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 in a few hours.

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


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

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.  When a key press occurs, the cursor is hidden.  When
the mouse moves or a button is pressed, 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().  It also uses the Xinput extension
to receive global keystroke and mouse movement events, falling back on its old
behavior of calling XSelectInput() on every X11 window when the extension is
not available.  This works around issues receiving keystroke data in Firefox
and some other Gtk applications.


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