xbanish
by joshua stein <jcs@jcs.org>
===============================================================================

xbanish hides the mouse cursor when you start typing, and shows it again when
the mouse cursor moves or a mouse button is pressed.  This is similar to
xterm's pointerMode setting, but xbanish works globally in the X11 session.

unclutter's -keystroke mode is supposed to do this, but it's broken[0].  I
looked into fixing it, but the unclutter source code is terrible, so I wrote
xbanish.

The name comes from ratpoison's "banish" command that sends the cursor to the
corner of the screen.


Implementation
===============================================================================

If the XInput extension is supported, xbanish uses it to request input from all
attached keyboards and mice.  If XInput 2.2 is supported, raw mouse movement
and button press inputs are requested which helps detect cursor movement while
in certain applications such as Chromium.

If Xinput is not available, xbanish recurses through the list of windows
starting at the root, and calls XSelectInput() on each window to receive
notification of mouse motion, button presses, and key presses.

In response to any available keyboard input events, the cursor is hidden.  On
mouse movement or button events, the cursor is shown.

xbanish initially hid the cursor by calling XGrabPointer() with a blank cursor
image, similar to unclutter's -grab mode, but this had problematic interactions
with certain X applications.  For example, xlock could not grab the pointer and
sometimes didn't lock, xwininfo wouldn't work at all, Firefox would quickly
hide the Awesome Bar dropdown as soon as a key was pressed, and xterm required
two middle-clicks to paste the clipboard contents.

To avoid these problems and simplify the implementation, xbanish now uses the
modern Xfixes extension[1] to easily hide and show the cursor with
XFixesHideCursor() and XFixesShowCursor().


0. https://bugs.launchpad.net/ubuntu/+source/unclutter/+bug/54148
1. http://cgit.freedesktop.org/xorg/proto/fixesproto/plain/fixesproto.txt