Symbian
Symbian OS Library

FAQ-1020 Why isn't the "undefined" glyph being displayed for unsupported characters

[Index][spacer] [Previous] [Next]



 

Classification: C++ Category: Fonts & Bitmaps
Created: 03/29/2004 Modified: 04/19/2004
Number: FAQ-1020
Platform: Symbian OS v6.1, Symbian OS v7.0, Symbian OS v7.0s, Symbian OS v8.0

Question:
If a character I select is not present in the current font then the editor should display an "undefined" glyph - but nothing seems to be displayed (and there is no warning)

Answer:
The font being used is a bitmap font, and/or the "replacement character" is not defined in the glyph index.

Bitmap fonts do not (by default) have the concept of a glyph to use for unsupported characters.
In Symbian OS v7.0s, Symbian added the concept of a "replacement character" to use in place of any undefined glyph's. This character is whatever character is at position F6DB in the bitmap font's glyph index.
In Symbian OS v6.1, if a bitmap font does not have a requested character, then nothing is displayed on the screen (note that the character is still written to the underlying document).

TrueType fonts do have the concept of an "undefined character" glyph which will be used (This is font specific, but it is usually an empty box). Therefore a glyph will be displayed for all versions of Symbian OS.