css: add isEmptyText in node interface

src/css/libdom.zig

@@ -61,6 +61,14 @@ pub const Node = struct {
         return t == .text;
     }
 
+    pub fn isEmptyText(n: Node) !bool {
+        const data = try parser.nodeTextContent(n.node);
+        if (data == null) return true;
+        if (data.?.len == 0) return true;
+
+        return std.mem.trim(u8, data.?, &std.ascii.whitespace).len == 0;
+    }
+
     pub fn tag(n: Node) ![]const u8 {
         return try parser.nodeName(n.node);
     }

src/css/match_test.zig

@@ -48,6 +48,10 @@ pub const Node = struct {
         return false;
     }
 
+    pub fn isEmptyText(_: *const Node) !bool {
+        return false;
+    }
+
     pub fn tag(n: *const Node) ![]const u8 {
         return n.name;
     }

src/css/selector.zig

@@ -383,8 +383,10 @@ pub const Selector = union(enum) {
                         while (c != null) {
                             if (c.?.isElement()) return false;
 
-                            // TODO check text node content equals an empty
-                            // string ("")
+                            if (c.?.isText()) {
+                                if (try c.?.isEmptyText()) continue;
+                                return false;
+                            }
 
                             c = try c.?.nextSibling();
                         }