From 7aef4c19dd9b4b9da2460e22395b6a25a476100f Mon Sep 17 00:00:00 2001
From: Shulhan <ms@kilabit.info>
Date: Fri, 18 Apr 2025 19:35:03 +0700
Subject: all: fix the logic when applying default embedded CSS

By default, the document contains ":stylesheet:" attribute, which
means using the default embedded CSS.
To disable it, unset the attribute using ":stylesheet!:".
To overwrite it, set the attribute to path of CSS file
":stylesheet: my.css".

While at it, export the DocAttrStylesheet.
---
 document.go           |  4 ++--
 document_attribute.go | 10 ++++++++--
 2 files changed, 10 insertions(+), 4 deletions(-)

diff --git a/document.go b/document.go
index aa89434..1fa88ed 100644
--- a/document.go
+++ b/document.go
@@ -215,8 +215,8 @@ func (doc *Document) ToHTML(out io.Writer) (err error) {
 
 	var ok bool
 
-	_, ok = doc.Attributes.Entry[docAttrStylesheet]
-	if ok {
+	docAttrValue, ok = doc.Attributes.Entry[DocAttrStylesheet]
+	if ok && len(docAttrValue) == 0 {
 		buf.WriteByte('\n')
 		buf.WriteString(_defaultCSS)
 	}
diff --git a/document_attribute.go b/document_attribute.go
index 9419084..3217c16 100644
--- a/document_attribute.go
+++ b/document_attribute.go
@@ -11,6 +11,13 @@ const (
 	DocAttrGenerator   = `generator`
 	DocAttrKeywords    = `keywords`
 
+	// By default, the document contains ":stylesheet:" attribute, which
+	// means using the default embedded CSS.
+	// To disable it, unset the attribute using ":stylesheet!:".
+	// To overwrite it, set the attribute to path of CSS file
+	// ":stylesheet: my.css".
+	DocAttrStylesheet = `stylesheet`
+
 	docAttrAuthorInitials  = `authorinitials`
 	docAttrDocdir          = `docdir`
 	docAttrDocTitle        = `doctitle`
@@ -36,7 +43,6 @@ const (
 	docAttrSectNumLevel    = `sectnumlevels`
 	docAttrSectNums        = `sectnums`
 	docAttrShowTitle       = `showtitle`
-	docAttrStylesheet      = `stylesheet`
 	docAttrTOC             = `toc`
 	docAttrTOCLevels       = `toclevels`
 	docAttrTOCTitle        = `toc-title`
@@ -70,7 +76,7 @@ func newDocumentAttribute() DocumentAttribute {
 			docAttrLastUpdateValue: ``,
 			docAttrSectIDs:         ``,
 			docAttrShowTitle:       ``,
-			docAttrStylesheet:      ``,
+			DocAttrStylesheet:      ``, // Default to embedded CSS.
 			docAttrTableCaption:    ``,
 			docAttrVersionLabel:    ``,
 		},
-- 
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