Fix UTF-16 encoding of supplementary plane characters#171
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write_string() used a 0x100000 threshold instead of 0x10000 when deciding between a single UTF-16 code unit and a surrogate pair, and the surrogate path did not subtract the 0x10000 bias. Characters at U+10000 and above (emoji, CJK extensions) were emitted as raw 5-digit code points or with the wrong high surrogate, producing malformed UTF-16 in content strings drawn with unicode=true.
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I will be incorporating a subset of your fix but ATM it is a somewhat academic exercise since the current Unicode font support only maps plane 0... |
michaelrsweet
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write_string()mis-encodes any character at U+10000 or above when drawing text withunicode=true. Two bugs in the same branch: the threshold that picks a surrogate pair is0x100000instead of0x10000, so supplementary plane characters take the single-code-unit branch and print as a raw 5-hex-digit value (U+1F600 becomes1F600); and the surrogate formula never subtracts the0x10000bias, so even a character that reached the pair branch got the wrong high surrogate (D87Drather thanD83D). Both produce malformed UTF-16 in the content stream for emoji, CJK extension blocks, and other non-BMP text.The fix corrects the threshold and subtracts the bias before splitting into surrogates. BMP characters are unchanged.
Added a unit test in
do_unicode_tests(): it writesA, U+00E9, U+20AC, and U+1F600 withunicode=true, reads the content stream back, and checks for<004100E920ACD83DDE00>.