Fix wstring conversion on Windows #1479
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On most Unices, wchar_t is 32 bits and typically holds UCS4 characters, which are big enough for any Unicode code point. On Windows, wchar_t is 16 bits and typically holds UTF-16 code units, which sometimes need to be used in pairs. This is because Windows introduced wchar_t before UCS4, UTF-8 and UTF-16 were invented, originally using them for UCS2 characters back when all of Unicode fit in sixteen bits. That meant that the existing string conversion code, which assumed std::wstring was a fixed-width encoding, would only work on Windows for the first 55295 code points (where UCS2 and UTF-16 were compatible), so anything outside the basic multilingual plane wouldn't work.
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I've also confirmed this works with MSYS2 as that's an edge case. |
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On most Unices, wchar_t is 32 bits and typically holds UCS4 characters, which are big enough for any Unicode code point.
On Windows, wchar_t is 16 bits and typically holds UTF-16 code units, which sometimes need to be used in pairs. This is because Windows introduced wchar_t before UCS4, UTF-8 and UTF-16 were invented, originally using them for UCS2 characters back when all of Unicode fit in sixteen bits.
That meant that the existing string conversion code, which assumed std::wstring was a fixed-width encoding, would only work on Windows for the first 55295 code points (where UCS2 and UTF-16 were compatible), so anything outside the basic multilingual plane wouldn't work.
I'll push a test app to vsgExamples in a minute or two. I've confirmed that this fixes everything on Windows and doesn't break anything on Ubuntu.