flruler - a simple onscreen pixel measuring ruler for debugging GUIs


flruler [no options]


flruler displays a ruler on your desktop that you can drag around to measure elements in GUIs. Intended for GUI development/debugging to verify widget separations and sizes, though may also be used for general computer graphics, including measuring pixel distances of images, widgets in web applications, etc.

To move flruler, just click and drag it to where you want it. Press ESC to exit. You can make copies of the ruler by Middle-Clicking or hitting C. You can rotate the ruler(s) using the Up/Down/Left/Right arrow keys.


There are currently no command line options.


    'c'                   Make a copy of the current ruler (in focus)
    'esc'                 Closes current ruler (in focus)
    'q'                   Quit all rulers
    Up,Down,Left,Right    Re-orients ruler (arrow points to where zero will be)
    +                     Increase size of ruler by 10%
    -                     Decrease size of ruler by 10%


    Left-Drag             Drags current ruler around for positioning
    Left-Double-click     Reverses direction of current ruler's numbers
    Left-Triple-click     Rotates current ruler 90 degrees
    Middle-Click          Makes copy of current ruler


flruler Version 1.05 Written by Greg Ercolano.

The latest version of flruler can be downloaded from To build flruler from source, you need FLTK, the multi-platform GPL graphics toolkit (which supports Windows, Linux, OSX, IRIX..) from


To report bugs, send email to, and include "flruler bug report" in the Subject: of the message, or it will be ignored.


Copyright (C) 2012, 2006 Greg Ercolano.

This is free software; see the source for copying conditions. There is NO warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. For more information, see the LICENSE.txt file that came with the source.