From 5c1cbedc034c59caba3955c663868c74e9631731 Mon Sep 17 00:00:00 2001
From: pjft <paulo.j.tavares@gmail.com>
Date: Sat, 6 May 2017 21:51:55 +0100
Subject: [PATCH] Adding enable/disable dithering core option with support for
 Neon GPU

---
 frontend/libretro.c                | 22 ++++++++++++++++++++++
 frontend/plugin_lib.h              |  1 +
 plugins/gpu_neon/psx_gpu/psx_gpu.h |  1 +
 plugins/gpu_neon/psx_gpu_if.c      | 14 ++++++++++++++
 plugins/gpulib/gpu.c               |  1 +
 plugins/gpulib/gpu.h               |  1 +
 6 files changed, 40 insertions(+)

diff --git a/frontend/libretro.c b/frontend/libretro.c
index c0784942..3013a7f4 100644
--- a/frontend/libretro.c
+++ b/frontend/libretro.c
@@ -456,6 +456,7 @@ void retro_set_environment(retro_environment_t cb)
       { "pcsx_rearmed_multitap1", "Multitap 1; auto|disabled|enabled" },
       { "pcsx_rearmed_multitap2", "Multitap 2; auto|disabled|enabled" },
       { "pcsx_rearmed_vibration", "Enable Vibration; enabled|disabled" },
+      { "pcsx_rearmed_dithering", "Enable Dithering; enabled|disabled" },
 #ifndef DRC_DISABLE
       { "pcsx_rearmed_drc", "Dynamic recompiler; enabled|disabled" },
 #endif
@@ -1376,6 +1377,27 @@ static void update_variables(bool in_flight)
          in_enable_vibration = 1;
    }
 
+   var.value = NULL;
+   var.key = "pcsx_rearmed_dithering";
+
+   if (environ_cb(RETRO_ENVIRONMENT_GET_VARIABLE, &var) || var.value)
+   {
+      if (strcmp(var.value, "disabled") == 0) {
+         pl_rearmed_cbs.gpu_peops.iUseDither = 0;
+         pl_rearmed_cbs.gpu_peopsgl.bDrawDither = 0;
+#ifdef __ARM_NEON__
+         pl_rearmed_cbs.gpu_neon.allow_dithering = 0;
+#endif
+      }
+      else if (strcmp(var.value, "enabled") == 0) {
+         pl_rearmed_cbs.gpu_peops.iUseDither = 1;
+         pl_rearmed_cbs.gpu_peopsgl.bDrawDither = 1;
+#ifdef __ARM_NEON__
+         pl_rearmed_cbs.gpu_neon.allow_dithering = 1;
+#endif
+      }
+   }
+
 #ifdef __ARM_NEON__
    var.value = "NULL";
    var.key = "pcsx_rearmed_neon_interlace_enable";
diff --git a/frontend/plugin_lib.h b/frontend/plugin_lib.h
index 83b27746..92e62e9d 100644
--- a/frontend/plugin_lib.h
+++ b/frontend/plugin_lib.h
@@ -71,6 +71,7 @@ struct rearmed_cbs {
 		int   allow_interlace; // 0 off, 1 on, 2 guess
 		int   enhancement_enable;
 		int   enhancement_no_main;
+		int   allow_dithering;
 	} gpu_neon;
 	struct {
 		int   iUseDither;
diff --git a/plugins/gpu_neon/psx_gpu/psx_gpu.h b/plugins/gpu_neon/psx_gpu/psx_gpu.h
index 1eaa99a4..1fa6b981 100644
--- a/plugins/gpu_neon/psx_gpu/psx_gpu.h
+++ b/plugins/gpu_neon/psx_gpu/psx_gpu.h
@@ -207,6 +207,7 @@ typedef struct
   u8 texture_4bpp_cache[32][256 * 256];
   u8 texture_8bpp_even_cache[16][256 * 256];
   u8 texture_8bpp_odd_cache[16][256 * 256];
+  int use_dithering;
 } psx_gpu_struct;
 
 typedef struct __attribute__((aligned(16)))
diff --git a/plugins/gpu_neon/psx_gpu_if.c b/plugins/gpu_neon/psx_gpu_if.c
index ad017614..788e3b42 100644
--- a/plugins/gpu_neon/psx_gpu_if.c
+++ b/plugins/gpu_neon/psx_gpu_if.c
@@ -184,4 +184,18 @@ void renderer_set_config(const struct rearmed_cbs *cbs)
     map_enhancement_buffer();
   if (cbs->pl_set_gpu_caps)
     cbs->pl_set_gpu_caps(GPU_CAP_SUPPORTS_2X);
+  
+  egpu.use_dithering = cbs->gpu_neon.allow_dithering;
+  if(!egpu.use_dithering) {
+    egpu.dither_table[0] = dither_table_row(0, 0, 0, 0);
+    egpu.dither_table[1] = dither_table_row(0, 0, 0, 0);
+    egpu.dither_table[2] = dither_table_row(0, 0, 0, 0);
+    egpu.dither_table[3] = dither_table_row(0, 0, 0, 0);
+  } else {
+    egpu.dither_table[0] = dither_table_row(-4, 0, -3, 1);
+    egpu.dither_table[1] = dither_table_row(2, -2, 3, -1);
+    egpu.dither_table[2] = dither_table_row(-3, 1, -4, 0);
+    egpu.dither_table[3] = dither_table_row(3, -1, 2, -2); 
+  }
+
 }
diff --git a/plugins/gpulib/gpu.c b/plugins/gpulib/gpu.c
index 125bd89b..9fc5f430 100644
--- a/plugins/gpulib/gpu.c
+++ b/plugins/gpulib/gpu.c
@@ -726,6 +726,7 @@ void GPUrearmedCallbacks(const struct rearmed_cbs *cbs)
   gpu.state.allow_interlace = cbs->gpu_neon.allow_interlace;
   gpu.state.enhancement_enable = cbs->gpu_neon.enhancement_enable;
 
+  gpu.useDithering = cbs->gpu_neon.allow_dithering;
   gpu.mmap = cbs->mmap;
   gpu.munmap = cbs->munmap;
 
diff --git a/plugins/gpulib/gpu.h b/plugins/gpulib/gpu.h
index d11f991c..7e1d18b5 100644
--- a/plugins/gpulib/gpu.h
+++ b/plugins/gpulib/gpu.h
@@ -88,6 +88,7 @@ struct psx_gpu {
     uint32_t last_flip_frame;
     uint32_t pending_fill[3];
   } frameskip;
+  int useDithering:1; /* 0 - off , 1 - on */
   uint16_t *(*get_enhancement_bufer)
     (int *x, int *y, int *w, int *h, int *vram_h);
   void *(*mmap)(unsigned int size);
-- 
2.39.2