Fix display of Unicode text.

Turns out that SWI-Prolog's wide string functions, which I started
using in 03fe361, do not convert between narrow Prolog atoms and wide
C strings, as I mistakenly thought. Instead, they work with wide
Prolog atoms. In hindsight, it is not surprising.

1 files changed, 18 insertions, 0 deletions

diff --git a/c/common.cpp b/c/common.cpp
index 4ce95a0..155c099 100644
--- a/c/common.cpp
+++ b/c/common.cpp
@@ -57,6 +57,24 @@ Library::~Library()
 	FreeLibrary(m_hModule);
 }
 
+/* Convert narrow unmanaged string to narrow/wide basic string. */
+template <>
+std::basic_string<char> BstrFromSz(const char* sz, int)
+{
+	return std::string(sz);
+}
+
+template <>
+std::basic_string<wchar_t> BstrFromSz(const char* sz, int iCp)
+{
+	int cbMultiByte = strlen(sz)+1;
+	int cchWideChar = MultiByteToWideChar(iCp, 0, sz, cbMultiByte, NULL, 0);
+	std::wstring wstr(cchWideChar, 0);
+	if (!MultiByteToWideChar(iCp, 0, sz, cbMultiByte, wstr.data(), cchWideChar))
+		throw Win32Error(GetLastError());
+	return wstr;
+}
+
 /* Move message box to center of main window. */
 static LRESULT CALLBACK CBTProc(const int nCode, const WPARAM wParam, const LPARAM lParam) noexcept
 {