Lightbox support for embed-resources

The base 64 image src will be used when the ligthbox is rendered.

Fixes #6892

Author: dragonstyle

src/resources/filters/layout/lightbox.lua

@@ -340,7 +340,25 @@ function lightbox()
           local optionsJson = quarto.json.encode(options)
 
           -- generate the initialization script with the correct options
-          local scriptTag = "<script>var lightboxQuarto = GLightbox(" .. optionsJson .. ");</script>"
+          local scriptContents = "var lightboxQuarto = GLightbox(" .. optionsJson .. ");\n"
+          scriptContents = scriptContents .. [[
+window.onload = () => {
+  lightboxQuarto.on('slide_before_load', (data) => {
+    const { slideIndex, slideNode, slideConfig, player, trigger } = data;
+    const href = trigger.getAttribute('href');
+    if (href !== null) {
+      const imgEl = window.document.querySelector(`a[href="${href}"] img`);
+      if (imgEl !== null) {
+        const srcAttr = imgEl.getAttribute("src");
+        if (srcAttr && srcAttr.startsWith("data:")) {
+          slideConfig.href = srcAttr;
+        }
+      }
+    }
+  });
+};
+          ]]
+          local scriptTag = "<script>" .. scriptContents .. "</script>"
 
           -- inject the rendering code
           quarto.doc.include_text("after-body", scriptTag)