.TH LENS 1
.SH NAME
lens \- interactive screen magnifier
.SH SYNOPSIS
.B lens
.SH DESCRIPTION
.I Lens
presents a magnified view in its window of an arbitrary area on the screen.
The default magnification is 4 (showing each pixel as a 4×4 pixel block in
.IR lens 's
window). This may be changed by typing a digit on the keyboard (with
.B 0
standing for 10), or by using the
.B +
and
.B -
keys to increase or decrease the magnification by one unit.
The lower limit is ×1; the upper ×16.
.PP
The interface to indicate what area to magnify is dictated by the mouse multiplexing rules of
.IR rio (1).
Start by pressing mouse button 1 in the
.I lens
window and dragging, with the button pressed, to the center of the area to magnify.
.I Lens
will update the display as the mouse moves.
Releasing the button freezes the
.I lens
display.
The magnified view is static\(ema snapshot, not a movie\(embut typing a space or
.B .
key  in the
.I lens
window will refresh the
display, as will changing the magnification.
.PP
To make counting pixels easier, typing a
.B g
toggles whether a checkerboard grid is imposed on the magnified area.
.SH SOURCE
.B /sys/src/cmd/lens.c
.SH BUGS
There should be an easier way to indicate what to magnify.