[LyX/2.3.x] Fix bug #11780.

[Richard Kimberly Heck]

commit 429d2171b15a6bea964c203a9b22e257e8496278
Author: Richard Kimberly Heck <rikiheck at lyx.org>
Date:   Sat Mar 14 18:31:25 2020 -0400

    Fix bug #11780.
    
    The preamble snippets are for LaTeX and do not need to be output
    with HTML.
    
    (cherry picked from commit f044d3a3595912415806707582e8aa6b0890bbe7)
---
 src/Buffer.cpp      |    4 ----
 src/LaTeXFeatures.h |    3 ++-
 status.23x          |    1 +
 3 files changed, 3 insertions(+), 5 deletions(-)

diff --git a/src/Buffer.cpp b/src/Buffer.cpp
index 92c3d5d..4c43acb 100644
--- a/src/Buffer.cpp
+++ b/src/Buffer.cpp
@@ -2208,10 +2208,6 @@ void Buffer::writeLyXHTMLSource(odocstream & os,
 		if (!styles.empty())
 			os << "\n<!-- Text Class Preamble -->\n" << styles << '\n';
 
-		styles = features.getPreambleSnippets().str;
-		if (!styles.empty())
-			os << "\n<!-- Preamble Snippets -->\n" << styles << '\n';
-
 		// we will collect CSS information in a stream, and then output it
 		// either here, as part of the header, or else in a separate file.
 		odocstringstream css;
diff --git a/src/LaTeXFeatures.h b/src/LaTeXFeatures.h
index 85f3771..7353f0c 100644
--- a/src/LaTeXFeatures.h
+++ b/src/LaTeXFeatures.h
@@ -95,7 +95,8 @@ public:
 	void addPreambleSnippet(docstring const & snippet, bool allowdupes = false);
 	///
 	TexString getPreambleSnippets() const;
-	///
+	/// Adds CSS information for HTML export.
+	/// Note that addPreambleSnippet is for LaTeX-type export
 	void addCSSSnippet(std::string const &);
 	///
 	docstring getCSSSnippets() const;
diff --git a/status.23x b/status.23x
index 6b30e90..3fbb135 100644
--- a/status.23x
+++ b/status.23x
@@ -91,6 +91,7 @@ What's new
 
 * LYXHTML
 
+- Don't output LaTeX preamble snippets with HTML (bug 11780).
 
 
 * ADVANCED FIND AND REPLACE