diff --git a/ddraw.rc b/ddraw.rc
index add2f79..8c28da4 100644
--- a/ddraw.rc
+++ b/ddraw.rc
@@ -1,6 +1,6 @@
 1 VERSIONINFO
-FILEVERSION 1,1,5,4
-PRODUCTVERSION 1,1,5,4
+FILEVERSION 1,1,5,5
+PRODUCTVERSION 1,1,5,5
 {
     BLOCK "StringFileInfo"
     {
@@ -8,13 +8,13 @@ PRODUCTVERSION 1,1,5,4
         {
             VALUE "CompanyName", "cncnet.org"
             VALUE "FileDescription", "DirectDraw replacement for C&C95 and Red Alert"
-            VALUE "FileVersion", "1.1.5.4"
+            VALUE "FileVersion", "1.1.5.5"
             VALUE "InternalName", "ddraw"
             VALUE "LegalCopyright", "Copyright (c) 2010-2018"
             VALUE "LegalTrademarks", ""
             VALUE "OriginalFileName", "ddraw.dll"
             VALUE "ProductName", "DirectDraw replacement for C&C95 and Red Alert"
-            VALUE "ProductVersion", "1.1.5.4"
+            VALUE "ProductVersion", "1.1.5.5"
             VALUE "Comments", "https://cncnet.org"
         }
     }
diff --git a/src/main.c b/src/main.c
index 8c75d50..9f7a403 100644
--- a/src/main.c
+++ b/src/main.c
@@ -895,9 +895,9 @@ HRESULT WINAPI DirectDrawCreate(GUID FAR* lpGUID, LPDIRECTDRAW FAR* lplpDD, IUnk
             "windowed=false\n"
             "; show window borders in windowed mode\n"
             "border=true\n"
-            "; maintain aspect ratio (GDI only!)\n"
+            "; maintain aspect ratio\n"
             "maintas=false\n"
-            "; use letter- or windowboxing to make a best fit (GDI only!)\n"
+            "; use letter- or windowboxing to make a best fit\n"
             "boxing=false\n"
             "; real rendering rate, -1 = screen rate, 0 = unlimited, n = cap\n"
             "maxfps=0\n"
diff --git a/src/render.c b/src/render.c
index d564413..ffa7244 100644
--- a/src/render.c
+++ b/src/render.c
@@ -117,8 +117,48 @@ DWORD WINAPI render_main(void)
     glGenTextures(1, &textureId);
     glBindTexture(GL_TEXTURE_2D, textureId);
     glTexImage2D(GL_TEXTURE_2D, 0, GL_RGB, tex_width, tex_height, 0, PIXEL_FORMAT, GL_UNSIGNED_BYTE, tex);
-    glViewport(0, 0, ddraw->render.width, ddraw->render.height);
 
+    DWORD dst_top = 0;
+    DWORD dst_left = 0;
+    DWORD dst_width = ddraw->render.width;
+    DWORD dst_height = ddraw->render.height;
+    
+    if (ddraw->maintas)
+    {
+        dst_width = ddraw->render.width;
+        dst_height = ((float)ddraw->height / ddraw->width) * dst_width;
+        
+        if (dst_height > ddraw->render.height)
+        {
+            dst_width = ((float)dst_width / dst_height) * ddraw->render.height;
+            dst_height = ddraw->render.height;
+        }
+         
+        dst_top = ddraw->render.height / 2 - dst_height / 2;
+        dst_left = ddraw->render.width / 2 - dst_width / 2;
+    }
+    else if (ddraw->boxing)
+    {
+        dst_width = ddraw->width;
+        dst_height = ddraw->height;
+
+        int i;
+        for (i = 20; i-- > 1;)
+        {
+            if (ddraw->width * i <= ddraw->render.width && ddraw->height * i <= ddraw->render.height)
+            {
+                dst_width *= i;
+                dst_height *= i;
+                break;
+            }
+        }
+
+        dst_top = ddraw->render.height / 2 - dst_height / 2;
+        dst_left = ddraw->render.width / 2 - dst_width / 2;
+    }
+
+    glViewport(dst_left, dst_top, dst_width, dst_height);
+    
     if(ddraw->render.filter)
     {
         glTexParameteri(GL_TEXTURE_2D,GL_TEXTURE_MIN_FILTER,GL_LINEAR);