%%
%% This is file `novel-CalculateLayout.sty', part of `novel' document class.
%% Copyright 2017-2023 Robert Allgeyer.
%% 
%% It may be distributed and/or modified under the
%% conditions of the LaTeX Project Public License, either version 1.3c
%% of this license or (at your option) any later version.
%% The latest version of this license is in
%%    http://www.latex-project.org/lppl.txt
%% and version 1.3c or later is part of all distributions of LaTeX
%% version 2005/12/01 or later.
%% 
%%
\ProvidesFile{novel-CalculateLayout.sty}%
[2023/02/08 v1.80 LaTeX file (layout calculations)]
%%

%%
%% This file is loaded \AtEndPreamble, which precedes \AtBeginDocument.
%%



%% PROVIDE DEFAULT TRIM SIZE, MARGINS, AND NORMAL EM SIZE, IF NOT SET BY USER
%% ----------------------------------------------------------------------------
% Default Trim Size is 5.5in W x 8.5in H, unless \SetTrimSize used.
% This size is typical of American P.O.D. softcover fiction:
\if@SetTrimSize\else
  \gsetlength\@TrimWidth{5.5in}
  \gsetlength\@TrimHeight{8.5in}
\fi
% Default margins based on Trim Height, unless \SetMargins used:
\if@SetMargins\else
  \ifdimcomp{\@TrimHeight}{<}{8.99in}{ % small sizes:
    \gsetlength\@TopMargin{0.5in}
    \gsetlength\@OuterMargin{0.5in}
    \gsetlength\@BottomMargin{0.5in}
    \gsetlength\@InnerMargin{0.75in}
  }{ % medium sizes:
    \ifdimcomp{\@TrimHeight}{<}{9.99in}{ %
      \gsetlength\@TopMargin{0.75in}
      \gsetlength\@OuterMargin{0.75in}
      \gsetlength\@BottomMargin{0.75in}
      \gsetlength\@InnerMargin{1in}
    }{ % large sizes:
      \gsetlength\@TopMargin{1in}
      \gsetlength\@OuterMargin{1in}
      \gsetlength\@BottomMargin{1in}
      \gsetlength\@InnerMargin{1.25in}
    } %
  } %
\fi
% Default normal em size is based on Trim Width:
\if@FontSizeSet\else
  \ifdimcomp{\@TrimWidth}{<}{5.49in}{
    \gsetlength\@SetFontSize{11pt} % smaller books
  }{
    \ifdimcomp{\@TrimWidth}{<}{6.24in}{
      \gsetlength\@SetFontSize{11.4pt} % medium books
    }{
      \gsetlength\@SetFontSize{12pt} % larger books
    } %
  } %
\fi
%% end set default trim, margins, normal em size.


%% THEORY OF PAGE LAYOUT
%% ----------------------------------------------------------------------------
% The "available width" is the trim width minus the outer and inner margins:
\newlength\@AvailableWidth
\gsetlength\@AvailableWidth{\@TrimWidth-\@OuterMargin-\@InnerMargin}
% The "occupied width" of the text block is the TeX dimension \textwidth.
%   Your originally set layout can always fill the available width.
\gsetlength\textwidth{\@AvailableWidth}
% The "available height" is the trim height minus the top and bottom margins:
\newlength\@AvailableHeight
\gsetlength\@AvailableHeight{\@TrimHeight-\@TopMargin-\@BottomMargin}
% The "occupied height" includes header, textblock, footer, and allowances
%   for risers/diacriticals at top, descenders at bottom. It must fit within
%   the available height. This is the tricky part, so pay attention:
% In `novel' class, the topmost line of text (main block or header)
%   is positioned with its baseline at 1 normal em below available top.
%   That provides good clearance for uppercase letters with diacritical marks.
% The lowermost line of text (main block or footer) is positioned with its
%   baseline at 0.3 normal em above available bottom. This provides
%   good clearance for descenders.
% So, if your text does not have uppercase diacriticals, or if you use
%   a footer with lining numbers (no descenders), then the upper/lower margins
%   will appear to be a little larger than you set them.
% The headjump includes the line itself, plus any added gap to the main text.
%   An unused jump is re-set to 0:
\if@HasHeader\else\gdef\@HeadJump{0}\fi
%%
% TeX assumes that your layout has a footer, even if you do not want one.
%   Novel handles this by setting the baseline of the mandatory footer at
%   1 normal baselineskip below the last line of main text. Then, one line is
%   subtracted from the occupied line count. That places the empty, unused
%   virtual footer in the lower margin, where it does not matter. When you
%   do have a footer, the necessary line space is added, and the content
%   is positioned from the virtual footer using \smash and \raisebox.
%   Yes, it is complicated, but it handles more layout possibilities.
%   The \@FootJumpFix is one less than \@FootJump, or -1 when no footer:
\if@HasFooter
  \FPsub\@FootJumpFix{\@FootJump}{1}
\else
  \gdef\@FootJumpFix{-1}
\fi
% Putting it all together, the "occupied height" is:
%   1.3\@SetFontSize + (\@HeadJump+\@LinesPerPage+\@FootJumpFix)\baselineskip
%
%% end theory of page layout.


%% SET DEFAULT LINES PER PAGE, IF NOT SET BY USER
%% ----------------------------------------------------------------------------
% Lines per page refers only to the main text block, not header/footer:
\if@LinesPerPage\else
  % Estimate \baselineskip as 1.3\@SetFontSize, which is a comfortable value.
  % Calculate resulting \@LinesPerPage, then proceed as if set.
  % Actual \baselineskip will be re-calculated later.
  \edef\@tempLPP{%
    \fpeval{% package xfp
      (\@AvailableHeight - 0.3\@SetFontSize) % adjusts for final descenders
      / (1.3*\@SetFontSize) % denominator, with desired skip/em ratio
      -\@HeadJump -\@FootJumpFix % adjustments
    }%
  } %
  \FPtrunc{\@LinesPerPage}{\@tempLPP}{0} % final, integer floor
\fi
% Error if too few lines per page, whether set or default:
\FPiflt{\@LinesPerPage}{2}
  \ClassError{novel}{Calculated LinesPerPage less than 2}%
   {Too few lines. Either font size too big, or text height too small.}%
\fi
%% end set default lines per page.


%% CALCULATE BASELINESKIP
%% ----------------------------------------------------------------------------
% In `novel' class, the user does not directly set line-to-line spacing,
%   known as \baselineskip. Instead, \baselineskip is calculated from other
%   settings, so that "occupied height" fills "available height."
% See the above theory of layout, for the equations. Solve for \baselineskip =
%   (\@AvailableHeight-1.3\@SetFontSize)  divided by
%   (\@HeadJump+\@LinesPerPage+\@FootJumpFix)
%
\xdef\@AdjLPP{\fpeval{\@HeadJump+\@LinesPerPage+\@FootJumpFix}} % used often
\edef\@tempBLS{%
  \fpeval{(\@AvailableHeight-1.3\@SetFontSize) / \@AdjLPP}%
} %
\FPtrunc\@tempBLS{\@tempBLS}{2} % round down to 2 decimalplaces
\gsetlength\baselineskip{\@tempBLS pt}
%
% Error if \baselineSkip is too tight, in relation to normal em size:
\ifdimcomp{\baselineskip}{<}{1.2\@SetFontSize}{%
  \ClassError{novel}{Calculated baselineskip is too small}%
   {Default baselineskip is calculated from normal em size, ^^J%
     available text height, and lines per page. Result is too small. ^^J%
    Change something, then try again.}%
}{}%
%% end calculate baselineskip.


%% FINISH LAYOUT (but post-layout deals with special class options)
%% ----------------------------------------------------------------------------
% Caution if font size is small:
\ifdimcomp{\@SetFontSize}{<}{10pt}{ %
  \typeout{^^JClass `novel' Alert: Normal font at less than 10pt. ^^J%
    Whether or not this is too small, depends on circumstances. ^^J%
    Beware if you use footnotes, which are smaller. ^^J%
  }
}{} %
\ifdimcomp{\@SetFontSize}{<}{8.03pt}{ % 8 PostScript points (TeX bp)
  \ClassWarning{novel}{^^JNormal font at less than 8 points. ^^J%
    This is usually undesirable. May be rejected by some print services. ^^J%
  }
}{} %
% Default Media Size is same as Trim Size, unless \SetMediaSize used:
\if@MediaSize\else
    \gsetlength\paperwidth{\@TrimWidth}
    \gsetlength\paperheight{\@TrimHeight}
\fi
% Sanity check for cover art, which needs bleed:
\if@coverart
  \setlength\@tempLength{\paperwidth-\@TrimWidth}
  \ifthenelse{\dimtest{\@tempLength}{<}{6mm}}{%
    \ClassWarning{novel}{^^JBIG BAD WARNING! Insufficient bleed width ?^^J%
    Commercial printers generally require 0.125in (3mm) bleed,^^J%
    on all four sides of the Trim. But your dimensions do not provide this.^^J%
    Perhaps you need to increase the Media Width ?^^J}
  }{}
  \ifthenelse{\dimtest{\@tempLength}{>}{0.5in}}{%
    \ClassWarning{novel}{^^JBIG BAD WARNING! Too much bleed width ?^^J%
    Commercial printers generally require 0.125in (3mm) bleed,^^J%
    on all four sides of the Trim. Sometimes as much as 0.25in (6mm) each.^^J%
    But your dimensions provide more than this.
    Perhaps you need to decrease the Media Width ?^^J}
  }{}
  \setlength\@tempLength{\paperheight-\@TrimHeight}
  \ifthenelse{\dimtest{\@tempLength}{<}{5.83mm}}{% allows for pixel rounding
    \ClassWarning{novel}{^^JBIG BAD WARNING! Insufficient bleed height ?^^J%
    Commercial printers generally require 0.125in (3mm) bleed,^^J%
    on all four sides of the Trim. But your dimensions do not provide this.^^J%
    Perhaps you need to increase the MediaSize ?^^J}
  }{}
  \ifthenelse{\dimtest{\@tempLength}{>}{0.507in}}{% allows for pixel rounding
    \ClassWarning{novel}{^^JBIG BAD WARNING! Too much bleed height ?^^J%
    Commercial printers generally require 0.125in (3mm) bleed,^^J%
    on all four sides of the Trim. Sometimes as much as 0.25in (6mm) each.^^J%
    But your dimensions provide more than this.
    Perhaps you need to decrease the MediaSize ?^^J}
  }{}
\fi
% \textheight, normal font size, etc:
\gsetlength\textheight{\@LinesPerPage\baselineskip}
\renewcommand\normalsize{%
  \@setfontsize\normalsize{\strip@pt\@SetFontSize}{\strip@pt\baselineskip}%
}
\normalsize % from this point, the "real" normal font size is effective
%

%
\if@HasHeader
  % \headheight is mis-named. Text "height" is supposed to be measured upward
  %   from the baseline. But \headheight is measured from 0.3em below
  %   the baseline, to allow for descenders. Thus, to provide actual "height"
  %   of 1em, \headheight must be set to 1.3em:
  \gsetlength\headheight{1.3\@SetFontSize}
  % \headsep is a confusing term. It is the separation between the nominal
  %   0.3em descenders of header text, and one baseline above the baseline
  %   of the top line of main text. Got that? Let me do the thinking for you:
  \gsetlength\headsep{\@HeadJump\baselineskip-\baselineskip-0.3\@SetFontSize}
\else % no header, no problem:
  \gsetlength\headheight{0pt}
  \gsetlength\headsep{0pt}
\fi
% \oddsidemargin is at the left (inner, spine edge) of recto pages.
% Measured 1in (72.27pt) inside MediaBox, to the textblock. May be negative.

  \gsetlength\oddsidemargin{%
    \@InnerMargin+0.5\paperwidth-0.5\@TrimWidth-72.27pt%
  }

%
% \evensidemargin is at the left (outer edge) of verso pages.

  \gsetlength\evensidemargin{%
    \@OuterMargin+0.5\paperwidth-0.5\@TrimWidth-72.27pt%
  }

%
\if@closecrop
  \gsetlength\oddsidemargin{-0.9in}
  \gsetlength\evensidemargin{-0.9in}
\fi
%
% \topmargin is measured from 1in (72.27pt) below the top of the MediaBox,
%   to the top of whatever comes first (header or textblock). May be negative.
% For consistency, the topmost baseline (header or main text) will be
%   positioned at 1em below the margin.

  \gsetlength\topmargin{\@TopMargin+0.5\paperheight-0.5\@TrimHeight-72.27pt}
  \if@HasHeader\else
    \gsetlength\topmargin{\topmargin-\baselineskip+\@SetFontSize}
  \fi

% novel.cls sets a tentative em size (probably 10pt) so that packages requiring
%   an integer point size of 10, 11, or 12 will load without complaint.
% Then, the real point size is established here, when it is too late for
%   such packages to complain. Sneaky, eh?
% However, TeX places a strut in the header, rising 0.7x tentative size above
%   the header baseline. If the real size is too small, then the strut is
%   too large, which displaces the header text downward, simultaneously
%   shrinking the headsep and possibly affecting the textblock position.
% This unlikely problem cannot be fixed by adjusting the headheight, but it
%   can be fixed by adjusting the topmargin and headsep to compensate:
\ifdimcomp{\@SetFontSize}{<}{\@TentativeEmN pt}{ %
  \setlength\@tempLength{\@TentativeEmN pt}
  \gsetlength\topmargin{\topmargin-0.7\@tempLength+0.7\@SetFontSize}
  \gsetlength\headsep{\headsep+0.7\@tempLength-0.7\@SetFontSize}
}{} %
%%
% It seems that, unless specified by user, TeX may place the top text baseline
%   in a vertical position that depends on the height of text in that line.
% That height may vary, depending on ascenders or diacriticals there.
% In order to fix the position, \topskip gets a non-flexible setting.
% The best value is normal baselineskip, partly because it looks right,
%   and also to avoid underfull vboxes on nearly every page.
\gsetlength\topskip{\baselineskip} % absorber
% In `novel' class, footers are done in an unusual manner, as explained above.
% To fix the position of the virtual footer baseline:
\gsetlength\footskip{\baselineskip}
%% Sanity check: Trim Size must be contained within Media Size.
\ifthenelse{%
  \dimtest{\@TrimWidth}{>}{\paperwidth} %
  \OR \dimtest{\@TrimHeight}{>}{\paperheight}%
}{%
  \ClassError{novel}{Media Size too small for TrimSize}%
  {You wrote \string\SetMediaSize\space with length(s) too small ^^J%
   for the default Trim Size or your values in \string\SetTrimSize.}%
}{} %
% end sanity check
%% end finish layout.


%%
\endinput
%%
%% End of file `novel-CalculateLayout.sty'.


