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Error Handling
Although every function usually returns meaningful values, there are
situations where indicating an error via the return value is not possible. For
example, requesting a charspace bounding box from a char of a font which is not
loaded will return a bounding box containing all zeroes. This cannot be
considered an error-condition since for characters like ``space'' it is
correct to return a bounding box containing all zeroes. Furthermore, there's no
consistent scheme which value should indicate what type of error. In order to
allow a unified error handling in applications, the global variable
T1_errno
has been introduced.
The functionality of T1_errno
is analogous to that of the global
errno
in C programs. T1_errno
is once set to 0 when the library
is initialized and never reset by any t1lib-function. It is set to specific
values when specific types of errors appear. An application may then act
appropriately and reset T1_errno
.
The errors that might appear can be roughly split into three categories as
described below.
Subsections
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2005-01-12