PDF: Allow style elements inside inlined SVGs

Some SVG files contain style elements. These need to remain inside the html that is sent to Flying Saucer, so that Apache Batik can pick them up.

Fixes: SE-13745

src/main/java/sirius/web/templates/pdf/TagliatellePDFContentHandler.java

@@ -10,6 +10,7 @@
 
 import org.jsoup.Jsoup;
 import org.jsoup.nodes.Document;
+import org.jsoup.nodes.Element;
 import org.jsoup.nodes.Entities;
 import org.xhtmlrenderer.pdf.ITextRenderer;
 import sirius.kernel.di.std.Part;
@@ -21,6 +22,7 @@
 import sirius.web.templates.TagliatelleContentHandler;
 
 import java.io.OutputStream;
+import java.util.function.Predicate;
 
 /**
  * Generates a PDF output by evaluating a given tagliatelle template which must result in a valid XHTML dom.
@@ -85,17 +87,25 @@ private String cleanHtml(String html) {
             document.head().appendChild(bookmarks);
         });
 
-        // in theory, the following two lines should be possible with a single CSS selector; however, in practice, Jsoup
-        // does not select the style elements correctly when attempting that
         document.select("script").remove();
-        document.select("body style").remove();
+        document.select("body style").removeIf(Predicate.not(this::isElementInsideSvg));
 
         document.outputSettings().syntax(Document.OutputSettings.Syntax.xml);
         document.outputSettings().escapeMode(Entities.EscapeMode.xhtml);
         document.outputSettings().charset("UTF-8");
         return document.html();
     }
 
+    /**
+     * Determine whether the given element is part of an SVG element by checking all ancestors.
+     *
+     * @param element the element to check
+     * @return <tt>true</tt> if the element is part of an SVG, <tt>false</tt> otherwise
+     */
+    private boolean isElementInsideSvg(Element element) {
+        return element.closest("svg") != null;
+    }
+
     @Override
     public int getPriority() {
         return DEFAULT_PRIORITY;