TeX Code for making tooltips

tooltip.tex

%  Decoding the PDF primitives used by these functions is somewhat possible with
%  the help of the PDF spec:
%
%      http://www.adobe.com/devnet/pdf/pdf_reference.html
%

% Attempt #1
% Adapted from a post by Herbert Voss on comp.text.tex:
%
%    https://groups.google.com/d/msg/comp.text.tex/hjYT89EzN_E/MWXw1eksMhkJ
%
\newcounter{tooltip}
\def\tooltiptarget{\phantom{\rule{1mm}{1mm}}}  % Size of the mouse over area that will trigger the tooltip
\newcommand\tooltip[1]{%
  \leavevmode\pdfstartlink user{%
    /Subtype /Widget             % Defines the object as type 'Widget'
    /TU (#1)                     % Contents for the tooltip
    /T (tooltip \thetooltip)     % Tooltip number, required for Acrobat to display it
    /FT/Btn                      % Formtype of button, activates a change in the pointer and the tooltip
    /Ff 65536                    % Form flags, no idea what they mean exactly, but keeps the PDF viewer from asking "do you want to save?"
    /H/N                         % Highlighting mode: N for no highlighting when the user interacts with the button
  }%
  \tooltiptarget%
  \pdfendlink%
  \stepcounter{tooltip}%
}

% Pros: Works.  Is clean.
% Cons: Don't understand everything.  Longish delay between mouseover and tooltip display and no idea on how to change that.
% Relevant pages in the spec:
%   Section 12.5:       Annotations (page 389)
%   Section 12.5.6.19:  Widget Annotations (page 416)
%   Section 12.7:       Interactive Forms (page 439)


% Attempt #2
% Adapted from a post by Mycroft on comp.text.tex:
%
%     https://groups.google.com/d/msg/comp.text.tex/yTZx-SWGAhA/ywnM4_NgSeUJ
%
\def\tooltiptarget{\phantom{\rule{1mm}{1mm}}}
\newcommand\tooltip[1]{%
  \leavevmode\pdfstartlink user{%
    /Subtype /Text
    /CA  0                   % Icon opacity. Preview ignores this.
    /Name /Comment           % Sets the icon to be a comment balloon
    /Contents  (#1)
  }%
  \tooltiptarget%
  \pdfendlink%
}

% Pros: Works.  Concise.  Very snappy under Acrobat Reader.  Relevent sections of the spec are easier to understand.
% Cons: Preview completely ignores /CA 0 which means "set the ugly icon to be transparent plz!"
% Relevant pages in the spec:
%   Section 12.5:       Annotations (page 389)
%   Section 12.5.6.4:   Text Annotations (page 416)


% Attempt #3
% Obtained by blending attempt #2 with some code from the cooltips package:
%
%     http://tug.ctan.org/cgi-bin/ctanPackageInformation.py?id=cooltooltips
%
\def\tooltiptarget{\phantom{\rule{1mm}{1mm}}}

\newbox\tempboxa
\setbox\tempboxa=\hbox{} 
\immediate\pdfxform\tempboxa 
\edef\emptyicon{\the\pdflastxform}

\newcommand\tooltip[1]{%
  \leavevmode\pdfstartlink user{%
    /Subtype /Text
    /Contents  (#1)
    /AP <<
      /N \emptyicon\space 0 R   % Defines an empty icon for the tooltip
    >>
    /Open false
  }%
  \tooltiptarget%
  \pdfendlink%
}

% Pros: Gets rid of icons in preview.
% Cons: Preview still has a large target area to the lower left of the point that should not be there.
% Relevant pages in the spec:
%   Section 12.5:       Annotations (page 389)
%   Section 12.5.5:     Appearance Streams (page 396)
%   Section 12.5.6.4:   Text Annotations (page 416)