background sprites working in ppusim

1 files changed, 44 insertions, 1 deletions

diff --git a/src/ppusim/pixel.c b/src/ppusim/pixel.c
index 3a09ccd..96ee998 100644
--- a/src/ppusim/pixel.c
+++ b/src/ppusim/pixel.c
@@ -1,6 +1,10 @@
 #include <SDL2/SDL.h>
+#include <stdbool.h>
 
+#include "ppu/internals.h"
+#include "ppusim/mem.h"
 #include "ppusim/sim.h"
+#include "ppu/consts.h"
 
 static void hh_ppusim_draw(SDL_Renderer* r, unsigned px, unsigned py, unsigned cr, unsigned cg, unsigned cb) {
 	SDL_SetRenderDrawColor(r, cr, cg, cb, 255);
@@ -12,11 +16,50 @@ static void hh_ppusim_draw(SDL_Renderer* r, unsigned px, unsigned py, unsigned c
 	});
 }
 
+/* transform xy if tile is flipped */
+static uint16_t hh_ppusim_apply_transform(unsigned x, unsigned y, bool fliph, bool flipv) {
+	unsigned tx = fliph ? HH_PPU_SPRITE_WIDTH - x - 1 : x;
+	unsigned ty = flipv ? HH_PPU_SPRITE_HEIGHT - y - 1 : y;
+	return ty * HH_PPU_SPRITE_WIDTH + tx;
+}
+
+/* @brief get current bg pixel cidx */
+static uint8_t hh_ppusim_bg_pixel(unsigned x, unsigned y) {
+	hh_ppu_data_t* aux = &g_hh_ppusim_vram[HH_PPU_VRAM_AUX_OFFSET];
+	unsigned bg_shift_y = HH_RESIZE(aux[0], 7, 0);
+	unsigned bg_shift_x = HH_RESIZE(aux[0], 15, 8) | HH_RESIZE(aux[1], 0, 0) << 8;
+	unsigned abs_x = bg_shift_x + x;
+	unsigned abs_y = bg_shift_y + y;
+	unsigned grid_x = abs_x / HH_PPU_SPRITE_WIDTH;
+	unsigned grid_y = abs_y / HH_PPU_SPRITE_HEIGHT;
+	unsigned loc_x = abs_x - grid_x * HH_PPU_SPRITE_WIDTH;
+	unsigned loc_y = abs_y - grid_y * HH_PPU_SPRITE_HEIGHT;
+	unsigned bam_offset = grid_y * HH_PPU_BG_CANVAS_TILES_H + grid_x;
+	hh_ppu_data_t bam = g_hh_ppusim_vram[HH_PPU_VRAM_BAM_OFFSET + bam_offset];
+	uint8_t cidx = 0;
+	uint16_t tile_pixel_idx = hh_ppusim_apply_transform(loc_x, loc_y, HH_RESIZE(bam, 14, 14), HH_RESIZE(bam, 13, 13));
+	uint16_t tile_idx = HH_RESIZE(bam, 9, 0);
+	hh_ppu_addr_t ttm_addr = tile_idx + tile_pixel_idx / 5;
+	uint8_t word_bit_addr = (tile_pixel_idx % 5) * 3;
+	hh_ppu_data_t tmm = g_hh_ppusim_vram[HH_PPU_VRAM_TMM_OFFSET + ttm_addr];
+	cidx |= HH_RESIZE(bam, 12, 10) << 3;
+	cidx |= HH_RESIZE(tmm, word_bit_addr+2, word_bit_addr) << 0;
+	return cidx;
+}
+
 void hh_ppusim_pixel(SDL_Renderer* r, unsigned x, unsigned y) {
 	// loop through foreground sprites to get highest priority cidx
-	// get background cidx
+	uint8_t bg_cidx = hh_ppusim_bg_pixel(x, y);
 	// check if palette color cidx of foreground is 0
 	// lookup color from PAL
 	// hh_ppusim_draw
+	uint8_t cidx = bg_cidx;
+	hh_ppu_data_t pal_rgb = g_hh_ppusim_vram[HH_PPU_VRAM_PAL_OFFSET + cidx];
+	hh_ppu_rgb_color_t rgb = {
+		HH_RESIZE(pal_rgb, 11, 8),
+		HH_RESIZE(pal_rgb, 7, 4),
+		HH_RESIZE(pal_rgb, 3, 0)
+	};
+	hh_ppusim_draw(r, x, y, rgb[0] << 4, rgb[1] << 4, rgb[2] << 4);
 }