From 30bc1bb371c8ee36616e317f90f7c96e6153d398 Mon Sep 17 00:00:00 2001
From: neonloop
Date: Fri, 27 Aug 2021 17:04:48 +0000
Subject: Adds "fastest" ghosting option to gambatte

---
 patches/gambatte/0001-ghosting-fastest.patch | 107 +++++++++++++++++++++++++++
 1 file changed, 107 insertions(+)
 create mode 100644 patches/gambatte/0001-ghosting-fastest.patch

(limited to 'patches')

diff --git a/patches/gambatte/0001-ghosting-fastest.patch b/patches/gambatte/0001-ghosting-fastest.patch
new file mode 100644
index 0000000..a4581f7
--- /dev/null
+++ b/patches/gambatte/0001-ghosting-fastest.patch
@@ -0,0 +1,107 @@
+diff --git a/libgambatte/libretro/libretro.cpp b/libgambatte/libretro/libretro.cpp
+index 61a2949..8f0e0aa 100644
+--- a/libgambatte/libretro/libretro.cpp
++++ b/libgambatte/libretro/libretro.cpp
+@@ -123,7 +123,8 @@ enum frame_blend_method
+    FRAME_BLEND_NONE = 0,
+    FRAME_BLEND_MIX,
+    FRAME_BLEND_LCD_GHOSTING,
+-   FRAME_BLEND_LCD_GHOSTING_FAST
++   FRAME_BLEND_LCD_GHOSTING_FAST,
++   FRAME_BLEND_LCD_GHOSTING_FASTEST
+ };
+ 
+ static enum frame_blend_method frame_blend_type  = FRAME_BLEND_NONE;
+@@ -177,6 +178,41 @@ static void blend_frames_mix(void)
+    }
+ }
+ 
++/* Same as blend_frames_mix, but blending already blended frames to
++ * simulate lcd response */
++static void blend_frames_lcd_ghost_fastest(void)
++{
++   gambatte::video_pixel_t *curr = video_buf;
++   gambatte::video_pixel_t *prev = video_buf_prev_1;
++   size_t x, y;
++
++   for (y = 0; y < VIDEO_HEIGHT; y++)
++   {
++      for (x = 0; x < VIDEO_WIDTH; x++)
++      {
++         /* Get colours from current + previous frames */
++         gambatte::video_pixel_t rgb_curr = *(curr + x);
++         gambatte::video_pixel_t rgb_prev = *(prev + x);
++
++         /* Mix colours
++          * > "Mixing Packed RGB Pixels Efficiently"
++          *   http://blargg.8bitalley.com/info/rgb_mixing.html */
++#ifdef VIDEO_RGB565
++         *(curr + x) = (rgb_curr + rgb_prev + ((rgb_curr ^ rgb_prev) & 0x821)) >> 1;
++#elif defined(VIDEO_ABGR1555)
++         *(curr + x) = (rgb_curr + rgb_prev + ((rgb_curr ^ rgb_prev) & 0x521)) >> 1;
++#else
++         *(curr + x) = (rgb_curr + rgb_prev + ((rgb_curr ^ rgb_prev) & 0x10101)) >> 1;
++#endif
++         /* Store colours for next frame */
++         *(prev + x) = rgb_prev == *(curr + x) ? rgb_curr : *(curr + x);
++      }
++
++      curr += VIDEO_PITCH;
++      prev += VIDEO_PITCH;
++   }
++}
++
+ static void blend_frames_lcd_ghost(void)
+ {
+    gambatte::video_pixel_t *curr   = video_buf;
+@@ -451,6 +487,11 @@ static void init_frame_blending(void)
+          if (!allocate_video_buf_acc())
+             return;
+          break;
++      case FRAME_BLEND_LCD_GHOSTING_FASTEST:
++         /* Fastest ghosting requires a single accumulator buffer */
++         if (!allocate_video_buf_prev(&video_buf_prev_1))
++            return;
++         break;
+       case FRAME_BLEND_NONE:
+       default:
+          /* Error condition - cannot happen
+@@ -494,6 +535,9 @@ static void init_frame_blending(void)
+       case FRAME_BLEND_LCD_GHOSTING_FAST:
+          blend_frames = blend_frames_lcd_ghost_fast;
+          return;
++      case FRAME_BLEND_LCD_GHOSTING_FASTEST:
++         blend_frames = blend_frames_lcd_ghost_fastest;
++         return;
+       case FRAME_BLEND_NONE:
+       default:
+          /* Error condition - cannot happen
+@@ -568,6 +612,8 @@ static void check_frame_blend_variable(void)
+          frame_blend_type = FRAME_BLEND_LCD_GHOSTING;
+       else if (!strcmp(var.value, "lcd_ghosting_fast"))
+          frame_blend_type = FRAME_BLEND_LCD_GHOSTING_FAST;
++      else if (!strcmp(var.value, "lcd_ghosting_fastest"))
++         frame_blend_type = FRAME_BLEND_LCD_GHOSTING_FASTEST;
+    }
+ 
+    if (frame_blend_type == FRAME_BLEND_NONE)
+diff --git a/libgambatte/libretro/libretro_core_options.h b/libgambatte/libretro/libretro_core_options.h
+index ca5d896..e76c29f 100644
+--- a/libgambatte/libretro/libretro_core_options.h
++++ b/libgambatte/libretro/libretro_core_options.h
+@@ -471,10 +471,11 @@ struct retro_core_option_v2_definition option_defs_us[] = {
+       NULL,
+       NULL,
+       {
+-         { "disabled",          NULL },
+-         { "mix",               "Simple" },
+-         { "lcd_ghosting",      "LCD Ghosting (Accurate)" },
+-         { "lcd_ghosting_fast", "LCD Ghosting (Fast)" },
++         { "disabled",             NULL },
++         { "mix",                  "Simple" },
++         { "lcd_ghosting",         "LCD Ghosting (Accurate)" },
++         { "lcd_ghosting_fast",    "LCD Ghosting (Fast)" },
++         { "lcd_ghosting_fastest", "LCD Ghosting (Fastest)" },
+          { NULL, NULL },
+       },
+       "disabled"
-- 
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