NAME

"Tickit::Debug" - debug logging support for "Tickit"

DESCRIPTION

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.

FLAGS

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

B (RenderBuffer)

Drawing operations

Flushing

State stack save/restore

Transformations (translate, clip, mask)

I (Input)

Keyboard events

Mouse events

Resize events

W (Window)

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

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

Calls to "$win->scrollrect"

Wsr

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.

ENVIRONMENT

TICKIT_DEBUG_FLAGS

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.

TICKIT_DEBUG_FD

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.

TICKIT_DEBUG_FILE

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-PID.log

METHODS

log

   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 list of values 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.

AUTHOR

Paul Evans <leonerd@leonerd.org.uk>