unicode - What does it mean when my text is displayed as Question Marks?

Question

I'm attempting to display some text in my program using (say) Windows GDI and some of the unicode characters are displayed as question marks? What is up?

See also: What does it mean when my text is displayed as boxes?

Answer 1

In Windows there are 2 common display problems that occur when trying to display Unicode characters:

1. text sometimes appears as question marks

   • This occurs when Unicode data is converted to an 8-bit character set encoding (or technically multi-byte characters) usually via the system codepage (but other code pages can be specified in the conversion calls). If the target 8-bit character set doesn't include the characters needed, any characters not representable in the target character set get converted to question marks.

2. text sometimes appears as boxes

   • This is a problem with the font not having the glpyh for a particular character. Boxes show up when there is a mismatch between Unicode characters in the document and those supported by the font. Specifically, the boxes represent characters not supported by the selected font.