From c6cf439511e83f2f157c5bcb064a76cb46dcaf33 Mon Sep 17 00:00:00 2001
From: Bruno Duarte Gouveia <bgouveia@gmail.com>
Date: Thu, 6 Jun 2019 22:00:16 +0100
Subject: [PATCH] VIDEO: sprite priority fixed for GBC handed differently
 (sprite index in oam is used instead of X position)

---
 sprite.v  | 4 +++-
 sprites.v | 4 ++++
 video.v   | 1 +
 3 files changed, 8 insertions(+), 1 deletion(-)

diff --git a/sprite.v b/sprite.v
index 6a3b285..ebfe74f 100644
--- a/sprite.v
+++ b/sprite.v
@@ -22,6 +22,8 @@
 module sprite (
 	input clk,
 	input size16,
+	input isGBC,
+	input [7:0] sprite_index,
 
 	input [7:0] v_cnt,
 	input [7:0] h_cnt,
@@ -50,7 +52,7 @@ module sprite (
 
 // x position for priority detection. Invisible sprites are far to the right and
 // have minimum priority
-assign x = v_visible?x_pos:8'hff;
+assign x = v_visible?isGBC?sprite_index:x_pos:8'hff;
 
 // register used to store pixel data for current line
 reg [7:0] data0;
diff --git a/sprites.v b/sprites.v
index a4fb3b2..9797c2c 100644
--- a/sprites.v
+++ b/sprites.v
@@ -23,6 +23,7 @@ module sprites (
 	input clk,
 	input clk_reg,
 	input size16,
+	input isGBC,
 
 	// pixel position input which the current pixel is generated for
 	input [7:0] v_cnt,
@@ -98,6 +99,9 @@ for(i=0;i<SPRITES;i=i+1) begin : spr
 	sprite sprite (
 		.clk      ( clk_reg ),
 		.size16   ( size16  ),
+		.isGBC    ( isGBC   ),
+		
+		.sprite_index ( i   ),
 
 		.v_cnt    ( v_cnt   ),
 		.h_cnt    ( h_cnt   ),
diff --git a/video.v b/video.v
index 0d56b2d..a569b7e 100644
--- a/video.v
+++ b/video.v
@@ -81,6 +81,7 @@ sprites sprites (
 	.clk      ( clk          ),
 	.clk_reg  ( clk_reg      ),
 	.size16   ( lcdc_spr_siz ),
+	.isGBC    ( isGBC        ),
 
 	.v_cnt    ( v_cnt        ),
 	.h_cnt    ( h_cnt-STAGE2 ),     // sprites are added in second stage