From 9bde98dede40e5062670353b66d8c64baeb94e34 Mon Sep 17 00:00:00 2001
From: Lior Halphon <LIJI32@gmail.com>
Date: Mon, 4 Sep 2017 00:16:12 +0300
Subject: [PATCH] SCY latching is now correctly emulated, rendering mode timing
refined.
---
Core/display.c | 10 +++++++---
Core/gb.h | 1 +
2 files changed, 8 insertions(+), 3 deletions(-)
diff --git a/Core/display.c b/Core/display.c
index 15d8d260..4def6c89 100755
--- a/Core/display.c
+++ b/Core/display.c
@@ -133,7 +133,7 @@ static uint32_t get_pixel(GB_gameboy_t *gb, uint8_t x, uint8_t y)
}
else {
x += gb->effective_scx;
- y += gb->io_registers[GB_IO_SCY];
+ y += gb->effective_scy;
}
if (gb->io_registers[GB_IO_LCDC] & 0x08 && !in_window) {
map = 0x1C00;
@@ -619,13 +619,17 @@ void GB_display_run(GB_gameboy_t *gb, uint8_t cycles)
/* Render */
- /* Todo: it appears that the actual rendering starts 4 cycles after mode 3 starts. Is this correct? */
- int16_t current_lcdc_x = gb->display_cycles % LINE_LENGTH - MODE2_LENGTH - (gb->effective_scx & 0x7) - 4;
+ int16_t current_lcdc_x = gb->display_cycles % LINE_LENGTH - MODE2_LENGTH - (gb->effective_scx & 0x7) - 7;
for (;gb->previous_lcdc_x < current_lcdc_x; gb->previous_lcdc_x++) {
if (gb->previous_lcdc_x >= WIDTH) {
continue;
}
+
+ if (((gb->previous_lcdc_x + gb->effective_scx) & 7) == 0) {
+ gb->effective_scy = gb->io_registers[GB_IO_SCY];
+ }
+
if (gb->previous_lcdc_x < 0) {
continue;
}
diff --git a/Core/gb.h b/Core/gb.h
index a9297626..37562561 100644
--- a/Core/gb.h
+++ b/Core/gb.h
@@ -385,6 +385,7 @@ struct GB_gameboy_internal_s {
bool oam_write_blocked;
bool vram_write_blocked;
bool window_disabled_while_active;
+ uint8_t effective_scy; // SCY is latched when starting to draw a tile
);
/* Unsaved data. This includes all pointers, as well as everything that shouldn't be on a save state */