\tooltip[black]{foo}[blue!50]{Hint: What is the definition of foo?}
If the mouse is moved over 'foo' the tip is shown and it disappears immediately when the mouse is moved out.
In order to drag the tip around, 'foo' must be clicked. The tip remains visible. Move the mouse over the tip, click it and move it around. Click the tip once more to pin it down at the current position.
To hide the tip, wipe over 'foo' with the mouse.
Link text and tip text colours are optional. Besides pdftex
, all common drivers (xetex
, dvips
, ...) are supported.
It is recommended that <tip text>
is not wider than \linewidth
, <tiptext>
should be put into a \parbox
if necessary.
(Code by M. Scharrer from https://tex.stackexchange.com/a/17808 is used to compute initial left-shift for wider tip text boxes.)

%\documentclass[a6paper,12pt]{scrbook}
\documentclass[12pt]{scrbook}
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
%
% tooltips with LaTeX v. 2017/11/28
%
% \tooltip[*[*[*[*]]]][<link colour>]{<link text>}[<tip box colour>]{<tip text>}
%
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
%
% \tooltip --> draggable tip, visible on mouse-over, hidden on mouse-out
%
% \tooltip* --> draggable tip, toggle visiblity on mouse-over
%
% \tooltip** --> NON-draggable tip, visible on mouse-over, hidden on mouse-out
%
% \tooltip*** --> NON-draggable tip, toggle visiblity on mouse-over
%
% \tooltip**** --> NON-draggable tip, toggle visiblity on mouse-click (Evince!)
%
% Default link colour can be set with
%
% \usepackage[linkcolor=<colour>]{hyperref}
%
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
\usepackage{pdfbase}[2017/03/16]
\usepackage{xparse,ocgbase}
\usepackage{xcolor,calc}
\usepackage{tikzpagenodes}
\usetikzlibrary{calc}
\ExplSyntaxOn
\let\tpPdfLink\pbs_pdflink:nn
\let\tpPdfAnnot\pbs_pdfannot:nnnn\let\tpPdfLastAnn\pbs_pdflastann:
\let\tpAppendToFields\pbs_appendtofields:n
\def\tpPdfXform{\pbs_pdfxform:nnnnn{1}{1}{}{}}
\let\tpPdfLastXform\pbs_pdflastxform:
\ExplSyntaxOff
\makeatletter
\NewDocumentCommand{\tooltip}{%
ssssO{\ifdefined\@linkcolor\@linkcolor\else blue\fi}mO{yellow!20}m%
}{{%
\leavevmode%
\IfBooleanT{#2}{%
%for variants with two and more stars, put tip box on a PDF Layer (OCG)
\ocgbase@new@ocg{tipOCG.\thetcnt}{%
/Print<</PrintState/OFF>>/Export<</ExportState/OFF>>%
}{false}%
\xdef\tpTipOcg{\ocgbase@last@ocg}%
%prevent simultaneous visibility of multiple non-draggable tooltips
\ocgbase@add@ocg@to@radiobtn@grp{tool@tips}{\ocgbase@last@ocg}%
}%
\tpPdfLink{%
\IfBooleanTF{#4}{%
/Subtype/Link/Border[0 0 0]/A <</S/SetOCGState/State [/Toggle \tpTipOcg]>>
}{%
/Subtype/Screen%
/AA<<%
\IfBooleanTF{#3}{%
/E<</S/SetOCGState/State [/Toggle \tpTipOcg]>>%
}{%
\IfBooleanTF{#2}{%
/E<</S/SetOCGState/State [/ON \tpTipOcg]>>%
/X<</S/SetOCGState/State [/OFF \tpTipOcg]>>%
}{
\IfBooleanTF{#1}{%
/E<</S/JavaScript/JS(%
var fd=this.getField('tip.\thetcnt');%
if(typeof(click\thetcnt)=='undefined'){%
var click\thetcnt=false;%
var fdor\thetcnt=fd.rect;var dragging\thetcnt=false;%
}%
if(fd.display==display.hidden){%
fd.delay=true;fd.display=display.visible;fd.delay=false;%
}else{%
if(!click\thetcnt&&!dragging\thetcnt){fd.display=display.hidden;}%
if(!dragging\thetcnt){click\thetcnt=false;}%
}%
this.dirty=false;%
)>>%
}{%
/E<</S/JavaScript/JS(%
var fd=this.getField('tip.\thetcnt');%
if(typeof(click\thetcnt)=='undefined'){%
var click\thetcnt=false;%
var fdor\thetcnt=fd.rect;var dragging\thetcnt=false;%
}%
if(fd.display==display.hidden){%
fd.delay=true;fd.display=display.visible;fd.delay=false;%
}%
this.dirty=false;%
)>>%
/X<</S/JavaScript/JS(%
if(!click\thetcnt&&!dragging\thetcnt){fd.display=display.hidden;}%
if(!dragging\thetcnt){click\thetcnt=false;}%
this.dirty=false;%
)>>%
}%
/U<</S/JavaScript/JS(click\thetcnt=true;this.dirty=false;)>>%
/PC<</S/JavaScript/JS (%
var fd=this.getField('tip.\thetcnt');%
try{fd.rect=fdor\thetcnt;}catch(e){}%
fd.display=display.hidden;this.dirty=false;%
)>>%
/PO<</S/JavaScript/JS(this.dirty=false;)>>%
}%
}%
>>%
}%
}{{\color{#5}#6}}%
\sbox\tiptext{%
\IfBooleanT{#2}{%
\ocgbase@oc@bdc{\tpTipOcg}\ocgbase@open@stack@push{\tpTipOcg}}%
\fcolorbox{black}{#7}{#8}%
\IfBooleanT{#2}{\ocgbase@oc@emc\ocgbase@open@stack@pop\tpNull}%
}%
\edef\twd{\the\wd\tiptext}%
\edef\tht{\the\ht\tiptext}%
\edef\tdp{\the\dp\tiptext}%
\measureremainder{\whatsleft}\tipshift=0pt%
\ifdim\whatsleft<\twd\setlength\tipshift{\whatsleft-\twd}\fi%
\IfBooleanF{#2}{\tpPdfXform{\tiptext}}%
\raisebox{\heightof{#6}+\tdp}[0pt][0pt]{\makebox[0pt][l]{\hspace{\tipshift}%
\IfBooleanTF{#2}{\usebox{\tiptext}}{%
\tpPdfAnnot{\twd}{\tht}{\tdp}{%
/Subtype/Widget/FT/Btn/T (tip.\thetcnt)%
/AP<</N \tpPdfLastXform>>%
/MK<</TP 1/I \tpPdfLastXform/IF<</S/A/FB true/A [0.0 0.0]>>>>%
/Ff 65536/F 3%
/AA <<%
/U <<%
/S/JavaScript/JS(%
var fd=event.target;%
var mX=this.mouseX;var mY=this.mouseY;%
var drag=function(){%
var nX=this.mouseX;var nY=this.mouseY;%
var dX=nX-mX;var dY=nY-mY;%
var fdr=fd.rect;%
fdr[0]+=dX;fdr[1]+=dY;fdr[2]+=dX;fdr[3]+=dY;%
fd.rect=fdr;mX=nX;mY=nY;%
};%
if(!dragging\thetcnt){%
dragging\thetcnt=true;Int=app.setInterval("drag()",1);%
}%
else{app.clearInterval(Int);dragging\thetcnt=false;}%
this.dirty=false;%
)%
>>%
>>%
}%
\tpAppendToFields{\tpPdfLastAnn}%
}%
}}%
\stepcounter{tcnt}%
}}
\makeatother
\newsavebox\tiptext\newcounter{tcnt}
\newlength{\whatsleft}\newlength{\tipshift}
\newcommand{\measureremainder}[1]{%
\begin{tikzpicture}[overlay,remember picture]
\path let \p0 = (0,0), \p1 = (current page.east) in
[/utils/exec={\pgfmathsetlength#1{\x1-\x0}\global#1=#1}];
\end{tikzpicture}%
}
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
\begin{document}
\tooltip[black]{foo}[blue!50]{Hint: What is the definition of foo?}
with non-draggable tooltip: \tooltip**[black]{bar}[blue!50]{Hint: What is the definition of bar?}
\end{document}
fancytooltips
. The tooltip is inserted inline, no external file as requested. Moving the tooltip around is just a bonus feature (The tip text could be wider than the page).