From a52881eb724ee7c53d77ebb05b0c019bc64a6950 Mon Sep 17 00:00:00 2001
From: FunkyFr3sh <cc.red.alert.1@googlemail.com>
Date: Sun, 2 May 2021 16:21:06 +0200
Subject: [PATCH] #89 fixes blt/blitfast where source and dest sourface are the
 same

---
 src/config.c    |  5 ++++
 src/ddsurface.c | 75 +++++++++++++++++++++++++++++++++++++++++++------
 2 files changed, 71 insertions(+), 9 deletions(-)

diff --git a/src/config.c b/src/config.c
index 806798b..a6939f5 100644
--- a/src/config.c
+++ b/src/config.c
@@ -547,6 +547,11 @@ static void cfg_create_ini()
             "[Cultures2MP]\n"
             "handlemouse=false\n"
             "\n"
+            "; Blade & Sword\n"
+            "[comeon]\n"
+            "renderer=opengl\n"
+            "nonexclusive=true\n"
+            "\n"
 
             , fh);
         fclose(fh);
diff --git a/src/ddsurface.c b/src/ddsurface.c
index 17aa4a4..04095ee 100644
--- a/src/ddsurface.c
+++ b/src/ddsurface.c
@@ -200,13 +200,41 @@ HRESULT dds_Blt(IDirectDrawSurfaceImpl *This, LPRECT lpDestRect, LPDIRECTDRAWSUR
 
                 unsigned int dst_pitch = width * This->lx_pitch;
 
-                int i;
-                for (i = 0; i < height; i++)
+                if (This == src_surface)
                 {
-                    memcpy(dst, src, dst_pitch);
+                    if (dst_y > src_y)
+                    {
+                        src += src_surface->l_pitch * height;
+                        dst += This->l_pitch * height;
 
-                    src += src_surface->l_pitch;
-                    dst += This->l_pitch;
+                        for (int i = height; i-- > 0;)
+                        {
+                            src -= src_surface->l_pitch;
+                            dst -= This->l_pitch;
+
+                            memmove(dst, src, dst_pitch);
+                        }
+                    }
+                    else
+                    {
+                        for (int i = 0; i < height; i++)
+                        {
+                            memmove(dst, src, dst_pitch);
+
+                            src += src_surface->l_pitch;
+                            dst += This->l_pitch;
+                        }
+                    }
+                }
+                else
+                {
+                    for (int i = 0; i < height; i++)
+                    {
+                        memcpy(dst, src, dst_pitch);
+
+                        src += src_surface->l_pitch;
+                        dst += This->l_pitch;
+                    }
                 }
             }
             else
@@ -491,12 +519,41 @@ HRESULT dds_BltFast(IDirectDrawSurfaceImpl *This, DWORD dst_x, DWORD dst_y, LPDI
 
             unsigned int dst_pitch = dst_w * This->lx_pitch;
 
-            for (int i = 0; i < dst_h; i++)
+            if (This == src_surface)
             {
-                memcpy(dst, src, dst_pitch);
+                if (dst_y > src_y)
+                {
+                    src += src_surface->l_pitch * dst_h;
+                    dst += This->l_pitch * dst_h;
 
-                src += src_surface->l_pitch;
-                dst += This->l_pitch;
+                    for (int i = dst_h; i-- > 0;)
+                    {
+                        src -= src_surface->l_pitch;
+                        dst -= This->l_pitch;
+
+                        memmove(dst, src, dst_pitch);
+                    }
+                }
+                else
+                {
+                    for (int i = 0; i < dst_h; i++)
+                    {
+                        memmove(dst, src, dst_pitch);
+
+                        src += src_surface->l_pitch;
+                        dst += This->l_pitch;
+                    }
+                }
+            }
+            else
+            {
+                for (int i = 0; i < dst_h; i++)
+                {
+                    memcpy(dst, src, dst_pitch);
+
+                    src += src_surface->l_pitch;
+                    dst += This->l_pitch;
+                }
             }
         }
     }