[patch] Problems producing TikZ PNGs from LaTeX src blocks (was: Problems producing TikZ PNGs from LaTeX src blocks)

[Benjamin Motz <benni.motz@gmail.com>]

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Eric S Fraga <esflists@gmail.com> writes:

> On Friday, 28 Sep 2018 at 11:39, Christian Moe wrote:
>> Hi,
>>
>> I am trying to generate a PNG file with a TikZ picture from a LaTeX src
>> block, looking at instructions here:
>> https://orgmode.org/worg/org-contrib/babel/languages/ob-doc-LaTeX.html
>>
>> I try this:
>>
>> #+header: :file "tikzpic.png" :fit yes :results raw file :exports results :headers '("\\usepackage{tikz}")
>> #+begin_src latex
>>   \begin{tikzpicture}
>>    \draw [fill=green] (0,4) -- (3,0) -- (-3,0) -- cycle;
>>   \end{tikzpicture}
>> #+end_src

It seems that the function `org-babel-execute:latex' ignores the
property :headers under certain circumstances. Therefore the line
"\usepackage{tikz}" will be missing in your resulting latex document.

The property is not ignored if you also append the property
":imagemagick t" to the #+header line. So you can use the following
header as a fix (for another fix, see below):

#+header: :file "tikzpic.png" :fit yes :results raw file :exports results :headers '("\\usepackage{tikz}") :imagemagick t

I've drafted a patch that fixes the issue. I would appreciate if some
maintainer could have a look and comment, or apply the patch:

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From a54f83d2b411ae58941c32cb23fd47f38e70dc80 Mon Sep 17 00:00:00 2001
From: Benjamin Motz <benjamin.motz@mailbox.org>
Date: Fri, 28 Sep 2018 16:32:59 +0200
Subject: [PATCH 1/2] Fix ob-latex to respect the keyword :headers

This adds support for property :headers in org-format-latex-options.

TINYCHANGE
---
 lisp/ob-latex.el | 8 ++++++--
 lisp/org.el      | 3 +++
 2 files changed, 9 insertions(+), 2 deletions(-)

diff --git a/lisp/ob-latex.el b/lisp/ob-latex.el
index 8d037090e..19e44dee5 100644
--- a/lisp/ob-latex.el
+++ b/lisp/ob-latex.el
@@ -108,8 +108,12 @@ This function is called by `org-babel-execute-src-block'."
 	      (append (cdr (assq :packages params)) org-latex-packages-alist)))
         (cond
          ((and (string-suffix-p ".png" out-file) (not imagemagick))
-          (org-create-formula-image
-           body out-file org-format-latex-options in-buffer))
+	  (let ((latex-options (copy-tree org-format-latex-options)))
+	    (when headers
+	      (plist-put latex-options :headers
+			 (append (plist-get latex-options :headers) headers)))
+            (org-create-formula-image
+             body out-file latex-options in-buffer)))
          ((string-suffix-p ".tikz" out-file)
 	  (when (file-exists-p out-file) (delete-file out-file))
 	  (with-temp-file out-file
diff --git a/lisp/org.el b/lisp/org.el
index f3a19d643..d2ff4e41c 100644
--- a/lisp/org.el
+++ b/lisp/org.el
@@ -18571,6 +18571,9 @@ a HTML file."
 			   (if (string= bg "Transparent") "white" bg))))
 	       (with-temp-file texfile
 		 (insert latex-header)
+		 (when-let ((headers (plist-get options :headers)))
+		   (dolist (h headers)
+		     (insert h)))
 		 (insert "\n\\begin{document}\n"
 			 "\\definecolor{fg}{rgb}{" fg "}\n"
 			 "\\definecolor{bg}{rgb}{" bg "}\n"
-- 
2.18.0


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> This works for me, cutting and pasting exactly what you have posted into a small org file.

You probably have "\\usepackage{tikz}" set in your variable
`org-format-latex-header' (another fix for the issue).

> Output from my *Messages* buffer:
> ,----
> | Wrote /tmp/x.org
> | org-babel-exp process latex at position 128...
> | Evaluate this latex code block on your system? (y or n) y
> | executing Latex code block...
> | (Shell command succeeded with no output)
> | Code block evaluation complete.
> | Local Ispell dictionary set to british
> | Saving file /tmp/x.tex...
> `----
> when I export to LaTeX.  What does your message log say?

Actually, the output looks identical when the command indeed fails to
run latex without errors - the output file is generated nonetheless and
the user thinks everything is ok. I'd suggest to add '-halt-on-error' to
avoid creating an output file. This will then signal an error to the
user. A possible patch is appended:

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From 9f08a34c7eddfea394b9a1e78d54b3b26b139b51 Mon Sep 17 00:00:00 2001
From: Benjamin Motz <benjamin.motz@mailbox.org>
Date: Sat, 29 Sep 2018 22:15:39 +0200
Subject: [PATCH 2/2] preview-latex: don't produce output file on error

This will result in an error-message visible to the user. Otherwise,
the user might just assume that everything went ok, even though there
were issues when creating the output file.

TINYCHANGE
---
 lisp/org.el | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/lisp/org.el b/lisp/org.el
index d2ff4e41c..0c7358eb0 100644
--- a/lisp/org.el
+++ b/lisp/org.el
@@ -3939,7 +3939,7 @@ All available processes and theirs documents can be found in
      :image-input-type "dvi"
      :image-output-type "png"
      :image-size-adjust (1.0 . 1.0)
-     :latex-compiler ("latex -interaction nonstopmode -output-directory %o %f")
+     :latex-compiler ("latex -interaction nonstopmode -halt-on-error -output-directory %o %f")
      :image-converter ("dvipng -fg %F -bg %B -D %D -T tight -o %O %f"))
     (dvisvgm
      :programs ("latex" "dvisvgm")
@@ -3949,7 +3949,7 @@ All available processes and theirs documents can be found in
      :image-input-type "dvi"
      :image-output-type "svg"
      :image-size-adjust (1.7 . 1.5)
-     :latex-compiler ("latex -interaction nonstopmode -output-directory %o %f")
+     :latex-compiler ("latex -interaction nonstopmode -halt-on-error -output-directory %o %f")
      :image-converter ("dvisvgm %f -n -b min -c %S -o %O"))
     (imagemagick
      :programs ("latex" "convert")
@@ -3959,7 +3959,7 @@ All available processes and theirs documents can be found in
      :image-input-type "pdf"
      :image-output-type "png"
      :image-size-adjust (1.0 . 1.0)
-     :latex-compiler ("pdflatex -interaction nonstopmode -output-directory %o %f")
+     :latex-compiler ("pdflatex -interaction nonstopmode -halt-on-error -output-directory %o %f")
      :image-converter
      ("convert -density %D -trim -antialias %f -quality 100 %O")))
   "Definitions of external processes for LaTeX previewing.
-- 
2.18.0


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Best regards,
Benjamin