(latex2e.info)Lengths

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14 Lengths
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A "length" is a measure of distance.  Many LaTeX commands take a length
as an argument.

   Lengths come in two types.  A "rigid length" such as '10pt' does not
contain a 'plus' or 'minus' component.  (Plain TeX calls this a
"dimen".)  A "rubber length" (what Plain TeX calls a "skip") such as as
with '1cm plus0.05cm minus0.01cm' can contain either or both of those
components.  In that rubber length, the '1cm' is the "natural length"
while the other two, the 'plus' and 'minus' components, allow TeX to
stretch or shrink the length to optimize placement.

   The illustrations below use these two commands.

     % make a black bar 10pt tall and #1 wide
     \newcommand{\blackbar}[1]{\rule{#1}{10pt}}

     % Make a box around #2 that is #1 wide (excluding the border)
     \newcommand{\showhbox}[2]{%
       \fboxsep=0pt\fbox{\hbox to #1{#2}}}

This example uses those commands to show a black bar 100 points long
between 'XXX' and 'YYY'.  This length is rigid.

     XXX\showhbox{100pt}{\blackbar{100pt}}YYY

   As for rubber lengths, shrinking is simpler one: with '1cm minus
0.05cm', the natural length is 1cm but TeX can shrink it down as far as
0.95cm.  Beyond that, TeX refuses to shrink any more.  Thus, below the
first one works fine, producing a space of 98 points between the two
bars.

     XXX\showhbox{300pt}{%
       \blackbar{101pt}\hspace{100pt minus 2pt}\blackbar{101pt}}YYY

     XXX\showhbox{300pt}{%
       \blackbar{105pt}\hspace{100pt minus 1pt}\blackbar{105pt}}YYY

But the second one gets a warning like 'Overfull \hbox (1.0pt too wide)
detected at line 17'.  In the output the first 'Y' is overwritten by the
end of the black bar, because the box's material is wider than the 300pt
allocated, as TeX has refused to shrink the total to less than
309 points.

   Stretching is like shrinking except that if TeX is asked to stretch
beyond the given amount, it will do it.  Here the first line is fine,
producing a space of 110 points between the bars.

     XXX\showhbox{300pt}{%
       \blackbar{95pt}\hspace{100pt plus 10pt}\blackbar{95pt}}YYY

     XXX\showhbox{300pt}{%
       \blackbar{95pt}\hspace{100pt plus 1pt}\blackbar{95pt}}YYY

In the second line TeX needs a stretch of 10 points and only 1 point was
specified.  TeX stretches the space to the required length but it gives
you a warning like 'Underfull \hbox (badness 10000) detected at line
22'.  (We won't discuss badness.)

   You can put both stretch and shrink in the same length, as in '1ex
plus 0.05ex minus 0.02ex'.

   If TeX is setting two or more rubber lengths then it allocates the
stretch or shrink in proportion.

     XXX\showhbox{300pt}{%
       \blackbar{100pt}%  left
       \hspace{0pt plus 50pt}\blackbar{80pt}\hspace{0pt plus 10pt}%  middle
       \blackbar{100pt}}YYY  % right

The left and right bars take up 100 points, so the middle needs another
100.  The middle bar is 80 points so the two '\hspace''s must stretch
20 points.  Because the two are 'plus 50pt' and 'plus 10pt', TeX gets
5/6 of the stretch from the first space and 1/6 from the second.

   The 'plus' or 'minus' component of a rubber length can contain a
"fill" component, as in '1in plus2fill'.  This gives the length infinite
stretchability or shrinkability so that TeX could set it to any
distance.  Here the two figures will be equal-spaced across the page.

     \begin{minipage}{\linewidth}
       \hspace{0pt plus 1fill}\includegraphics{godel.png}%
       \hspace{0pt plus 1fill}\includegraphics{einstein.png}%
       \hspace{0pt plus 1fill}
     \end{minipage}

   TeX actually has three levels of infinity for glue components: 'fil',
'fill', and 'filll'.  The later ones are more infinite than the earlier
ones.  Ordinarily document authors only use the middle one (Note:
\hfill and Note: \vfill).

   Multiplying a rubber length by a number turns it into a rigid length,
so that after '\setlength{\ylength}{1in plus 0.2in}' and
'\setlength{\zlength}{3\ylength}' then the value of '\zlength' is '3in'.

Units of length

The units that LaTeX knows.

\setlength

Set the value of a length.

\addtolength

Add a quantity to a length.

\settodepth

Set a length to the depth of something.

\settoheight

Set a length to the height of something.

\settowidth

Set a length to the width of something.