From 9ba6915c85770ffb85b9e52d5dcfc4d4d79fe737 Mon Sep 17 00:00:00 2001
From: Lior Halphon <LIJI32@gmail.com>
Date: Tue, 16 Jul 2019 21:42:57 +0300
Subject: [PATCH] ICD JOYP write API

---
 Core/joypad.c | 17 ++++++++++++++++-
 Core/joypad.h |  1 +
 Core/memory.c |  2 +-
 3 files changed, 18 insertions(+), 2 deletions(-)

diff --git a/Core/joypad.c b/Core/joypad.c
index 4ae6e67..6c0eaff 100644
--- a/Core/joypad.c
+++ b/Core/joypad.c
@@ -3,6 +3,8 @@
 
 void GB_update_joyp(GB_gameboy_t *gb)
 {
+    if (gb->model & GB_MODEL_SGB_NO_SFC) return;
+    
     uint8_t key_selection = 0;
     uint8_t previous_state = 0;
 
@@ -53,14 +55,27 @@ void GB_update_joyp(GB_gameboy_t *gb)
             break;
     }
     
+    /* Todo: This assumes the keys *always* bounce, which is incorrect when emulating an SGB */
     if (previous_state != (gb->io_registers[GB_IO_JOYP] & 0xF)) {
-        /* The joypad interrupt DOES occur on CGB (Tested on CGB-CPU-06), unlike what some documents say. */
+        /* The joypad interrupt DOES occur on CGB (Tested on CGB-E), unlike what some documents say. */
         gb->io_registers[GB_IO_IF] |= 0x10;
     }
     
     gb->io_registers[GB_IO_JOYP] |= 0xC0;
 }
 
+void GB_icd_set_joyp(GB_gameboy_t *gb, uint8_t value)
+{
+    uint8_t previous_state = gb->io_registers[GB_IO_JOYP] & 0xF;
+    gb->io_registers[GB_IO_JOYP] &= 0xF0;
+    gb->io_registers[GB_IO_JOYP] |= value & 0xF;
+    
+    if (previous_state & ~(gb->io_registers[GB_IO_JOYP] & 0xF)) {
+        gb->io_registers[GB_IO_IF] |= 0x10;
+    }
+
+}
+
 void GB_set_key_state(GB_gameboy_t *gb, GB_key_t index, bool pressed)
 {
     assert(index >= 0 && index < GB_KEY_MAX);
diff --git a/Core/joypad.h b/Core/joypad.h
index 768d685..21fad53 100644
--- a/Core/joypad.h
+++ b/Core/joypad.h
@@ -17,6 +17,7 @@ typedef enum {
 
 void GB_set_key_state(GB_gameboy_t *gb, GB_key_t index, bool pressed);
 void GB_set_key_state_for_player(GB_gameboy_t *gb, GB_key_t index, unsigned player, bool pressed);
+void GB_icd_set_joyp(GB_gameboy_t *gb, uint8_t value);
 
 #ifdef GB_INTERNAL
 void GB_update_joyp(GB_gameboy_t *gb);
diff --git a/Core/memory.c b/Core/memory.c
index e5983cb..76d8821 100644
--- a/Core/memory.c
+++ b/Core/memory.c
@@ -741,8 +741,8 @@ static void write_high_memory(GB_gameboy_t *gb, uint16_t addr, uint8_t value)
                 return;
 
             case GB_IO_JOYP:
-                GB_sgb_write(gb, value);
                 gb->io_registers[GB_IO_JOYP] = value & 0xF0;
+                GB_sgb_write(gb, value);
                 GB_update_joyp(gb);
                 return;