From 0f3f206b3c365b6afcb7e133e669371bddab02d1 Mon Sep 17 00:00:00 2001
From: bmaupin <bmaupin@users.noreply.github.com>
Date: Fri, 22 Nov 2019 13:08:21 -0500
Subject: [PATCH 1/2] Add option to change renderer

---
 platform/libretro/libretro.c              |  9 +++++++++
 platform/libretro/libretro_core_options.h | 11 +++++++++++
 2 files changed, 20 insertions(+)

diff --git a/platform/libretro/libretro.c b/platform/libretro/libretro.c
index b836185b..7d2e89bd 100644
--- a/platform/libretro/libretro.c
+++ b/platform/libretro/libretro.c
@@ -1431,6 +1431,15 @@ static void update_variables(void)
    if (environ_cb(RETRO_ENVIRONMENT_GET_VARIABLE, &var) && var.value) {
       PicoIn.sndFilterRange = (atoi(var.value) * 65536) / 100;
    }
+
+   var.value = NULL;
+   var.key = "picodrive_renderer";
+   if (environ_cb(RETRO_ENVIRONMENT_GET_VARIABLE, &var) && var.value) {
+      if (strcmp(var.value, "fast") == 0)
+         PicoIn.opt |= POPT_ALT_RENDERER;
+      else
+         PicoIn.opt &= ~POPT_ALT_RENDERER;
+   }
 }
 
 void retro_run(void)
diff --git a/platform/libretro/libretro_core_options.h b/platform/libretro/libretro_core_options.h
index a9ac83cb..4748b1e1 100644
--- a/platform/libretro/libretro_core_options.h
+++ b/platform/libretro/libretro_core_options.h
@@ -200,6 +200,17 @@ struct retro_core_option_definition option_defs_us[] = {
       },
       "60"
    },
+   {
+      "picodrive_renderer",
+      "Renderer",
+      "Fast renderer can't render any mid-frame image changes so it is useful only for some games.",
+      {
+         { "accurate", NULL },
+         { "fast",  NULL },
+         { NULL, NULL },
+      },
+      "accurate"
+   },
    { NULL, NULL, NULL, {{0}}, NULL },
 };
 

From 6877c461f60fb53d88d0368505202d57de053900 Mon Sep 17 00:00:00 2001
From: bmaupin <bmaupin@users.noreply.github.com>
Date: Tue, 25 Feb 2020 13:34:02 -0500
Subject: [PATCH 2/2] Copy tile-based fast renderer buffer

Also omit renderer option when RENDER_GSKIT_PS2 is used since it seems to have its own logic
---
 platform/libretro/libretro.c              | 19 +++++++++++++++++++
 platform/libretro/libretro_core_options.h |  2 ++
 2 files changed, 21 insertions(+)

diff --git a/platform/libretro/libretro.c b/platform/libretro/libretro.c
index 7d2e89bd..0216d2b5 100644
--- a/platform/libretro/libretro.c
+++ b/platform/libretro/libretro.c
@@ -1545,6 +1545,25 @@ void retro_run(void)
    ps2->padding = padding;
 
 #else
+   if (PicoIn.opt & POPT_ALT_RENDERER) {
+      /* In retro_init, PicoDrawSetOutBuf is called to make sure the output gets written to vout_buf, but this only
+       * applies to the line renderer (pico/draw.c). The faster tile-based renderer (pico/draw2.c) enabled by
+       * POPT_ALT_RENDERER writes to Pico.est.Draw2FB, so we need to manually copy that to vout_buf.
+       */
+      /* This section is mostly copied from pemu_finalize_frame in platform/linux/emu.c */
+      unsigned short *pd = (unsigned short *)vout_buf;
+      /* Skip the leftmost 8 columns (it seems to be used as some sort of caching or overscan area) */
+      unsigned char *ps = Pico.est.Draw2FB + 8;
+      unsigned short *pal = Pico.est.HighPal;
+      int x;
+      if (Pico.m.dirtyPal)
+         PicoDrawUpdateHighPal();
+      /* Copy up to the max height to include the overscan area, and skip the leftmost 8 columns again */
+      for (i = 0; i < VOUT_MAX_HEIGHT; i++, ps += 8)
+         for (x = 0; x < vout_width; x++)
+            *pd++ = pal[*ps++];
+   }
+
    buff = (char*)vout_buf + vout_offset;
 #endif
 
diff --git a/platform/libretro/libretro_core_options.h b/platform/libretro/libretro_core_options.h
index 4748b1e1..bb69909a 100644
--- a/platform/libretro/libretro_core_options.h
+++ b/platform/libretro/libretro_core_options.h
@@ -200,6 +200,7 @@ struct retro_core_option_definition option_defs_us[] = {
       },
       "60"
    },
+#if !defined(RENDER_GSKIT_PS2)
    {
       "picodrive_renderer",
       "Renderer",
@@ -211,6 +212,7 @@ struct retro_core_option_definition option_defs_us[] = {
       },
       "accurate"
    },
+#endif
    { NULL, NULL, NULL, {{0}}, NULL },
 };