add gpu_draw_objs()

1 files changed, 94 insertions, 49 deletions

diff --git a/ops.yaml b/ops.yaml
index a88e9e4..0c50cee 100644
--- a/ops.yaml
+++ b/ops.yaml
@@ -10247,6 +10247,16 @@ templates:
     }
 
     static uint16_t
+    obj_get_tile_addr(
+      gb_t * const ctx,
+      const uint8_t tile
+    ) {
+      UNUSED(ctx);
+      // base: 0x8000, tile is unsigned
+      return 0x8000 + 16 * tile;
+    }
+
+    static uint16_t
     bg_get_tile_addr(
       gb_t * const ctx,
       const uint8_t ty,
@@ -10311,41 +10321,97 @@ templates:
     }
 
     static void
+    gpu_draw_objs(
+      gb_t * const ctx,
+      const bool priority
+    ) {
+      for (uint8_t i = 0; i < 40; i++) {
+        if (
+          // sprite has correct priority
+          (ctx->gpu.oam_cache[i].priority == priority) &&
+
+          // sprite is on screen and visible
+          BETWEEN(ctx->gpu.oam_cache[i].y, 0, 144) &&
+          BETWEEN(ctx->gpu.oam_cache[i].x, 0, 160) &&
+
+          // sprite is on current line
+          BETWEEN(ctx->gpu.line, ctx->gpu.oam_cache[i].y, ctx->gpu.oam_cache[i].y + 8)
+        ) {
+          // get tile row data
+          const uint16_t row = mmu_rw(ctx, (
+            // get tile data address
+            obj_get_tile_addr(ctx, ctx->gpu.oam_cache[i].tile) +
+
+            // calculate row offset within tile data
+            (2 * (ctx->gpu.line - ctx->gpu.oam_cache[i].y))
+          ));
+
+          for (uint8_t j = 0; j < 8; j++) {
+            const int16_t sx = ctx->gpu.oam_cache[i].x + j;
+
+            if (BETWEEN(sx, 0, 160)) {
+              // get palette offset for pixel
+              const uint8_t p_ofs = (
+                ((row >> (8 + (7 - j)) & 0x01) << 1) |
+                ((row >> (7 - j)) & 0x01)
+              );
+
+              // get pixel color
+              if (p_ofs > 0) {
+                // get object palette
+                const uint8_t obp = ((ctx->gpu.oam_cache[i].palette) ? ctx->gpu.obp1 : ctx->gpu.obp0);
+                // get pixel color
+                const uint8_t pc = (obp >> (2 * p_ofs)) & 0x03;
+
+                // calculate framebuffer offset
+                const uint16_t fb_ofs = 3 * (160 * ctx->gpu.line + sx);
+
+                // convert from 0-3 to RGB
+                switch (pc) {
+                case 0:
+                  ctx->gpu.fb[fb_ofs + 0] = 0xFF;
+                  ctx->gpu.fb[fb_ofs + 1] = 0xFF;
+                  ctx->gpu.fb[fb_ofs + 2] = 0xFF;
+                  break;
+                case 1:
+                  ctx->gpu.fb[fb_ofs + 0] = 0xC0;
+                  ctx->gpu.fb[fb_ofs + 1] = 0xC0;
+                  ctx->gpu.fb[fb_ofs + 2] = 0xC0;
+                  break;
+                case 2:
+                  ctx->gpu.fb[fb_ofs + 0] = 0x40;
+                  ctx->gpu.fb[fb_ofs + 1] = 0x40;
+                  ctx->gpu.fb[fb_ofs + 2] = 0x40;
+                  break;
+                case 3:
+                  ctx->gpu.fb[fb_ofs + 0] = 0x00;
+                  ctx->gpu.fb[fb_ofs + 1] = 0x00;
+                  ctx->gpu.fb[fb_ofs + 2] = 0x00;
+                  break;
+                }
+              }
+            }
+          }
+        }
+      }
+    }
+
+    static void
     gpu_draw_line(
       gb_t * const ctx
     ) {
       if (gpu_is_active(ctx)) {
         gpu_oam_cache(ctx);
 
-        // draw sprites behind bg
-        for (uint8_t i = 0; i < 40; i++) {
-          if (
-            // sprite is below bg
-            ctx->gpu.oam_cache[i].priority &&
-
-            // sprite is on screen
-            BETWEEN(ctx->gpu.oam_cache[i].y, 0, 144) &&
-            BETWEEN(ctx->gpu.oam_cache[i].x, 0, 160) &&
-
-            // sprite is on current line
-            BETWEEN(ctx->gpu.line, ctx->gpu.oam_cache[i].y, ctx->gpu.oam_cache[i].y + 8)
-          ) {
-            const uint8_t max_j = MIN(8, 160 - ctx->gpu.oam_cache[i].x);
-
-            for (uint8_t j = 0; j < max_j; j++) {
-              const uint32_t ofs = 3 * (ctx->gpu.oam_cache[i].y * 160 + ctx->gpu.oam_cache[i].x + j);
-
-              // TODO: draw sprite scanline
-              ctx->gpu.fb[ofs + 0] = 0xff;
-              ctx->gpu.fb[ofs + 1] = 0xff;
-              ctx->gpu.fb[ofs + 2] = 0xff;
-            }
-          }
+        if (ctx->gpu.lcdc & (1 << 1)) {
+          // obj display is on, draw bg sprites
+          gpu_draw_objs(ctx, true);
         }
 
         if (ctx->gpu.lcdc & 1) {
+          // draw backgrond
           for (uint8_t i = 0; i < 160; i++) {
-            // get pixel color
+            // get bg pixel color
             const uint8_t c = bg_get_color(ctx, ctx->gpu.line, i);
 
             // populate framebuffer
@@ -10355,30 +10421,9 @@ templates:
           }
         }
 
-        // draw foreground sprites
-        for (uint8_t i = 0; i < 40; i++) {
-          if (
-            // sprite is above bg
-            !ctx->gpu.oam_cache[i].priority &&
-
-            // sprite is on screen
-            BETWEEN(ctx->gpu.oam_cache[i].y, 0, 144) &&
-            BETWEEN(ctx->gpu.oam_cache[i].x, 0, 160) &&
-
-            // sprite is on current line
-            BETWEEN(ctx->gpu.line, ctx->gpu.oam_cache[i].y, ctx->gpu.oam_cache[i].y + 8)
-          ) {
-            const uint8_t max_j = MIN(8, 160 - ctx->gpu.oam_cache[i].x);
-
-            for (int j = 0; j < max_j; j++) {
-              const uint32_t ofs = 3 * (ctx->gpu.oam_cache[i].y * 160 + ctx->gpu.oam_cache[i].x + j);
-
-              // TODO: draw sprite scanline
-              ctx->gpu.fb[ofs + 0] = 0xff;
-              ctx->gpu.fb[ofs + 1] = 0xff;
-              ctx->gpu.fb[ofs + 2] = 0xff;
-            }
-          }
+        if (ctx->gpu.lcdc & (1 << 1)) {
+          // obj display is on, draw fg sprites
+          gpu_draw_objs(ctx, false);
         }
       } else {
         // write blank line