From 0c716bd970540e57c35868eec6e33b2ad96e3ee6 Mon Sep 17 00:00:00 2001
From: Lior Halphon <LIJI32@gmail.com>
Date: Thu, 27 Feb 2020 22:49:34 +0200
Subject: [PATCH] More accurate timing emulation of window-objects interaction

---
 Core/display.c | 50 +++++++++++++++++++++++++++++++-------------------
 1 file changed, 31 insertions(+), 19 deletions(-)

diff --git a/Core/display.c b/Core/display.c
index 256d981..b4455fd 100644
--- a/Core/display.c
+++ b/Core/display.c
@@ -729,6 +729,7 @@ void GB_display_run(GB_gameboy_t *gb, uint8_t cycles)
         return;
     }
     GB_object_t *objects = (GB_object_t *) &gb->oam;
+    bool window_got_activated = false;
     
     GB_STATE_MACHINE(gb, display, cycles, 2) {
         GB_STATE(gb, display, 1);
@@ -771,6 +772,7 @@ void GB_display_run(GB_gameboy_t *gb, uint8_t cycles)
         GB_STATE(gb, display, 39);
         GB_STATE(gb, display, 40);
         GB_STATE(gb, display, 41);
+        GB_STATE(gb, display, 42);
 
     }
     
@@ -948,6 +950,26 @@ void GB_display_run(GB_gameboy_t *gb, uint8_t cycles)
             gb->bg_fifo_paused = false;
             gb->oam_fifo_paused = false;
             while (true) {
+                /* Handle window */
+                /* Todo: verify timings */
+                if (!gb->wx_triggered && gb->wy_triggered && (gb->io_registers[GB_IO_LCDC] & 0x20)) {
+                    if (gb->io_registers[GB_IO_WX] >= 167) {
+                        // Too late to enable the window
+                    }
+                    else if (gb->io_registers[GB_IO_WX] == (uint8_t) (gb->position_in_line + 7) ||
+                             (gb->io_registers[GB_IO_WX] == (uint8_t) (gb->position_in_line + 6) && !gb->wx_just_changed)) {
+                        gb->window_y++;
+                        if (gb->io_registers[GB_IO_WX] != 166) {
+                            gb->wx_triggered = true;
+                            fifo_clear(&gb->bg_fifo);
+                            gb->bg_fifo_paused = true;
+                            gb->oam_fifo_paused = true;
+                            gb->fetcher_state = 1;
+                            window_got_activated = true;
+                        }
+                    }
+                }
+
                 /* Handle objects */
                 /* When the sprite 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. */
@@ -962,6 +984,15 @@ void GB_display_run(GB_gameboy_t *gb, uint8_t cycles)
                 while (gb->n_visible_objs != 0 &&
                        (gb->io_registers[GB_IO_LCDC] & 2 || GB_is_cgb(gb)) &&
                        gb->obj_comparators[gb->n_visible_objs - 1] == (uint8_t)(gb->position_in_line + 8)) {
+                    
+                    /* TODO: This is wrong. It is only correct for a single object, not for more than one. */
+                    if (window_got_activated) {
+                        window_got_activated = false;
+                        gb->fetcher_state = 0;
+                        gb->cycles_for_line += 6;
+                        GB_SLEEP(gb, display, 42, 6);
+                    }
+                    
                     while (gb->fetcher_state < 5) {
                         advance_fetcher_state_machine(gb);
                         gb->cycles_for_line++;
@@ -1035,25 +1066,6 @@ abort_fetching_object:
                 gb->object_fetch_aborted = false;
                 gb->during_object_fetch = false;
                 
-                /* Handle window */
-                /* Todo: verify timings */
-                if (!gb->wx_triggered && gb->wy_triggered && (gb->io_registers[GB_IO_LCDC] & 0x20)) {
-                    if (gb->io_registers[GB_IO_WX] >= 167) {
-                        // Too late to enable the window
-                    }
-                    else if (gb->io_registers[GB_IO_WX] == (uint8_t) (gb->position_in_line + 7) ||
-                               (gb->io_registers[GB_IO_WX] == (uint8_t) (gb->position_in_line + 6) && !gb->wx_just_changed)) {
-                        gb->window_y++;
-                        if (gb->io_registers[GB_IO_WX] != 166) {
-                            gb->wx_triggered = true;
-                            fifo_clear(&gb->bg_fifo);
-                            gb->bg_fifo_paused = true;
-                            gb->oam_fifo_paused = true;
-                            gb->fetcher_state = 1;
-                        }
-                    }
-                }
-                
                 render_pixel_if_possible(gb);
                 advance_fetcher_state_machine(gb);