[LyX/master] DocBook: improve equation formatting (new lines for block equations).

[Thibaut Cuvelier]

commit 39ad6e84f076cea65f140593e5b6647905219af3
Author: Thibaut Cuvelier <tcuvelier at lyx.org>
Date:   Sat Aug 29 19:05:59 2020 +0200

    DocBook: improve equation formatting (new lines for block equations).
---
 autotests/export/docbook/basic.lyx |    2 +-
 autotests/export/docbook/basic.xml |    9 +++++----
 src/Paragraph.cpp                  |    4 ++--
 src/mathed/InsetMathHull.cpp       |    8 +++++++-
 src/output_docbook.cpp             |   16 +++++++++-------
 5 files changed, 24 insertions(+), 15 deletions(-)

diff --git a/autotests/export/docbook/basic.lyx b/autotests/export/docbook/basic.lyx
index 1735dc4..fa98d65 100644
--- a/autotests/export/docbook/basic.lyx
+++ b/autotests/export/docbook/basic.lyx
@@ -185,7 +185,7 @@ noprefix "false"
 
 \begin_layout Standard
 Also, a formula with an user-defined macro that outputs well in LaTeX but
- cannot in MathML (hence replaced by picture): 
+ cannot in MathML: 
 \begin_inset Formula $\testmacro$
 \end_inset
 
diff --git a/autotests/export/docbook/basic.xml b/autotests/export/docbook/basic.xml
index 7980289..430611e 100644
--- a/autotests/export/docbook/basic.xml
+++ b/autotests/export/docbook/basic.xml
@@ -30,7 +30,7 @@
 </inlineequation>. </para>
 </blockquote>
 <para>Now, we're outside quotes.</para>
-<para><informalequation>
+<informalequation>
 <alt role='tex'>Formula!</alt>
  <m:math>
  
@@ -39,7 +39,8 @@
   </m:mrow>
  </m:mrow>
  </m:math>
-</informalequation><informalequation xml:id="eq.EQ.">
+</informalequation>
+<informalequation xml:id="eq.EQ.">
 <alt role='tex'>\text{I am a formula with a ref.}\label{eq:EQ.}</alt>
  <m:math>
  
@@ -50,9 +51,9 @@
   </m:mstyle>
  </m:mrow>
  </m:math>
-</informalequation></para>
+</informalequation>
 <para>See <xref linkend="sec.Sec-2kqgsdiflhqsdlifgjuzer-povtuizmvnuer-t-vmsrmfli--uh--a--rtpfuo----rtpc.m-ca-rgifzapeu-tvgz" />.</para>
-<para>Also, a formula with an user-defined macro that outputs well in LaTeX but cannot in MathML (hence replaced by picture): <inlineequation>
+<para>Also, a formula with an user-defined macro that outputs well in LaTeX but cannot in MathML: <inlineequation>
 <alt role='tex'>\testmacro</alt>
 <mathphrase>MathML export failed. Please report this as a bug.</mathphrase>
 </inlineequation>. </para>
diff --git a/src/Paragraph.cpp b/src/Paragraph.cpp
index e87ef88..aad1ccf 100644
--- a/src/Paragraph.cpp
+++ b/src/Paragraph.cpp
@@ -3349,7 +3349,8 @@ std::vector<docstring> Paragraph::simpleDocBookOnePar(Buffer const & buf,
 
 	std::vector<docstring> generatedParagraphs;
 	odocstringstream os;
-	auto * xs = new XMLStream(os);
+	auto * xs = new XMLStream(os); // XMLStream has no copy constructor: to create a new object, the only solution
+	// is to hold a pointer to the XMLStream (xs = XMLStream(os) is not allowed once the first object is built).
 
 	// Parsing main loop.
 	for (pos_type i = initial; i < size(); ++i) {
@@ -3361,7 +3362,6 @@ std::vector<docstring> Paragraph::simpleDocBookOnePar(Buffer const & buf,
 		if (getInset(i) != nullptr && getInset(i)->lyxCode() == NEWLINE_CODE) {
 			generatedParagraphs.push_back(os.str());
 			os = odocstringstream();
-			// XMLStream has no copy constructor.
 			delete xs;
 			xs = new XMLStream(os);
 		}
diff --git a/src/mathed/InsetMathHull.cpp b/src/mathed/InsetMathHull.cpp
index 800cbeb..5847121 100644
--- a/src/mathed/InsetMathHull.cpp
+++ b/src/mathed/InsetMathHull.cpp
@@ -2420,10 +2420,16 @@ void InsetMathHull::docbook(XMLStream & xs, OutputParams const & runparams) cons
 	docstring name;
 	if (getType() == hullSimple)
 		name = from_ascii("inlineequation");
-	else
+	else {
+		// This is a block equation, always have <informalequation> on its own line.
+		if (!xs.isLastTagCR())
+			xs << xml::CR();
+
 		name = from_ascii("informalequation");
+	}
 
 	// DocBook also has <equation>, but it comes with a title.
+	// TODO: recognise \tag from amsmath?
 
 	docstring attr;
 	for (row_type i = 0; i < nrows(); ++i) {
diff --git a/src/output_docbook.cpp b/src/output_docbook.cpp
index 9d51853..e609f39 100644
--- a/src/output_docbook.cpp
+++ b/src/output_docbook.cpp
@@ -446,10 +446,16 @@ void makeParagraph(
 			special_case = true;
 	}
 
+	size_t nInsets = std::distance(par->insetList().begin(), par->insetList().end());
+
 	// Plain layouts must be ignored.
-	if (!special_case && buf.params().documentClass().isPlainLayout(par->layout()) && !runparams.docbook_force_pars)
-		special_case = true;
-	// TODO: Could get rid of this with a DocBook equivalent to htmlisblock?
+	special_case |= buf.params().documentClass().isPlainLayout(par->layout()) && !runparams.docbook_force_pars;
+	// Equations do not deserve their own paragraph (DocBook allows them outside paragraphs).
+	special_case |= nInsets == par->size() && std::all_of(par->insetList().begin(), par->insetList().end(), [](InsetList::Element inset) {
+		return inset.inset && inset.inset->asInsetMath();
+	});
+
+	// TODO: Could get rid of this with a DocBook equivalent to htmlisblock? Not for all cases, unfortunately... See above for those that have been determined not to be allowable for this potential refactoring.
 	if (!special_case && par->size() == 1 && par->getInset(0)) {
 		Inset const * firstInset = par->getInset(0);
 
@@ -460,10 +466,6 @@ void makeParagraph(
 		if (!special_case && firstInset->asInsetCommand())
 			special_case = firstInset->asInsetCommand()->params().getCmdName() == "bibtex";
 
-		// Equations do not deserve their own paragraph (DocBook allows them outside paragraphs).
-		if (!special_case && firstInset->asInsetMath())
-			special_case = true;
-
 		// ERTs are in comments, not paragraphs.
 		if (!special_case && firstInset->lyxCode() == lyx::ERT_CODE)
 			special_case = true;