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<h1>Modifying <em>xv</em> Behavior</h1>
<p><i>xv</i> supports literally dozens of command line options
and X11 resources. Fortunately, it is doubtful that you'll ever
need to use more than a small few. The rest are provided mainly
for that 'one special case' application of <i>xv</i>... Note that
you do not have to specify the entire option name, only enough
characters to uniquely identify the option. Thus, '<tt>-geom</tt>'
is a fine abbreviation of '<tt>-geometry</tt>'.</p>
<h2><a name="command-line-options-overview">Command Line Options
Overview</a></h2>
<p>If you start <i>xv</i> with the command '<tt>xv -help</tt>',
the current (wildly out of control) list of options will be
displayed:</p>
<blockquote>
<p><font size="2"><tt>xv [-] [-/+24] [-/+2xlimit] [-/+4x3]
[-/+8] [-/+acrop] [-aspect w:h] [-best24] [-bg color] [-black
color] [-bw width] [-/+cecmap] [-cegeometry geom] [-/+cemap]
[-cgamma rval gval bval] [-cgeometry geom] [-/+clear]
[-/+close] [-/+cmap] [-cmtgeometry geom] [-/+cmtmap] [-crop x
y w h] [-cursor char#] [-DEBUG level] [-dir directory]
[-display disp] [-/+dither] [-drift dx dy] [-expand exp |
hexp:vexp] [-fg color] [-/+fixed] [-flist fname] [-gamma val]
[-geometry geom] [-grabdelay seconds] [-gsdev str] [-gsgeom
geom] [-gsres int] [-help] [-/+hflip] [-hi color] [-/+hist]
[-/+hsv] [-icgeometry geom] [-/+iconic] [-igeometry geom]
[-/+imap] [-/+lbrowse] [-lo color] [-/+loadclear] [-/+max]
[-/+maxpect] [-mfn font] [-/+mono] [-name str] [-ncols #]
[-/+ninstall] [-/+nodecor] [-/+nofreecols] [-/+nolimits]
[-/+nopos] [-/+noqcheck] [-/+noresetroot] [-/+norm]
[-/+nostat] [-/+owncmap] [-/+perfect] [-/+poll] [-preset #]
[-quick24] [-/+quit] [-/+random] [-/+raw] [-rbg color] [-rfg
color] [-/+rgb] [-RM] [-rmode #] [-/+root] [-rotate deg]
[-/+rv] [-/+rw] [-slow24] [-/+smooth] [-/+stdcmap]
[-tgeometry geom] [-/+vflip] [-/+viewonly] [-visual type]
[-/+vsdisable] [-vsgeometry geom] [-/+vsmap] [-/+vsperfect]
[-wait seconds] [-white color] [-/+wloop] [filename ...]</tt></font></p>
</blockquote>
<p>Yes, as a matter of fact, I <i>am</i> a little embarrassed
about it.</p>
<p>One big change starting in <i>xv </i>3.10: In the past, most
of the command-line options were <i>toggles</i>, in that they
would normally turn some feature on, but if you had an X resource
that also turned that feature on, then they would turn that
feature <i>off. </i>Now, they are absolute settings. For
instance, '<tt>-rv'</tt> turns on reverse video mode, regardless
of the setting of the '<tt>xv.reverse'</tt> resource, and '<tt>+rv'</tt>
turns <i>off</i> reverse video mode, regardless of the setting of
the '<tt>xv.reverse'</tt> resource. (Thanks Peder!)</p>
<h2><a name="general-options">General Options</a></h2>
<p>Note: In the following sections, the part of the option name
shown in <b>boldface</b> is the shortest allowable abbreviation
of the option in question.</p>
<dl>
<dt><a name="help"><b>-he</b><tt>lp</tt></a></dt>
<dd>Print usage instructions, listing the current available
command-line options. Any unrecognized option will do
this as well. </dd>
<dt> </dt>
<dt><a name="display"><b>-dis</b><tt>play</tt> <i>disp</i></a></dt>
<dd>Specifies the display that <i>xv</i> should attempt to
connect to. If you don't specify a display, <i>xv</i>
will use the environment variable <tt>$DISPLAY</tt> . </dd>
<dt> </dt>
<dt><a name="fg"><b>-fg</b> <i>color</i></a></dt>
<dd>Sets the foreground color used by the windows. </dd>
<dd>(Resource name: <tt>foreground</tt> . Type: string)</dd>
<dt> </dt>
<dt><a name="bg"><b>-bg</b> <i>color</i></a></dt>
<dd>Sets the background color used by the windows. </dd>
<dd>(Resource name: <tt>background</tt> . Type: string) </dd>
<dt> </dt>
<dt><a name="hi"><b>-hi</b> <i>color</i></a></dt>
<dd>Sets the highlight color used for the top-left edges of
the control buttons. </dd>
<dd>(Resource name: <tt>highlight</tt> . Type: string)</dd>
<dt> </dt>
<dt><a name="lo"><b>-lo</b> <i>color</i></a></dt>
<dd>Sets the lowlight color used for the bottom-right edges
of the control buttons, and also the background of some
windows. </dd>
<dd>(Resource name: <tt>lowlight</tt> . Type: string)</dd>
<dt> </dt>
<dt><a name="bw"><b>-bw</b> <i>bwidth</i></a></dt>
<dd>Sets the width of the border on the windows. Your window
manager may choose to ignore this, however. </dd>
<dd>(Resource name: <tt>borderWidth</tt> . Type: integer)</dd>
</dl>
<h2><a name="sizing-options">Image Sizing Options</a></h2>
<dl>
<dt><a name="geometry"><b>-ge</b><tt>ometry</tt> <i>geom</i></a></dt>
<dd>Lets you specify the size and placement of the 'image'
window. It's most useful when you only specify a
position, and let <i>xv</i> choose the size. If you
specify a size as well, <i>xv</i> will create a window of
that size, unless <tt>-fixed</tt> is specified. The geom
argument is in the form of a normal X geometry string
(e.g. "300x240" or "+10+10" or
"400x300+10+10") </dd>
<dd>(Resource name: <tt>geometry</tt> . Type: string)</dd>
<dt> </dt>
<dt><a name="fixed"><b>-</b>/<b>+fi</b><tt>xed</tt></a></dt>
<dd>Only used in conjunction with the <tt>-geometry</tt>
option. If you specify a window size with the <tt>-geometry</tt>
option, <i>xv</i> will normally stretch the picture to
exactly that size. This is not always desirable, as it
may seriously distort the aspect ratio of the picture.
Specifying the <tt>-fixed</tt> option corrects this
behavior by instructing <i>xv</i> to use the specified
geometry size as a maximum window size. It will preserve
the original aspect ratio of the picture. ( <tt>+fixed</tt>
turns off this feature, forcing the image to be exactly
the size specified by the <tt>-geometry</tt> option.) <p>For
example, if you give a rectangular geometry of '320x240',
and you try to display a square picture with a size of
'256x256', the window opened will actually be '240x240',
which is the largest square that still fits in the
'320x240' rectangle that was specified.</p>
<p>(Resource name: <tt>fixed</tt> . Type: boolean)</p>
</dd>
<dt><a name="expand"><b>-e</b><tt>xpand</tt> <i>exp</i></a></dt>
<dd>Lets you specify an initial expansion or compression
factor for the picture. You can specify floating-point
values. Values larger than zero multiply the picture's
dimensions by the given factor. (i.e., an expand factor
of '3' will make a 320x200 image display as 960x600). <p>Factors
less than zero are treated as reciprocals. (i.e., an
expand factor of '-4' makes the picture 1/4 th its normal
size.). '0' is not a valid expansion factor.</p>
<p>You can also specify a pair of expansion values,
separated by a colon, to set different horizontal and
vertical expansion ratios. For instance, '3:2' would
expand images 3x horizontally, and 2x vertically.</p>
<p>(Resource name: <tt>expand</tt> . Type: string) </p>
</dd>
<dt><a name="aspect"><b>-as</b><tt>pect</tt> <i>w:h</i></a></dt>
<dd>Lets you set an initial aspect ratio, and also sets the
value used by the <b>Aspect</b> command. The aspect ratio
of nearly every X display (and, in fact, <i>any</i>
civilized graphics display) is 1:1. What this means is
that pixels appear to be 'square'. A 100 pixel wide by
100 pixel high box will appear on the screen as a square.
Unfortunately, this is not the case with some screens and
digitizers. The <tt>-aspect</tt> option lets you stretch
the picture so that the picture appears correctly on your
display. Unlike the other size- related options, this one
doesn't care what the size of the overall picture is. It
operates on a pixel-by-pixel basis, stretching each image
pixel slightly, in either width or height, depending on
the ratio. <p>Aspect ratios greater than '1:1' (e.g.,
'4:3') make the picture wider than normal. Aspect ratios
less than '1:1' (e.g. '2:3') make the picture taller than
normal. (Useful aspect ratio: A 512x480 image that was
supposed to fill a standard 4x3 video screen (produced by
many video digitizers) should be displayed with an aspect
ratio of '5:4')</p>
<p>(Resource name: <tt>aspect</tt> . Type: string)</p>
</dd>
</dl>
<h2><a name="color-allocation-options">Color Allocation Options</a></h2>
<dl>
<dt><a name="ncols"><b>-nc</b><tt>ols</tt> <i>nc</i></a></dt>
<dd>Sets the maximum number of colors that <i>xv</i> will
use. By default, this is 'as many as it can get'.
However, you can set this to smaller values for
interesting effect. If you set it to '0', it will display
the picture by dithering with 'black' and 'white'. (The
actual colors used can be set by the <tt>- black</tt> and
<tt>-white</tt> options, below.) <p>The other major use
of this option is to limit the number of colors used when
putting up an image that's going to be hanging around for
a while. (i.e., an image in the root window) You may want
to limit the number of colors used for such images so
that other programs will still have some colorcells
available for their own use.</p>
<p>(Resource name: <tt>ncols</tt> . Type: integer)</p>
</dd>
<dt><a name="rw"><b>-</b>/<b>+rw</b></a></dt>
<dd>Tells <i>xv</i> to use read/write color cells. Normally, <i>xv</i>
allocates colors read- only, which allows it to share
colors with other programs. If you use read/write color
cells, no other program can use the colors that <i>xv</i>
is using, and vice-versa. The major reason to do such a
thing is that using read/write color cells allows the <b>Apply</b>
function in the <i>xv color editor</i> window to operate
much faster. ( <tt>+rw</tt> forces <i>xv</i> to use
read-only color, the default) <p>(Resource name: <tt>rwColor</tt>
. Type: boolean)</p>
</dd>
<dt><a name="perfect"><b>-</b>/<b>+pe</b><tt>rfect</tt></a></dt>
<dd>Makes <i>xv</i> try 'extra hard' to get all the colors it
wants. In particular, when <tt>-perfect</tt> is
specified, <i>xv</i> will allocate and install its own
colormap if (and only if) it was unable to allocate all
the desired colors. This option is not allowed in
conjunction with the <tt>-root</tt> option. <p>(Resource
name: <tt>perfect</tt> . Type: boolean)</p>
</dd>
<dt><a name="owncmap"><b>-</b>/<b>+o</b><tt>wncmap</tt></a></dt>
<dd>Like '<tt>-perfect'</tt>, only this option forces <i>xv</i>
to always allocate and install its own colormap, thereby
leaving the default colormap untouched. <p>(Resource
name: <tt>ownCmap</tt> . Type: boolean)</p>
</dd>
<dt><a name="stdcmap"><b>-</b>/<b>+st</b><tt>dcmap</tt></a></dt>
<dd>Puts <i>xv</i> into <b>Use Std. Colormap</b> mode. All
images will be shown dithered using the same set of
colors. This lets you run multiple copies of <i>xv</i> to
display multiple images simultaneously, and still have
enough colors to go around. <p>(Resource name: <tt>useStdCmap</tt>
. Type: boolean)</p>
</dd>
<dt><a name="cecmap"><b>-</b>/<b>+cec</b><tt>map</tt></a></dt>
<dd>Specifies whether <i>xv</i> installs the image's colormap
in the <i>xv color editor</i> window, as well as in the
image's window. By default, the program does not install
the colormap in the color editor window, as this often
makes the color editor window unreadable. Note, however
that the <i>Colormap Editor</i> tool will be appear
somewhat misleading. (This option only applies when the '<tt>-perfect'</tt>
or '<tt>-owncmap'</tt> options create their own
colormaps.) <p>(Resource name: <tt>ceditColorMap</tt> .
Type boolean)</p>
</dd>
<dt><a name="ninstall"><b>-</b>/<b>+ni</b><tt>nstall</tt></a></dt>
<dd>Prevents <i>xv</i> from 'installing' its own colormap,
when the <tt>-perfect</tt> or <tt>-owncmap</tt> options
are in effect. Instead of installing the colormap, it
will merely 'ask the window manager, nicely' to take care
of it. This is the correct way to install a colormap
(i.e., ask the WM to do it), unfortunately, it doesn't
actually seem to work in many window managers, so the
default behavior is for <i>xv</i> to handle installation
itself. However, this has been seen to annoy one window
manager (<i>dxwm</i>), so this option is provided if your
WM doesn't like programs installing their own colormaps. <p>(Resource
name: <tt>ninstall</tt> . Type: boolean)</p>
</dd>
</dl>
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