From a35b5ddc3e2513a44374340cd245b046aa084405 Mon Sep 17 00:00:00 2001
From: Zufu Liu <unknown>
Date: Sat, 2 Nov 2019 10:19:22 +1100
Subject: Feature [feature-requests:#1299] Treat custom tags from HTML5 as
 known tags. These contain "-" like "custom-tag".

---
 doc/ScintillaHistory.html |  4 ++++
 lexers/LexHTML.cxx        | 14 ++++++++++++++
 2 files changed, 18 insertions(+)

diff --git a/doc/ScintillaHistory.html b/doc/ScintillaHistory.html
index e9ff2cf58..2c49c8c9f 100644
--- a/doc/ScintillaHistory.html
+++ b/doc/ScintillaHistory.html
@@ -571,6 +571,10 @@
 	<a href="https://sourceforge.net/p/scintilla/feature-requests/1317/">Feature #1317</a>.
 	</li>
 	<li>
+	HTML lexer treats custom tags from HTML5 as known tags. These contain "-" like "custom-tag".
+	<a href="https://sourceforge.net/p/scintilla/feature-requests/1299/">Feature #1299</a>.
+	</li>
+	<li>
 	HTML lexer fixes bug with some non-alphabetic characters in unknown tags.
 	<a href="https://sourceforge.net/p/scintilla/feature-requests/1320/">Feature #1320</a>.
 	</li>
diff --git a/lexers/LexHTML.cxx b/lexers/LexHTML.cxx
index 6b3748859..17c0846aa 100644
--- a/lexers/LexHTML.cxx
+++ b/lexers/LexHTML.cxx
@@ -266,6 +266,18 @@ void classifyAttribHTML(Sci_PositionU start, Sci_PositionU end, const WordList &
 	styler.ColourTo(end, chAttr);
 }
 
+// https://html.spec.whatwg.org/multipage/custom-elements.html#custom-elements-core-concepts
+bool isHTMLCustomElement(const std::string &tag) {
+	// check valid HTML custom element name: starts with an ASCII lower alpha and contains hyphen.
+	if (tag.length() < 2 || !IsLowerCase(tag[0])) {
+		return false;
+	}
+	if (tag.find('-') == std::string::npos) {
+		return false;
+	}
+	return true;
+}
+
 int classifyTagHTML(Sci_PositionU start, Sci_PositionU end,
                            const WordList &keywords, Accessor &styler, bool &tagDontFold,
                     bool caseSensitive, bool isXml, bool allowScripts,
@@ -288,6 +300,8 @@ int classifyTagHTML(Sci_PositionU start, Sci_PositionU end,
 		chAttr = SCE_H_SGML_DEFAULT;
 	} else if (!keywords || keywords.InList(tag.c_str())) {
 		chAttr = SCE_H_TAG;
+	} else if (!isXml && isHTMLCustomElement(tag)) {
+		chAttr = SCE_H_TAG;
 	}
 	if (chAttr != SCE_H_TAGUNKNOWN) {
 		styler.ColourTo(end, chAttr);
-- 
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