From 955860b4631d4dac7393c0317b6fd22d42fad391 Mon Sep 17 00:00:00 2001
From: Lior Halphon <LIJI32@gmail.com>
Date: Fri, 28 Feb 2020 22:36:51 +0200
Subject: [PATCH] Get rid of the FIFO pause flags

---
 Core/display.c | 26 ++++++++++----------------
 Core/gb.h      |  6 +++---
 2 files changed, 13 insertions(+), 19 deletions(-)

diff --git a/Core/display.c b/Core/display.c
index 9aaf40b..85fc858 100644
--- a/Core/display.c
+++ b/Core/display.c
@@ -422,20 +422,21 @@ static void render_pixel_if_possible(GB_gameboy_t *gb)
     bool draw_oam = false;
     bool bg_enabled = true, bg_priority = false;
     
-    if (!gb->bg_fifo_paused) {
+    if (fifo_size(&gb->bg_fifo)) {
         fifo_item = fifo_pop(&gb->bg_fifo);
         bg_priority = fifo_item->bg_priority;
-    }
-    
-    if (!gb->oam_fifo_paused && fifo_size(&gb->oam_fifo)) {
-        oam_fifo_item = fifo_pop(&gb->oam_fifo);
-        if (oam_fifo_item->pixel && (gb->io_registers[GB_IO_LCDC] & 2)) {
-            draw_oam = true;
-            bg_priority |= oam_fifo_item->bg_priority;
+        
+        if (fifo_size(&gb->oam_fifo)) {
+            oam_fifo_item = fifo_pop(&gb->oam_fifo);
+            if (oam_fifo_item->pixel && (gb->io_registers[GB_IO_LCDC] & 2)) {
+                draw_oam = true;
+                bg_priority |= oam_fifo_item->bg_priority;
+            }
         }
     }
     
-    if (gb->bg_fifo_paused) return;
+
+    if (!fifo_item) return;
 
     /* Drop pixels for scrollings */
     if (gb->position_in_line >= 160 || (gb->disable_rendering && !gb->sgb)) {
@@ -658,7 +659,6 @@ static void advance_fetcher_state_machine(GB_gameboy_t *gb)
         gb->fetcher_state++;
         // fallthrough
             
-            
         case GB_FETCHER_PUSH: {
             if (fifo_size(&gb->bg_fifo) > 0) break;
             
@@ -673,8 +673,6 @@ static void advance_fetcher_state_machine(GB_gameboy_t *gb)
             
             fifo_push_bg_row(&gb->bg_fifo, gb->current_tile_data[0], gb->current_tile_data[1],
                              gb->current_tile_attributes & 7, gb->current_tile_attributes & 0x80, gb->current_tile_attributes & 0x20);
-            gb->bg_fifo_paused = false;
-            gb->oam_fifo_paused = false;
             gb->fetcher_state = 0;
         }
         break;
@@ -946,8 +944,6 @@ void GB_display_run(GB_gameboy_t *gb, uint8_t cycles)
             
             /* The actual rendering cycle */
             gb->fetcher_state = 0;
-            gb->bg_fifo_paused = false;
-            gb->oam_fifo_paused = false;
             while (true) {
                 /* Handle window */
                 /* Todo: verify timings */
@@ -962,8 +958,6 @@ void GB_display_run(GB_gameboy_t *gb, uint8_t cycles)
                             gb->wx_triggered = true;
                             gb->window_tile_x = 0;
                             fifo_clear(&gb->bg_fifo);
-                            gb->bg_fifo_paused = true;
-                            gb->oam_fifo_paused = true;
                             gb->fetcher_state = 0;
                             window_got_activated = true;
                         }
diff --git a/Core/gb.h b/Core/gb.h
index b8cbd97..65cfb4c 100644
--- a/Core/gb.h
+++ b/Core/gb.h
@@ -489,7 +489,7 @@ struct GB_gameboy_internal_s {
         bool vram_read_blocked;
         bool oam_write_blocked;
         bool vram_write_blocked;
-        GB_PADDING(bool, window_disabled_while_active);
+        bool fifo_insertion_glitch;
         uint8_t current_line;
         uint16_t ly_for_comparison;
         GB_fifo_t bg_fifo, oam_fifo;
@@ -500,8 +500,8 @@ struct GB_gameboy_internal_s {
         uint8_t current_tile_attributes;
         uint8_t current_tile_data[2];
         uint8_t fetcher_state;
-        bool bg_fifo_paused;
-        bool oam_fifo_paused;
+        GB_PADDING(bool,bg_fifo_paused);
+        GB_PADDING(bool,oam_fifo_paused);
         bool wx_triggered;
         uint8_t visible_objs[10];
         uint8_t obj_comparators[10];