src/svgtiny_css.c: implement named_sibling_node() select handler

diff --git a/src/svgtiny_css.c b/src/svgtiny_css.c
index 01b566f93c876ef5f86111b62aa089f614734930..2a59f6cd5adb39c1c5a8dbc41655a345ded561ac 100644 (file)
--- a/src/svgtiny_css.c
+++ b/src/svgtiny_css.c
@@ -9,6 +9,8 @@ static css_error node_classes(void *pw, void *node,
 static css_error node_id(void *pw, void *node, lwc_string **id);
 static css_error named_parent_node(void *pw, void *node,
                const css_qname *qname, void **parent);
+static css_error named_sibling_node(void *pw, void *node,
+               const css_qname *qname, void **sibling);
 
 
 /**
@@ -228,3 +230,94 @@ css_error named_parent_node(void *pw, void *node,
 
        return CSS_OK;
 }
+
+
+/**
+ * Find the "next-sibling" of the given element having the given name
+ *
+ * This search corresponds to the "+ foo" combinator in CSS and will
+ * find only "foo" element nodes that immediately precede the given
+ * node under the same parent in the DOM. In CSS the tree is viewed
+ * top-down and in libdom it is viewed from the bottom-up; as a result
+ * "next" and "previous" are sometimes backwards. This is case-sensitive.
+ *
+ * \param pw       Pointer to the current SVG parser state
+ * \param node     Libdom SVG node
+ * \param qname    Name of the sibling node to search for
+ * \param sibling  Address at which to store the sibling node pointer
+ *
+ * \return Always returns CSS_OK
+ *
+ * \post If a suitable element is found, a pointer to it will be
+ *       stored at the address pointed to by \a sibling; otherwise,
+ *       NULL will be stored at the address pointed to by \a sibling
+ */
+css_error named_sibling_node(void *pw, void *node,
+               const css_qname *qname, void **sibling)
+{
+       UNUSED(pw);
+       dom_node *n = node; /* the current node */
+       dom_node *prev; /* the previous node */
+       dom_exception err;
+       dom_node_type type;
+       dom_string *name;
+
+       *sibling = NULL; /* default to nothing found */
+
+       /* Begin the search; the first iteration we do outside of the
+        * loop. Implementation detil: dom_node_get_previous_sibling()
+        * increments the reference counter on the returned node. A
+        * comment within named_parent_node() explains why we
+        * decrement it ASAP. */
+       err = dom_node_get_previous_sibling(n, &n);
+       if (err != DOM_NO_ERR) {
+               return CSS_OK;
+       }
+
+       while (n != NULL) {
+               /* We're looking for the first ELEMENT sibling */
+               err = dom_node_get_node_type(n, &type);
+               if (err != DOM_NO_ERR) {
+                       dom_node_unref(n);
+                       return CSS_OK;
+               }
+
+               if (type == DOM_ELEMENT_NODE) {
+                       /* We found an element node, does it have the
+                        * right name? */
+                       err = dom_node_get_node_name(n, &name);
+                       if (err != DOM_NO_ERR) {
+                               dom_node_unref(n);
+                               return CSS_OK;
+                       }
+
+                       if (dom_string_lwc_isequal(name,
+                                       qname->name)) {
+                               /* The name is right, return it */
+                               *sibling = n;
+                       }
+
+                       /* There's only one next-sibling element node
+                        * and we've already found it, so if its name
+                        * wasn't right, we return the default value
+                        * of NULL below */
+                       dom_string_unref(name);
+                       dom_node_unref(n);
+                       return CSS_OK;
+               }
+
+               /* Not an element node, so we move on the the previous
+                * previous sibling */
+               err = dom_node_get_previous_sibling(n, &prev);
+               if (err != DOM_NO_ERR) {
+                       dom_node_unref(n);
+                       return CSS_OK;
+               }
+
+               dom_node_unref(n);
+               n = prev;
+       }
+
+       return CSS_OK;
+}
+