From 89cfdb4d650db3d71cb81baa993aad8537fcfe4d Mon Sep 17 00:00:00 2001
From: Samuel Walker <swalker@piwalker.net>
Date: Wed, 19 Feb 2025 10:20:45 -0700
Subject: [PATCH] ppu work

---
 lib/emu.c          |  6 +++---
 lib/lcd.c          |  2 +-
 lib/ppu.c          | 30 ++++++++++++++++--------------
 lib/ppu_pipeline.c | 23 +++++++++++++++++++++--
 lib/ui.c           |  3 ++-
 5 files changed, 43 insertions(+), 21 deletions(-)

diff --git a/lib/emu.c b/lib/emu.c
index 2aec343..73edba0 100644
--- a/lib/emu.c
+++ b/lib/emu.c
@@ -93,10 +93,10 @@ int emu_run(int argc, char **argv) {
     while(!ctx.die) {
         sleep_ms(1);
         ui_handle_events();
-        if (prev_frame != ppu_get_context()->current_frame) {
+        //if (prev_frame != ppu_get_context()->current_frame) {
             ui_update();
-        }
-        prev_frame = ppu_get_context()->current_frame;
+        //}
+        //prev_frame = ppu_get_context()->current_frame;
     }
     
 
diff --git a/lib/lcd.c b/lib/lcd.c
index 64f64d3..5e4c80a 100644
--- a/lib/lcd.c
+++ b/lib/lcd.c
@@ -4,7 +4,7 @@
 
 static lcd_context ctx;
 
-static unsigned long colors_default[4] = {0xFFFFFFFF, 0xFFAAAAAA, 0xFF555555, 0xFF000000};
+static unsigned long colors_default[4] = {0xFF759833, 0xFF588F51, 0xFF3B7560, 0xFF2E615A};
 
 lcd_context *lcd_get_context() {
     return &ctx;
diff --git a/lib/ppu.c b/lib/ppu.c
index 552ec35..d1ae9f8 100644
--- a/lib/ppu.c
+++ b/lib/ppu.c
@@ -40,21 +40,23 @@ void ppu_init() {
 }
 
 void ppu_tick() {
-    ctx.line_ticks++;
+    if(LCDC_LCD_ENABLE){
+        ctx.line_ticks++;
 
-    switch(LCDS_MODE) {
-        case MODE_OAM:
-            ppu_mode_oam();
-            break;
-        case MODE_XFER:
-            ppu_mode_xfer();
-            break;
-        case MODE_VBLANK:
-            ppu_mode_vblank();
-            break;
-        case MODE_HBLANK:
-            ppu_mode_hblank();
-            break;
+        switch(LCDS_MODE) {
+            case MODE_OAM:
+                ppu_mode_oam();
+                break;
+            case MODE_XFER:
+                ppu_mode_xfer();
+                break;
+            case MODE_VBLANK:
+                ppu_mode_vblank();
+                break;
+            case MODE_HBLANK:
+                ppu_mode_hblank();
+                break;
+        }
     }
 }
 
diff --git a/lib/ppu_pipeline.c b/lib/ppu_pipeline.c
index c80f0b8..8a214d8 100644
--- a/lib/ppu_pipeline.c
+++ b/lib/ppu_pipeline.c
@@ -255,6 +255,23 @@ void pipeline_fifo_reset() {
     ppu_get_context()->pfc.pixel_fifo.head = 0;
 }
 
+//Rate at wich the screen interpolates between the old and new colors
+//Used to simulate the slow response time of the GB's LCD
+//A value of zero will always use the exiting screen color, while a 1 will always use the new color
+//any value in between will interpolate that percentage between the two
+#define INTERPOLATION_RATE 0.5
+
+u32 interpolate(u32 first, u32 second) {
+    u32 final = 0;
+    for(int c = 0; c < 4; c++) {
+        u8 c1 = (first >> (c*8)) & 0xFF;
+        u8 c2 = (second >> (c*8)) & 0xFF;
+        u8 cf = (u8)(((((float)c2/(float)0xFF) - ((float)c1/(float)0xFF)) * INTERPOLATION_RATE + ((float)c1/(float)0xFF)) * 0xFF);
+        final |= cf << (c*8);
+    }
+    return final;
+}
+
 void pipeline_push_pixel() {
     if (ppu_get_context()->pfc.pixel_fifo.size > 8) {
         u32 pixel_data = pixel_fifo_pop();
@@ -270,13 +287,15 @@ void pipeline_push_pixel() {
         }
         if(ppu_get_context()->rendering_window) {
                 ppu_get_context()->video_buffer[ppu_get_context()->pfc.pushed_x +
-                    (lcd_get_context()->ly * XRES)] = pixel_data;
+                    (lcd_get_context()->ly * XRES)] = interpolate(ppu_get_context()->video_buffer[ppu_get_context()->pfc.pushed_x +
+                        (lcd_get_context()->ly * XRES)], pixel_data);
 
                 ppu_get_context()->pfc.pushed_x++;
         }else {
             if(ppu_get_context()->pfc.line_x >= (lcd_get_context()->scroll_x % 8)) {
                 ppu_get_context()->video_buffer[ppu_get_context()->pfc.pushed_x +
-                    (lcd_get_context()->ly * XRES)] = pixel_data;
+                    (lcd_get_context()->ly * XRES)] = interpolate(ppu_get_context()->video_buffer[ppu_get_context()->pfc.pushed_x +
+                        (lcd_get_context()->ly * XRES)], pixel_data);
 
                     ppu_get_context()->pfc.pushed_x++;
             }
diff --git a/lib/ui.c b/lib/ui.c
index 573d633..14f46c5 100644
--- a/lib/ui.c
+++ b/lib/ui.c
@@ -5,6 +5,7 @@
 #include <bus.h>
 #include <audio.h>
 #include <string.h>
+#include <lcd.h>
 
 #include <SDL.h>
 #include <SDL_ttf.h>
@@ -58,7 +59,7 @@ void ui_init(){
     SDL_SetWindowPosition(sdlDebugWindow, x+SCREEN_WIDTH, y);
 }
 
-static unsigned long tile_colors[4] = {0xFFFFFFFF, 0xFFAAAAAA, 0xFF555555, 0xFF000000};
+static unsigned long tile_colors[4] = {0xFF759833, 0xFF588F51, 0xFF3B7560, 0xFF2E615A};
 
 void display_tile(SDL_Surface *surface, u16 startLocation, u16 tileNum, int x, int y) {
     SDL_Rect rc;