glenda.party
term% ls -F
term% pwd
$home/manuals/unix_v8/9/lens
term% cat index.txt
LENS(9.1)                                                            LENS(9.1)



NAME
       lens - bitmap magnifier

SYNOPSIS
       lens

DESCRIPTION
       Lens  is  an  interactive  screen bitmap magnifier.  When it starts, it
       displays an enlarged image of a magnifying glass in  its  layer,  which
       becomes a setting sun when lens wants to confirm a command to exit.

       The  first  item in the button 2 menu, which rotates among go, peek and
       stop, determines the activity of  the  magnifier.   Clicking  button  1
       serves as an abbreviation for selecting go or peek.  When the magnifier
       is going, a crawling-bordered rectangle is drawn around the source, and
       the  lens  window contains the magnified image.  The mouse controls the
       position of the source rectangle.

       During peeking, the rectangle last selected while going is  re-examined
       periodically,  and  the contents are magnified, whether or not the lens
       window is currently selected.

       When stopped, the lens window is inactive.

       The button 2 menu also allows changing the magnification  factor.   The
       magnification  factors  are chosen from the Fibonacci numbers, and menu
       items for the next size smaller and larger are presented as,  e.g.,  3x
       or  8x.  The current magnification factor is not displayed in the menu,
       only the next factors larger and smaller.   The  initial  magnification
       factor is two.

       Button  2 may also be used to select the intervals at which peeking up‐
       dates occur.  These intervals are selected, in ticks,  from  among  the
       powers of two, where a tick is one-sixtieth of a second.  These choices
       are presented as, e.g., 32 ticks or 128 ticks.   The  initial  interval
       between peeks is 64 ticks, approximately one second.

       The image window may be controlled by the button 2 menu item which tog‐
       gles between inset and full size.  In inset mode,  the  image  is  dis‐
       played  inside  the  image  window of the magnified lens icon.  In full
       size mode, the image is displayed in the entire lens window.

       The final buton 2 menu entry is exit.  A setting sun is displayed,  and
       button 3 must be clicked to confirm.

BUGS
       While  going,  the  display  is only refreshed when the mouse is moved.
       Inconsistent results may be obtained when lens is used to  examine  its
       own image window.

       While  peeking, it is assumed that the lens window contains an accurate
       magnification of what was on the screen at the time of the last  magni‐
       fication.  If lens is used to examine its own image, strange things may
       occur.

       Due to the bitmap reshaping techniques employed  by  the  magnification
       algorithms,  high  magnification factors will not work with large image
       windows.  Precisely, if the product of the vertical magnification  fac‐
       tor and the width of the destination rectangle overflows a signed short
       integer, predictable but undesirable results will occur.



                                                                     LENS(9.1)