valerybokov opened a new pull request, #535:
URL: https://github.com/apache/pdfbox/pull/535

   **Problem**
   
   Filled-in AcroForm field values (account numbers, amounts, names) rendered 
as garbled or blank CJK text in a real-world bank-receipt PDF where 
NeedAppearances is set and the AcroForm/DR font (SimSun) is:
   - not embedded (substituted from the OS), and
   - declared with a predefined, non-Identity encoding (UniGB-UTF16-H), instead 
of the usual Identity-H.
   
   **Root cause**
   
   PDCIDFontType2.encode()'s non-embedded branch always wrote the substituted 
font's own glyph index as the content-stream code, regardless of the font's 
declared /Encoding. That's only correct for Identity-H/V, where code == GID by 
convention.
   
   For a Uni...-UTF16-H/Uni...-UCS2-H encoding, the codespace is the raw 
UTF-16BE Unicode value (verified directly against the UniGB-UTF16-H CMap 
resource, e.g. <00a4> 167). Writing the substitute font's glyph index there 
instead produces a code that, once decoded again through the normal CID/Unicode 
round trip (PDCIDFontType2#codeToGID / PDType0Font#toUnicode), resolves to an 
unrelated, essentially arbitrary character — hence the garbled/blank text.
   
   **Fix**
   
   In the non-embedded branch of PDCIDFontType2.encode(), when the font's 
encoding is a predefined Uni... CMap (and not Identity-*), write the raw 
Unicode value as the code instead of the substitute font's glyph index, 
matching what that encoding's codespace actually expects.
   
   **Testing**
   
   - Reproduced with the two PDFs attached to the JIRA issue; before the fix, 
filled-in field values render as garbled/wrong CJK characters (or blank, 
matching the original report on an older PDFBox version). After the fix, both 
render correctly.
   - Added PDCIDFontType2SubstituteTest, which encodes a known GB1 character 
through the actual non-embedded SimSun font from the JIRA fixture and asserts 
the round trip resolves to the same glyph the substitute font's own Unicode 
cmap would give directly. Skips (via assumeTrue) if the environment has no 
suitable CJK substitute font installed.


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