From b9d24e00470c2538aa55e36833a7b89cdfcd9494 Mon Sep 17 00:00:00 2001
From: Paul Duncan <pabs@pablotron.org>
Date: Wed, 20 Jun 2018 22:41:50 -0400
Subject: populate gpu_draw()

---
 ops.yaml | 77 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++--
 1 file changed, 75 insertions(+), 2 deletions(-)

(limited to 'ops.yaml')

diff --git a/ops.yaml b/ops.yaml
index 0b6a42e..30c0c64 100644
--- a/ops.yaml
+++ b/ops.yaml
@@ -7523,6 +7523,7 @@ templates:
     #include "gb.h"
 
     #define UNUSED(a) ((void) (a))
+    #define MIN(a, b) (((a) < (b)) ? (a) : (b))
 
     #define FLAG(ctx, f) (cpu_rb(ctx, RB_F) & (F_##f))
     #define F_Z (1 << 7)
@@ -9387,8 +9388,80 @@ templates:
     gpu_draw(
       gb_t * const ctx
     ) {
-      UNUSED(ctx);
-      // TODO
+      struct {
+        uint8_t x, y, tile;
+        bool priority,
+             y_flip,
+             x_flip,
+             palette;
+      } objs[40];
+
+      // decode oam
+      for (int i = 0; i < 40; i++) {
+        objs[i].y = (ctx->mmu.oam[i * 4 + 0] + 16) & 0xFF;
+        objs[i].x = (ctx->mmu.oam[i * 4 + 1] + 8) & 0xFF;
+        objs[i].tile = ctx->mmu.oam[i * 4 + 2];
+
+        const uint8_t flags = ctx->mmu.oam[i * 4 + 3];
+        objs[i].priority = flags & (1 << 7);
+        objs[i].y_flip = flags & (1 << 6);
+        objs[i].x_flip = flags & (1 << 5);
+        objs[i].palette = flags & (1 << 4);
+      }
+
+      // draw sprites behind bg
+      for (int i = 0; i < 40; i++) {
+        if (
+          // sprite is below bg
+          objs[i].priority &&
+
+          // sprite is on screen
+          objs[i].y < 144 && objs[i].x < 160 &&
+
+          // sprite is on current line
+          ctx->gpu.line >= objs[i].y &&
+          ctx->gpu.line <= objs[i].y
+        ) {
+          const uint8_t max_j = MIN(8, 160 - objs[i].x);
+
+          for (uint8_t j = 0; j < max_j; j++) {
+            const uint32_t ofs = 3 * (objs[i].y * 160 + objs[i].x + j);
+
+            // TODO: draw sprite scanline
+            ctx->gpu.rgb[ofs + 0] = 0xff;
+            ctx->gpu.rgb[ofs + 1] = 0xff;
+            ctx->gpu.rgb[ofs + 2] = 0xff;
+          }
+        }
+      }
+
+      // TODO: draw background
+
+      // draw foreground sprites
+      for (int i = 0; i < 40; i++) {
+        if (
+          // sprite is above bg
+          !objs[i].priority &&
+
+          // sprite is on screen
+          objs[i].y < 144 && objs[i].x < 160 &&
+
+          // sprite is on current line
+          ctx->gpu.line >= objs[i].y &&
+          ctx->gpu.line <= objs[i].y
+        ) {
+          const uint8_t max_j = MIN(8, 160 - objs[i].x);
+
+          for (int j = 0; j < max_j; j++) {
+            const uint32_t ofs = 3 * (objs[i].y * 160 + objs[i].x + j);
+
+            // TODO: draw sprite scanline
+            ctx->gpu.rgb[ofs + 0] = 0xff;
+            ctx->gpu.rgb[ofs + 1] = 0xff;
+            ctx->gpu.rgb[ofs + 2] = 0xff;
+          }
+        }
+      }
     }
 
     static void
-- 
cgit v1.2.3