lightbox - honor existing window.onload handlers. Closes #9727

Author: cscheid

src/resources/filters/layout/lightbox.lua

@@ -381,29 +381,36 @@ function lightbox()
           -- generate the initialization script with the correct options
           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="${href}"] img`);
-      if (imgEl !== null) {
-        const srcAttr = imgEl.getAttribute("src");
-        if (srcAttr && srcAttr.startsWith("data:")) {
-          slideConfig.href = srcAttr;
+(function() {
+  let previousOnload = window.onload;
+  window.onload = () => {
+    if (previousOnload) {
+      previousOnload();
+    }
+    lightboxQuarto.on('slide_before_load', (data) => {
+      const { slideIndex, slideNode, slideConfig, player, trigger } = data;
+      const href = trigger.getAttribute('href');
+      if (href !== null) {
+        const imgEl = window.document.querySelector(`a[href="${href}"] img`);
+        if (imgEl !== null) {
+          const srcAttr = imgEl.getAttribute("src");
+          if (srcAttr && srcAttr.startsWith("data:")) {
+            slideConfig.href = srcAttr;
+          }
         }
+      } 
+    });
+  
+    lightboxQuarto.on('slide_after_load', (data) => {
+      const { slideIndex, slideNode, slideConfig, player, trigger } = data;
+      if (window.Quarto?.typesetMath) {
+        window.Quarto.typesetMath(slideNode);
       }
-    } 
-  });
-
-  lightboxQuarto.on('slide_after_load', (data) => {
-    const { slideIndex, slideNode, slideConfig, player, trigger } = data;
-    if (window.Quarto?.typesetMath) {
-      window.Quarto.typesetMath(slideNode);
-    }
-  });
-
-};
+    });
+  
+  };
+  
+})();
           ]]
           local scriptTag = "<script>" .. scriptContents .. "</script>"