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tkerror.n
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1995-07-25
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67 lines
ttttkkkkeeeerrrrrrrroooorrrr((((nnnn)))) TTTTkkkk ((((7777....0000)))) ttttkkkkeeeerrrrrrrroooorrrr((((nnnn))))
_________________________________________________________________
NNNNAAAAMMMMEEEE
tkerror - Command invoked to process background errors
SSSSYYYYNNNNOOOOPPPPSSSSIIIISSSS
ttttkkkkeeeerrrrrrrroooorrrr _m_e_s_s_a_g_e
_________________________________________________________________
DDDDEEEESSSSCCCCRRRRIIIIPPPPTTTTIIIIOOOONNNN
The ttttkkkkeeeerrrrrrrroooorrrr command doesn't exist as built-in part of Tk.
Instead, individual applications or users can define a
ttttkkkkeeeerrrrrrrroooorrrr command (e.g. as a Tcl procedure) if they wish to
handle background errors.
A background error is one that occurs in a command that
didn't originate with the application. For example, if an
error occurs while executing a command specified with a bbbbiiiinnnndddd
of aaaafffftttteeeerrrr command, then it is a background error. For a
non-background error, the error can simply be returned up
through nested Tcl command evaluations until it reaches the
top-level code in the application; then the application can
report the error in whatever way it wishes. When a
background error occurs, the unwinding ends in the Tk
library and there is no obvious way for Tk to report the
error.
When Tk detects a background error, it invokes the ttttkkkkeeeerrrrrrrroooorrrr
command, passing it the error message as its only argument.
Tk assumes that the application has implemented the ttttkkkkeeeerrrrrrrroooorrrr
command, and that the command will report the error in a way
that makes sense for the application. Tk will ignore any
result returned by the ttttkkkkeeeerrrrrrrroooorrrr command.
If another Tcl error occurs within the ttttkkkkeeeerrrrrrrroooorrrr command then
Tk reports the error itself by writing a message to stderr.
The Tk script library includes a default ttttkkkkeeeerrrrrrrroooorrrr procedure |
that posts a dialog box containing the error message and |
offers the user a chance to see a stack trace that shows |
where the error occurred.
KKKKEEEEYYYYWWWWOOOORRRRDDDDSSSS
background error, reporting
Page 1 (printed 7/23/95)