Use CMake's built-in timestamp formatting (#1242)

* Use CMake's built-in timestamp formatting.

It notably honors SOURCE_DATE_EPOCH if set, making for reproducible
output.  For even better reproducibility, use UTC.  (Unlike the date
command's output, the result is already always in English.)  Extend
this approach to the book, introducing appropriately formatted
PDF_DATE and TODAY variables for its PDF metadata and title page
respectively and making make_pdf configurable.

Under the traditional build system, don't attempt to handle
SOURCE_DATE_EPOCH because date's portable interface is too limited,
just supply PDF_DATE and TODAY values corresponding to the current
date (and time zone) and use the C (English) locale for month names
and abbreviations.

* Fix missing parts and a syntax error in documentation/Makefile

- documentation/Makefile:
  - add make_pdf to target 'clean'
  - add make_pdf to dependencies of 'refman.pdf'
  - add missing quotes to `date` command

- documentation/.gitignore: add make_pdf

---------

Co-authored-by: Albrecht Schlosser <albrechts.fltk@online.de>

documentation/.gitignore

@@ -27,6 +27,7 @@ fluid.z
 generated.dox
 html
 latex
+make_pdf
 sudoku.0
 sudoku.6
 sudoku.z

documentation/CMakeLists.txt

@@ -37,16 +37,12 @@ if(GENERATE_DOCS)
 
   # create required variables
 
-  execute_process(COMMAND date "+%Y"
+  string(TIMESTAMP YEAR "%Y" UTC)
-    OUTPUT_VARIABLE YEAR
-    OUTPUT_STRIP_TRAILING_WHITESPACE
-  )
-
   # note: current locale is used for abbreviated month
-  execute_process(COMMAND date "+%b %d, %Y"
+  string(TIMESTAMP CURRENT_DATE "%b %d, %Y" UTC)
-    OUTPUT_VARIABLE CURRENT_DATE
+  string(TIMESTAMP PDF_DATE "D:%Y%m%d%H%M%SZ" UTC)
-    OUTPUT_STRIP_TRAILING_WHITESPACE
+  string(TIMESTAMP TODAY "%B %d, %Y" UTC)
-  )
+  string(REPLACE " 0" " " TODAY "${TODAY}")
 
   # Find "short" doxygen version if it was built from Git
   # Note: this is still needed in CMake 3.15 but later CMake versions
@@ -77,6 +73,8 @@ if(GENERATE_DOCS)
   if(0) # debug
     fl_debug_var(YEAR)
     fl_debug_var(CURRENT_DATE)
+    fl_debug_var(PDF_DATE)
+    fl_debug_var(TODAY)
     fl_debug_var(FLTK_GIT_REVISION)
     fl_debug_var(DOXYGEN_FOUND)
     fl_debug_var(DOXYGEN_EXECUTABLE)
@@ -179,7 +177,7 @@ if(FLTK_BUILD_PDF_DOCS)
     COMMENT "Converting ${DOXYFILE} to doxygen version ${DOXYGEN_VERSION_SHORT}" VERBATIM
   )
 
-  # generate LaTeX title fltk-title.tex
+  # generate LaTeX title fltk-title.tex and make_pdf script
 
   configure_file(
     ${CMAKE_CURRENT_SOURCE_DIR}/src/fltk-title.tex.in
@@ -187,6 +185,12 @@ if(FLTK_BUILD_PDF_DOCS)
     @ONLY
   )
 
+  configure_file(
+    ${CMAKE_CURRENT_SOURCE_DIR}/make_pdf.in
+    ${CMAKE_CURRENT_BINARY_DIR}/make_pdf
+    @ONLY
+  )
+
   # generate fltk.pdf
 
   add_custom_command(
@@ -196,7 +200,7 @@ if(FLTK_BUILD_PDF_DOCS)
             ${CMAKE_CURRENT_BINARY_DIR}/fltk-title.tex
             ${CMAKE_CURRENT_BINARY_DIR}/fltk-book.tex
     COMMAND ${DOXYGEN_EXECUTABLE} ${DOXYFILE}
-    COMMAND ${CMAKE_CURRENT_SOURCE_DIR}/make_pdf
+    COMMAND ${CMAKE_CURRENT_BINARY_DIR}/make_pdf
     COMMAND cp -f latex/refman.pdf fltk.pdf
     DEPENDS ${CMAKE_CURRENT_BINARY_DIR}/${DOXYFILE}
             ${CMAKE_CURRENT_BINARY_DIR}/fltk-title.tex

documentation/Makefile

@@ -85,7 +85,7 @@ debug_git_rev:
 
 clean:
 	$(RM) Doxyfile Doxybook
-	$(RM) copyright.dox generated.dox
+	$(RM) copyright.dox generated.dox make_pdf
 	$(RM) fltk.pdf refman.pdf src/fltk-title.tex src/fltk-book.tex.in src/fltk-book.tex
 	$(RMDIR) html latex
 	$(RM) *~ *.bck *.bak *.log
@@ -211,15 +211,24 @@ html:	$(HTMLFILES) Doxyfile
 pdf:	refman.pdf
 	cp -f latex/refman.pdf fltk.pdf
 
-refman.pdf: $(HTMLFILES) Doxybook src/fltk-book.tex
+refman.pdf: $(HTMLFILES) Doxybook src/fltk-book.tex make_pdf
 	-$(RMDIR) latex
 	echo "Generating PDF documentation ..."
 	"$(DOXYDOC)" Doxybook
 	./make_pdf
 
+make_pdf: make_pdf.in
+	echo "Generating $@ ..."
+	PDF_DATE=`date +D:%Y%m%d%H%M%S`; \
+	sed -e"s/@PDF_DATE@/$$PDF_DATE/g" \
+	    < $< > $@
+	chmod +x $@
+
 src/fltk-title.tex: src/fltk-title.tex.in
 	echo "Generating $@ ..."
+	TODAY=`LC_ALL=C date '+%B %e, %Y'`; \
 	sed -e"s/@FLTK_GIT_REVISION@/$(FLTK_GIT_REVISION)/g" \
+	    -e"s/@TODAY@/$$TODAY/g" \
 	    < $< > $@
 
 src/fltk-book.tex.in: src/fltk-title.tex
@@ -237,7 +246,7 @@ src/fltk-book.tex: src/fltk-book.tex.in
 
 generated.dox: generated.dox.in
 	echo "Generating $@ ..."
-	CURRENT_DATE=`date "+%b %d, %Y"`; \
+	CURRENT_DATE=`LC_ALL=C date "+%b %d, %Y"`; \
 	DOXYGEN_VERSION_SHORT=`"$(DOXYDOC)" --version|cut -f1 -d' '`; \
 	sed -e"s/@CURRENT_DATE@/$$CURRENT_DATE/g" \
 	    -e"s/@FLTK_GIT_REVISION@/$(FLTK_GIT_REVISION)/g" \

documentation/make_pdf.in

@@ -26,10 +26,15 @@
 #
 # Used in: Makefile and CMakeLists.txt
 
+run_pdflatex() {
+  pdflatex --interaction=nonstopmode \
+    "\pdfinfo{/CreationDate(@PDF_DATE@)/ModDate(@PDF_DATE@)}\input{refman.tex}"
+}
+
 ( cd latex
-  pdflatex --interaction=nonstopmode refman.tex
+  run_pdflatex
   makeindex refman.idx
-  pdflatex --interaction=nonstopmode refman.tex
+  run_pdflatex
   latex_count=5
   while egrep -s 'Rerun (LaTeX|to get cross-references right)' refman.log \
 	  && [ $latex_count -gt 0 ]

documentation/src/fltk-title.tex.in

@@ -25,7 +25,7 @@ provided this copyright and permission notice are preserved.}\\
 \vspace*{1.5cm}
 {\large Generated by Doxygen @DOXY_VERSION@}\\
 \vspace*{0.5cm}
-\today{}\\
+@TODAY@\\
 \vspace*{0.5cm}
 {\small Git revision @FLTK_GIT_REVISION@}\\
 \end{center}