That wasn't dead code, just another glitch. Fixes m3_wx_4_change_sprites

Core/display.c

@@ -17,7 +17,7 @@ static void fifo_clear(GB_fifo_t *fifo)
     fifo->read_end = fifo->size = 0;
 }
 
-static GB_fifo_item_t *fifo_pop(GB_fifo_t *fifo)
+static const GB_fifo_item_t *fifo_pop(GB_fifo_t *fifo)
 {
     assert(fifo->size);
     assert(fifo->size <= 8);
@@ -605,7 +605,13 @@ static void render_pixel_if_possible(GB_gameboy_t *gb)
     
     if (unlikely(!fifo_size(&gb->bg_fifo))) return;
     
-    fifo_item = fifo_pop(&gb->bg_fifo);
+    if (unlikely(gb->insert_bg_pixel)) {
+        gb->insert_bg_pixel = false;
+        fifo_item = ({static const GB_fifo_item_t empty_item = {0,}; &empty_item;});
+    }
+    else {
+        fifo_item = fifo_pop(&gb->bg_fifo);
+    }
     bg_priority = fifo_item->bg_priority;
     
     if (fifo_size(&gb->oam_fifo)) {
@@ -1753,6 +1759,13 @@ void GB_display_run(GB_gameboy_t *gb, unsigned cycles, bool force)
                     }
                 }
 
+                /* TODO: What happens when WX=0?*/
+                if (!GB_is_cgb(gb) && gb->wx_triggered && !gb->window_is_being_fetched &&
+                    gb->fetcher_state == 0 && gb->io_registers[GB_IO_WX] == (uint8_t) (gb->position_in_line + 7) && gb->bg_fifo.size == 8) {
+                    // Insert a pixel right at the FIFO's end
+                    gb->insert_bg_pixel = true;
+                }
+                
                 /* Handle objects */
                 /* When the object enabled bit is off, this proccess is skipped entirely on the DMG, but not on the CGB.
                    On the CGB, this bit is checked only when the pixel is actually popped from the FIFO. */

Core/gb.h

@@ -668,6 +668,7 @@ struct GB_gameboy_internal_s {
         bool delayed_glitch_hblank_interrupt;
         uint32_t frame_repeat_countdown;
         bool disable_window_pixel_insertion_glitch;
+        bool insert_bg_pixel;
     )
 
     /* Unsaved data. This includes all pointers, as well as everything that shouldn't be on a save state */