From c057cb5ed6ffed8a9b88158a9e0e77608b46813f Mon Sep 17 00:00:00 2001
From: neonloop
Date: Thu, 11 Mar 2021 16:29:10 +0000
Subject: Adds NO_HIRES to scale hires mode to low-res screens

---
 source/gfx.c | 55 +++++++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 55 insertions(+)

diff --git a/source/gfx.c b/source/gfx.c
index 3508011..0cf0ac8 100644
--- a/source/gfx.c
+++ b/source/gfx.c
@@ -220,8 +220,13 @@ bool S9xInitGFX(void)
    DrawTilePtr = DrawTile16;
    DrawClippedTilePtr = DrawClippedTile16;
    DrawLargePixelPtr = DrawLargePixel16;
+#ifdef NO_HIRES
+   DrawHiResTilePtr = DrawTile16HalfWidth;
+   DrawHiResClippedTilePtr = DrawClippedTile16HalfWidth;
+#else
    DrawHiResTilePtr = DrawTile16;
    DrawHiResClippedTilePtr = DrawClippedTile16;
+#endif
    GFX.PPL = GFX.Pitch >> 1;
    GFX.PPLx2 = GFX.Pitch;
    S9xFixColourBrightness();
@@ -292,6 +297,16 @@ void S9xStartScreenRefresh(void)
 
       if (PPU.BGMode == 5 || PPU.BGMode == 6)
          IPPU.Interlace = (Memory.FillRAM[0x2133] & 1);
+#ifdef NO_HIRES
+      if (PPU.BGMode == 5 || PPU.BGMode == 6 || IPPU.Interlace)
+      {
+         IPPU.RenderedScreenWidth = 256;
+         IPPU.DoubleWidthPixels = false;
+         // Secret of Mana displays menus with mode 5.
+         // Make them readable.
+         IPPU.HalfWidthPixels = true;
+      }
+#else
       if (PPU.BGMode == 5 || PPU.BGMode == 6 || IPPU.Interlace)
       {
          IPPU.RenderedScreenWidth = 512;
@@ -315,6 +330,7 @@ void S9xStartScreenRefresh(void)
             GFX.PPLx2 = GFX.PPL << 1;
          }
       }
+#endif
       else
       {
          IPPU.RenderedScreenWidth = 256;
@@ -755,6 +771,18 @@ static void DrawOBJS(bool OnMain, uint8_t D)
       }
    }
 
+#ifdef NO_HIRES
+   if (PPU.BGMode == 5 || PPU.BGMode == 6)
+   {
+      // Bah, OnMain is never used except to determine if calling
+      // SelectTileRenderer is necessary. So let's hack it to false here
+      // to stop SelectTileRenderer from being called when it causes
+      // problems.
+      OnMain = false;
+   }
+   DrawTilePtr = DrawTile16;
+   DrawClippedTilePtr = DrawClippedTile16;
+#else
    if (PPU.BGMode == 5 || PPU.BGMode == 6)
    {
       /* Bah, OnMain is never used except to determine if calling
@@ -779,6 +807,7 @@ static void DrawOBJS(bool OnMain, uint8_t D)
       DrawTilePtr = DrawTile16;
       DrawClippedTilePtr = DrawClippedTile16;
    }
+#endif
 
    GFX.Z1 = D + 2;
 
@@ -1651,6 +1680,9 @@ static void DrawBackground(uint32_t BGMode, uint32_t bg, uint8_t Z1, uint8_t Z2)
 
       case 5:
       case 6: /* XXX: is also offset per tile. */
+#ifdef NO_HIRES
+         SelectTileRenderer(true /* normal */);
+#endif
          DrawBackgroundMode5(bg, Z1, Z2);
          return;
    }
@@ -2668,6 +2700,26 @@ void S9xUpdateScreen(void)
    starty = GFX.StartY;
    endy   = GFX.EndY;
 
+#ifdef NO_HIRES
+   if (PPU.BGMode == 5 || PPU.BGMode == 6 || IPPU.Interlace)
+   {
+      if (!IPPU.HalfWidthPixels)
+      {
+         // The game has switched from lo-res to hi-res mode part way down
+         // the screen. Hi-res pixels must now be drawn at half width.
+         IPPU.HalfWidthPixels = true;
+      }
+   }
+   else
+   {
+      if (IPPU.HalfWidthPixels)
+      {
+         // The game has switched from hi-res to lo-res mode part way down
+         // the screen. Lo-res pixels must now be drawn at FULL width.
+         IPPU.HalfWidthPixels = false;
+      }
+   }
+#else
    if (PPU.BGMode == 5 || PPU.BGMode == 6 || IPPU.Interlace || IPPU.DoubleHeightPixels)
    {
       if (PPU.BGMode == 5 || PPU.BGMode == 6 || IPPU.Interlace)
@@ -2725,6 +2777,7 @@ void S9xUpdateScreen(void)
          }
       }
    }
+#endif
 
    black = BLACK | (BLACK << 16);
 
@@ -3132,6 +3185,7 @@ void S9xUpdateScreen(void)
       }
    }
 
+#ifndef NO_HIRES
    if (PPU.BGMode != 5 && PPU.BGMode != 6 && IPPU.DoubleWidthPixels)
    {
       /* Mixture of background modes used on screen - scale width
@@ -3150,5 +3204,6 @@ void S9xUpdateScreen(void)
    /* Double the height of the pixels just drawn */
    FIX_INTERLACE(GFX.Screen, false, GFX.ZBuffer);
 
+#endif
    IPPU.PreviousLine = IPPU.CurrentLine;
 }
-- 
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