Added a custom marshaler to decode screen texts received from Quake, which uses single-byte characters and a non-standard character set. Fixes string conversion errors and a fatal exception whenever the "ö" character is printed in the Zerstörer mod.

Assets/Scripts/Data/QExtensions.cs

@@ -15,7 +15,7 @@ public static class QExtensions
         for (int i = 0; i < count; ++i)
         {
             result[i] = Marshal.PtrToStructure<TStruct>(current);
-            current = new IntPtr(current.ToInt64() + size);
+            current = IntPtr.Add(current, size);
         }
         return result;
     }

Assets/Scripts/Modules/SystemModule.Interop.cs

@@ -50,18 +50,20 @@ public partial class SystemModule: CallbackHandler<SystemModule>
         public IntPtr SysFileTime;
         public IntPtr SysMkDir;
     }
-    
-    [UnmanagedFunctionPointer(CallingConvention.Cdecl)]
-    private delegate void SysPrintCallback(IntPtr target, [MarshalAs(UnmanagedType.LPStr)] string message);
+
+    [UnmanagedFunctionPointer(CallingConvention.Cdecl, CharSet = CharSet.Ansi)]
+    private delegate void SysPrintCallback(IntPtr target,
+        [MarshalAs(UnmanagedType.CustomMarshaler, MarshalTypeRef = typeof(QuakeTextMarshaler))] string message);
     
     [MonoPInvokeCallback(typeof(SysPrintCallback))]
     private static void Callback_SysPrint(IntPtr target, string message)
     {
         GetSelf(target).Print(message);
     }
-    
-    [UnmanagedFunctionPointer(CallingConvention.Cdecl)]
-    private delegate void SysErrorCallback(IntPtr target, [MarshalAs(UnmanagedType.LPStr)] string message);
+
+    [UnmanagedFunctionPointer(CallingConvention.Cdecl, CharSet = CharSet.Ansi)]
+    private delegate void SysErrorCallback(IntPtr target,
+        [MarshalAs(UnmanagedType.CustomMarshaler, MarshalTypeRef = typeof(QuakeTextMarshaler))] string message);
 
     [MonoPInvokeCallback(typeof(SysErrorCallback))]
     private static void Callback_SysError(IntPtr target, string message)
@@ -87,7 +89,7 @@ public partial class SystemModule: CallbackHandler<SystemModule>
         return GetSelf(target).DoubleTime();
     }
     
-    [UnmanagedFunctionPointer(CallingConvention.Cdecl)]
+    [UnmanagedFunctionPointer(CallingConvention.Cdecl, CharSet = CharSet.Ansi)]
     private delegate int SysFileOpenReadCallback(IntPtr target, [MarshalAs(UnmanagedType.LPStr)] string path, out int handle);
 
     [MonoPInvokeCallback(typeof(SysFileOpenReadCallback))]
@@ -96,7 +98,7 @@ public partial class SystemModule: CallbackHandler<SystemModule>
         return GetSelf(target).FileOpenRead(path, out handle);
     }
     
-    [UnmanagedFunctionPointer(CallingConvention.Cdecl)]
+    [UnmanagedFunctionPointer(CallingConvention.Cdecl, CharSet = CharSet.Ansi)]
     private delegate int SysFileOpenWriteCallback(IntPtr target, [MarshalAs(UnmanagedType.LPStr)] string path);
 
     [MonoPInvokeCallback(typeof(SysFileOpenWriteCallback))]
@@ -141,7 +143,7 @@ public partial class SystemModule: CallbackHandler<SystemModule>
         return GetSelf(target).FileWrite(handle, data, count);
     }
     
-    [UnmanagedFunctionPointer(CallingConvention.Cdecl)]
+    [UnmanagedFunctionPointer(CallingConvention.Cdecl, CharSet = CharSet.Ansi)]
     private delegate int SysFileTimeCallback(IntPtr target, [MarshalAs(UnmanagedType.LPStr)] string path);
 
     [MonoPInvokeCallback(typeof(SysFileTimeCallback))]
@@ -150,7 +152,7 @@ public partial class SystemModule: CallbackHandler<SystemModule>
         return GetSelf(target).FileTime(path);
     }
     
-    [UnmanagedFunctionPointer(CallingConvention.Cdecl)]
+    [UnmanagedFunctionPointer(CallingConvention.Cdecl, CharSet = CharSet.Ansi)]
     private delegate bool SysMkDirCallback(IntPtr target, [MarshalAs(UnmanagedType.LPStr)] string path);
 
     [MonoPInvokeCallback(typeof(SysMkDirCallback))]

Assets/Scripts/QuakeTextMarshaler.cs

@@ -0,0 +1,87 @@
+    using System;
+    using System.Runtime.InteropServices;
+    using System.Text;
+
+    /// <summary>
+    /// Quake uses a character set for its strings that is partially ASCII, but also partially nothing standard at all.
+    /// Inside the main PAK file is a character atlas texture and in order to print text, each char value inside of a
+    /// string is used to index a glyph in this atlas, which is then drawn to the screen.
+    ///  
+    /// Most strings received from Quake will work fine with the default ANSI charset marshaling, however some mods will
+    /// define their own character sets and use byte values >127 to print special characters. This is where the ANSI
+    /// marshaler breaks down, as these bytes are interpreted to signify multi-byte characters and result in a String
+    /// conversion error. To remedy this, we define our own single-byte character set that reflects the default one from
+    /// Quake and decode strings received from the engine by ourselves.
+    /// </summary>
+    public class QuakeTextMarshaler: ICustomMarshaler
+    {
+        private static QuakeTextMarshaler instance = null;
+
+        private static readonly char[] CharacterTable =
+        {
+            '·', ' ', ' ', ' ', ' ', '·', ' ', ' ', ' ', ' ', '\n', ' ', ' ', ' ', '·', '·',
+            '[', ']', '0', '1', '2', '3', '4', '5', '6', '7', '8', '9', '·', ' ', ' ', ' ',
+            ' ', '!', '"', '#', '$', '%', '&', '\'', '(', ')', '*', '+', ',', '-', '.', '/',
+            '0', '1', '2', '3', '4', '5', '6', '7', '8', '9', ':', ';', '<', '=', '>', '?',
+            '@', 'A', 'B', 'C', 'D', 'E', 'F', 'G', 'H', 'I', 'J', 'K', 'L', 'M', 'N', 'O',
+            'P', 'Q', 'R', 'S', 'T', 'U', 'V', 'W', 'X', 'Y', 'Z', '[', '\\', ']', '^', '_',
+            '`', 'a', 'b', 'c', 'd', 'e', 'f', 'g', 'h', 'i', 'j', 'k', 'l', 'm', 'n', 'o',
+            'p', 'q', 'r', 's', 't', 'u', 'v', 'w', 'x', 'y', 'z', '{', '|', '}', '~', '←',
+            '·', ' ', ' ', ' ', ' ', '·', ' ', ' ', ' ', ' ', '\n', ' ', ' ', ' ', '·', '·',
+            '[', ']', '0', '1', '2', '3', '4', '5', '6', '7', '8', '9', '·', ' ', ' ', ' ',
+            ' ', '!', '"', '#', '$', '%', '&', '\'', '(', ')', '*', '+', ',', '-', '.', '/',
+            '0', '1', '2', '3', '4', '5', '6', '7', '8', '9', ':', ';', '<', '=', '>', '?',
+            '@', 'A', 'B', 'C', 'D', 'E', 'F', 'G', 'H', 'I', 'J', 'K', 'L', 'M', 'N', 'O',
+            'P', 'Q', 'R', 'S', 'T', 'U', 'V', 'W', 'X', 'Y', 'Z', '[', '\\', ']', '^', '_',
+            '`', 'a', 'b', 'c', 'd', 'e', 'f', 'g', 'h', 'i', 'j', 'k', 'l', 'm', 'n', 'o',
+            'p', 'q', 'r', 's', 't', 'u', 'v', 'w', 'x', 'y', 'z', '{', '|', '}', '~', '←',
+        };
+        
+        public IntPtr MarshalManagedToNative(object managedObj)
+        {
+            if (managedObj == null)
+                return IntPtr.Zero;
+
+            if (!(managedObj is string str))
+                throw new MarshalDirectiveException("QuakeTextMarshaler must be used on a string.");
+
+            throw new NotImplementedException("QuakeTextMarshaler can only be used to decode text from Quake.");
+        }
+
+        public object MarshalNativeToManaged(IntPtr pNativeData)
+        {
+            byte b;
+            
+            var sb = new StringBuilder();
+            while ((b = Marshal.ReadByte(pNativeData)) != 0)
+            {
+                sb.Append(CharacterTable[b]);
+                pNativeData = IntPtr.Add(pNativeData, 1);
+            }
+
+            return sb.ToString();
+        }
+        
+        public void CleanUpManagedData(object managedObj)
+        {
+        }
+
+        public void CleanUpNativeData(IntPtr pNativeData)
+        {
+            // Free HGlobal memory if we decide to implement MarshalManagedToNative
+        }
+
+        public int GetNativeDataSize()
+        {
+            return -1;
+        }
+
+        public static ICustomMarshaler GetInstance(string cookie)
+        {
+            if (instance == null)
+                return instance = new QuakeTextMarshaler();
+
+            return instance;
+        }
+    }
+    

Assets/Scripts/QuakeTextMarshaler.cs.meta

@@ -0,0 +1,3 @@
+fileFormatVersion: 2
+guid: 23e2ec4793084710924ba442860bf2d6
+timeCreated: 1618677615