From 9b9d12ce99592074cac6875fd4cfcb2b73f87330 Mon Sep 17 00:00:00 2001
From: Gerard Vermeulen <gerard.vermeulen@neel.cnrs.fr>
Date: Wed, 5 Jan 2022 17:37:03 +0100
Subject: [PATCH] Fix Worg image export trick for Emacs-27.2 and Org-9.5.2

---
 .gitignore |  2 ++
 README.org | 56 ++++++++++++++++++++++++++++++++++++++++++++++++++++++
 2 files changed, 58 insertions(+)

diff --git a/.gitignore b/.gitignore
index b1c34c7..3784151 100644
--- a/.gitignore
+++ b/.gitignore
@@ -20,6 +20,8 @@
 latexmkrc
 org-store-link
 setup-include.org
+tree.svg
+worg-backend-dependent-execution-update.org
 
 /_minted-README
 /eln-cache
diff --git a/README.org b/README.org
index 9c2a6bf..4d181d6 100644
--- a/README.org
+++ b/README.org
@@ -1556,6 +1556,62 @@ Listing [[lst:emacs-lisp-setup-call]] initializes the buffer local variables
   \end{titlepage}
 #+end_src
 
+*** [[https://orgmode.org/worg/org-contrib/babel/languages/ob-doc-LaTeX.html#orgcc214c1][Worg: backend dependent execution]]
+:PROPERTIES:
+:CUSTOM_ID: sec:backend-dependent-execution-update
+:END:
+
+#+caption[Worg update: backend dependent header arguments]:
+#+caption: Worg update: backend dependent header arguments.
+#+name: lst:backend-dependent-execution-update
+#+begin_src org :tangle worg-backend-dependent-execution-update.org
+  ,#+latex_header: \usepackage{tikz}
+
+  ,#+header: :file (by-backend (html "tree.svg") (latex nil))
+  ,#+header: :results (by-backend (html "raw file") (latex "latex replace"))
+  ,#+header: :headers '("\\usepackage{tikz}\n")
+  ,#+begin_src latex
+    \usetikzlibrary{trees}
+    \begin{tikzpicture}
+      \node [circle, draw, fill=red!20] at (0,0) {1}
+      child { node [circle, draw, fill=blue!30] {2}
+        child { node [circle, draw, fill=green!30] {3} }
+        child { node [circle, draw, fill=yellow!30] {4} }};
+    \end{tikzpicture}
+  ,#+end_src
+
+  ,* COMMENT Setup
+  ,#+begin_src emacs-lisp
+    (with-eval-after-load 'ox
+      (setq org-babel-latex-htlatex "htlatex")
+      (defmacro by-backend (&rest body)
+        `(cl-case org-export-current-backend ,@body)))
+  ,#+end_src
+#+end_src
+
+#+caption[Specify export backend dependent header arguments]:
+#+caption: Specify export backend dependent header arguments.
+#+name: lst:header-arguments-by-backend
+#+begin_src emacs-lisp
+  (with-eval-after-load 'ox
+    (defmacro by-backend (&rest body)
+      `(cl-case org-export-current-backend ,@body)))
+#+end_src
+
+This section updates the outdated [[https://orgmode.org/worg/org-contrib/babel/languages/ob-doc-LaTeX.html#orgcc214c1][Worg: backend dependent execution]] example to
+Emacs-27.2 and Org-9.5.2.  It shows how to export [[https://en.wikipedia.org/wiki/PGF/TikZ][PGF/TikZ]] images to:
+1. [[https://en.wikipedia.org/wiki/PDF][PDF]] by embedding in [[https://www.latex-project.org/][LaTeX]].
+2. [[https://en.wikipedia.org/wiki/HTML][HTML]] by passing from [[https://www.latex-project.org/][LaTeX]] by [[https://en.wikipedia.org/wiki/PDF][PDF]] and to [[https://en.wikipedia.org/wiki/Scalable_Vector_Graphics][SVG]].
+Listing [[lst:backend-dependent-execution-update]] tangles to
+[[file:worg-backend-dependent-execution-update.org][worg-backend-dependent-execution-update.org]] as either a standalone example or an
+example for inclusion. Listing [[lst:header-arguments-by-backend]] tangles to the
+=user-init-file= to make the convenience =by-backend= macro always available.
+Finally, inclusion of [[file:worg-backend-dependent-execution-update.org][worg-backend-dependent-execution-update.org]] produces here
+the figure with the nodes 1, 2, 3, and 4:\\
+
+#+include: worg-backend-dependent-execution-update.org
+*This line is hidden because of the "{{{*}}}COMMENT Setup" header in the inclusion!*
+
 * Programming
 :PROPERTIES:
 :CUSTOM_ID: sec:programming