LaTeX writer: new method for ensuring images don't overflow.

Previously we relied on graphicx internals and made global
changes to Gin to force images to be resized if they exceed
textwidth.  This approach is brittle and caused problems
with `\includesvg` (see #9660).

The new approach uses a new macro `\pandocbounded` that is
now defined in the LaTeX template. (Thanks here to Falk Hanisch in
mrpiggi/svg#60.)

The LaTeX writer has been changed to enclose `\includegraphics`
and `\includesvg` commands in this macro when they don't explicitly
specify a width or height.

Compatibility issues:  if custom templates are used with the
new LaTeX writer, they will have to be updated to include the
new `\pandocbounded` macro, or an error will be raised because
of the undefined macro.

Closes #9660.

data/templates/default.latex

@@ -299,15 +299,17 @@ $endif$
 $if(graphics)$
 \usepackage{graphicx}
 \makeatletter
-\def\maxwidth{\ifdim\Gin@nat@width>\linewidth\linewidth\else\Gin@nat@width\fi}
-\def\maxheight{\ifdim\Gin@nat@height>\textheight\textheight\else\Gin@nat@height\fi}
-\makeatother
-% Scale images if necessary, so that they will not overflow the page
-% margins by default, and it is still possible to overwrite the defaults
-% using explicit options in \includegraphics[width, height, ...]{}
-\setkeys{Gin}{width=\maxwidth,height=\maxheight,keepaspectratio}
+\newsavebox\pandoc@box
+\newcommand*\pandocbounded[1]{% scales image to fit in text height/width
+ \sbox\pandoc@box{#1}%
+ \Gscale@div\@tempa{\textheight}{\dimexpr\ht\pandoc@box+\dp\pandoc@box\relax}%
+ \Gscale@div\@tempb{\linewidth}{\wd\pandoc@box}%
+ \ifdim\@tempb\p@<\@tempa\p@\let\@tempa\@tempb\fi% select the smaller of both
+ \ifdim\@tempa\p@<\p@\scalebox{\@tempa}{\usebox\pandoc@box}%
+ \else\usebox{\pandoc@box}%
+ \fi%
+}
 % Set default figure placement to htbp
-\makeatletter
 \def\fps@figure{htbp}
 \makeatother
 $endif$

src/Text/Pandoc/Writers/LaTeX.hs

@@ -1094,8 +1094,11 @@ inlineToLaTeX (Image attr@(_,_,kvs) _ (source, _)) = do
  inHeading <- gets stInHeading
  return $
  (if inHeading then "\\protect" else "") <>
- (if isSVG then "\\includesvg" else "\\includegraphics") <>
- options <> braces (literal source'')
+ (case dimension Width attr `mplus` dimension Height attr of
+ Just _ -> id
+ Nothing -> ("\\pandocbounded" <>) . braces)
+ ((if isSVG then "\\includesvg" else "\\includegraphics") <>
+ options <> braces (literal source''))
 inlineToLaTeX (Note contents) = do
  setEmptyLine False
  externalNotes <- gets stExternalNotes

test/Tests/Writers/LaTeX.hs

@@ -70,7 +70,7 @@ tests = [ testGroup "code blocks"
  "\\begin{description}\n\\item[foo] ~ \n\\subsection{bar}\n\nbaz\n\\end{description}"
  , "containing image" =:
  header 1 (image "imgs/foo.jpg" "" (text "Alt text")) =?>
- "\\section{\\texorpdfstring{\\protect\\includegraphics{imgs/foo.jpg}}{Alt text}}"
+ "\\section{\\texorpdfstring{\\protect\\pandocbounded{\\includegraphics{imgs/foo.jpg}}}{Alt text}}"
  ]
  , testGroup "inline code"
  [ "struck out and highlighted" =:

test/command/5476.md

@@ -4,7 +4,7 @@
 ^D
 \begin{figure}
 \centering
-\includegraphics{test/lalune.jpg}
+\pandocbounded{\includegraphics{test/lalune.jpg}}
 \caption[moon]{moon\footnotemark{}}
 \end{figure}
 \footnotetext{the moon}

test/command/7181.md

@@ -4,7 +4,7 @@
 ^D
 \begin{figure}
 \centering
-\includegraphics[page=13,trim=1cm,clip,width=4cm]{slides.pdf}
+\pandocbounded{\includegraphics[page=13,trim=1cm,clip,width=4cm]{slides.pdf}}
 \caption{Global frog population.}
 \end{figure}
 

test/command/9045.md

@@ -4,7 +4,7 @@
 ^D
 \begin{figure}
 \centering
-\includegraphics{there.jpg}
+\pandocbounded{\includegraphics{there.jpg}}
 \caption{hi}\label{foo}
 \end{figure}
 ```

test/writer.latex

@@ -39,15 +39,17 @@
 \usepackage{xcolor}
 \usepackage{graphicx}
 \makeatletter
-\def\maxwidth{\ifdim\Gin@nat@width>\linewidth\linewidth\else\Gin@nat@width\fi}
-\def\maxheight{\ifdim\Gin@nat@height>\textheight\textheight\else\Gin@nat@height\fi}
-\makeatother
-% Scale images if necessary, so that they will not overflow the page
-% margins by default, and it is still possible to overwrite the defaults
-% using explicit options in \includegraphics[width, height, ...]{}
-\setkeys{Gin}{width=\maxwidth,height=\maxheight,keepaspectratio}
+\newsavebox\pandoc@box
+\newcommand*\pandocbounded[1]{% scales image to fit in text height/width
+ \sbox\pandoc@box{#1}%
+ \Gscale@div\@tempa{\textheight}{\dimexpr\ht\pandoc@box+\dp\pandoc@box\relax}%
+ \Gscale@div\@tempb{\linewidth}{\wd\pandoc@box}%
+ \ifdim\@tempb\p@<\@tempa\p@\let\@tempa\@tempb\fi% select the smaller of both
+ \ifdim\@tempa\p@<\p@\scalebox{\@tempa}{\usebox\pandoc@box}%
+ \else\usebox{\pandoc@box}%
+ \fi%
+}
 % Set default figure placement to htbp
-\makeatletter
 \def\fps@figure{htbp}
 \makeatother
 \ifLuaTeX
@@ -925,11 +927,11 @@ From ``Voyage dans la Lune'' by Georges Melies (1902):
 
 \begin{figure}
 \centering
-\includegraphics{lalune.jpg}
+\pandocbounded{\includegraphics{lalune.jpg}}
 \caption{lalune}
 \end{figure}
 
-Here is a movie \includegraphics{movie.jpg} icon.
+Here is a movie \pandocbounded{\includegraphics{movie.jpg}} icon.
 
 \begin{center}\rule{0.5\linewidth}{0.5pt}\end{center}