From a90ff2fb192c68d1a380b59b55b394cee57c7ee1 Mon Sep 17 00:00:00 2001
From: Michael Orlitzky <michael@orlitzky.com>
Date: Sat, 14 Oct 2023 13:13:45 -0400
Subject: [PATCH] src/svgtiny_css.c: implement node_is_link() select handler

---
 src/svgtiny_css.c | 56 +++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 56 insertions(+)

diff --git a/src/svgtiny_css.c b/src/svgtiny_css.c
index ebf432d..fec0ed4 100644
--- a/src/svgtiny_css.c
+++ b/src/svgtiny_css.c
@@ -46,6 +46,7 @@ static css_error node_is_root(void *pw, void *node, bool *match);
 static css_error node_count_siblings(void *pw, void *node,
 		bool same_name, bool after, int32_t *count);
 static css_error node_is_empty(void *pw, void *node, bool *is_empty);
+static css_error node_is_link(void *pw, void *node, bool *is_link);
 
 
 /**
@@ -1426,3 +1427,58 @@ css_error node_is_empty(void *pw, void *node, bool *is_empty)
 
 	return CSS_OK;
 }
+
+
+/**
+ * Determine whether or not the given node is a link
+ *
+ * A node is a link if it is an element node whose name is "a" and if
+ * it has an "href" attribute (case-sensitive). This selector
+ * corresponds to node:link pseudo-class in CSS.
+ *
+ * This pseudo-class is a bit awkward because the two standards (HTML5
+ * and CSS) disagree on what it means, and because libsvgtiny does not
+ * have enough information to determine if a link has been "visited"
+ * yet -- that's a UI property. CSS says that :link is for unvisited
+ * links, which we can't determine. HTML5 says that each link must
+ * be either a :link or :visited. Since we can't decide either way,
+ * It seems less wrong to declare that all links are unvisited; i.e.
+ * that they match :link.
+ *
+ * \param pw          Pointer to the current SVG parser state
+ * \param node        Libdom SVG node to check
+ * \param is_link     Pointer to the boolean return value
+ *
+ * \return CSS_OK on success, or CSS_NOMEM if anything goes wrong
+ */
+css_error node_is_link(void *pw, void *node, bool *is_link)
+{
+	dom_exception exc;
+	dom_node *dnode; /* node, but with the right type */
+	dom_string *dnode_name;
+	bool has_href;
+	struct svgtiny_parse_state* state;
+
+	dnode = (dom_node *)node;
+	dnode_name = NULL;
+	has_href = false; /* assume no href attribute */
+	*is_link = false; /* assume that it's not a link */
+
+	exc = dom_node_get_node_name(dnode, &dnode_name);
+	if ((exc != DOM_NO_ERR) || (dnode_name == NULL)) {
+		return CSS_NOMEM;
+	}
+
+	state = (struct svgtiny_parse_state *)pw;
+	if (dom_string_isequal(dnode_name, state->interned_a)) {
+		exc = dom_element_has_attribute(node,
+					state->interned_href,
+					&has_href);
+		if (exc == DOM_NO_ERR && has_href) {
+			*is_link = true;
+		}
+	}
+
+	dom_string_unref(dnode_name);
+	return CSS_OK;
+}
-- 
2.44.2