[GB_PPU_LCDC] & GB_PPU_LCDC_WIN_ENABLE)) {
+				fifo->flags ^= GB_PIXEL_FIFO_FETCH_WINDOW;
+			}
+		} else {
+			if (gb->ppu->buf[GB_PPU_LCDC] & GB_PPU_LCDC_WIN_ENABLE) {
+				if ((fifo->wy <= gb->ppu->buf[GB_PPU_LY]) &&
+					((fifo->flags1 & GB_PIXEL_FIFO_WXC_TRIGGERED) ||
+					(gb->ppu->buf[GB_PPU_WX] >= fifo->x))) {
+					//when window starts at 0, we don't need to discard pixels anyway
+					fifo->flags1 = GB_PIXEL_FIFO_WXC_TRIGGERED;
+					fifo->flags |= GB_PIXEL_FIFO_FETCH_WINDOW;
+					//clear the fetcher
+					fifo->fetcher[0] = (const PixelFifoFetcher) {0};
+					//clear the pipe
+					fifo->n_fpixel = 0;
+				}
+			}
+		}
+#endif
 		if (fifo->n_fpixel < 9) {
 			//initial phase on each line
 			//also when window starts?
@@ -422,7 +463,9 @@ static ut32 gb_ppu_render_continue (GB *gb, ut32 cycles) {
 			} else {
 				gb_pixel_fifo_fetch_continue (gb);
 				if (fifo->flags & GB_PIXEL_FIFO_FETCH_READY) {
-					gb_ppu_pixel_fifo_merge_opixels (fifo);
+					if (gb->ppu->buf[GB_PPU_LCDC] & GB_PPU_LCDC_OBJ_ENABLE) {
+						gb_ppu_pixel_fifo_merge_opixels (fifo, !!(fifo->obj & GB_FIFO_OAM_PRIORITY));
+					}
 					fifo->flags ^= GB_PIXEL_FIFO_FETCH_OBJECT | GB_PIXEL_FIFO_FETCH_READY;
 				}
 			}