I am new to creating/editing fonts. I want to create a font with custom symbol for "glyph not found". I have downloaded FontForge as it seems to be a widespread free font editing program. I was hoping first U+0000 NUL, Default Character would be that, but it seems that I was wrong. I cannot find any info on how to make your own "glyph not found" symbol on google, maybe here somebody could help?
So far as I'm aware there is no “glyph not found” character. Different programs use different graphic presentations. An empty narrow rectangle is a common rendering, but not the only one. It could also be a rectangle with a question mark in it or with the code number of the character, in hexadecimal, in it.
From the Unicode Spec:
- may be used to represent a missing ideograph
- → U+20DE $⃞ combining enclosing square
The Unicode glossary entry says:
It often is shown as an open or black rectangle.