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Paul Evans


Tickit::Debug - debug logging support for Tickit


This module implements the debug logging logic for Tickit. It is controlled by a number of environment variables. It exports a constant called DEBUG which will be true if the debug logging is enabled; allowing code to efficiently skip over it if it isn't.

Debug messages themselves each have a flag name, which is a short string identifying the Tickit subsystem or kind of event that caused it. A given subset of these flags can be enabled for printing. Flags not enabled will not be printed.


Each flag name starts with a upper-case letters indiciating the subsystem it relates to, then lower-case letters to indicate the particular kind of event or message.

I (Input)


Keyboard events


Mouse events


Resize events

W (Window)


Rectangles of damage queued on the root window for re-expose


Heirarchy changes on Windows (creates, deletes, re-orderings)


Calls to $win->scrollrect


Calls to $term->scrollrect on the root window as part of scrollrect


Expose events on Windows; which may result in calls to its on_expose handler. As this event is recursive, it prints an indent.



A comma-separated list of the flags or flag categories to enable for printing. Each potential flag exists in a category, given by the leading upper-case letters of its name. Entire categories can be enabled by name, as can individual flags.

See the "FLAGS" list above for the available flags.


If set, debug logging is sent directly to the opened filehandle given by this file descriptor number, rather than opening a log file.

Typically this is most useful to start a Tickit-based application in a new terminal but have its debug logging printed to STDERR of the original terminal the new one was launched from. For example

 $ TICKIT_DEBUG_FD=3 TICKIT_DEBUG_FLAGS=... $TERM perl my-tickit-app.pl 3>&2

This requests that Tickit::Debug log to file descriptor 3, which has been created by copying the original shell's standard error output, and so logging is printed to the shell this was run from.


Gives the name of a file to open and write logging to, if TICKIT_DEBUG_FD is not set. If this is not set either, a filename will be generated using the PID of the process, named as



Tickit::Debug->log( $flag => $format, @args )

Prints a line to the debug log if the specified $flag is present in the set of enabled flags.

Any arguments that are CODE references are called and replaced by the string value they return, then the line itself is generated by calling sprintf using the format string and the given arguments. It is then printed to the log, prefixed by the flag name and with a linefeed appended.

It is not necessary to include the \n linefeed in the $format itself.


Paul Evans <leonerd@leonerd.org.uk>