Developer forum

Where do you use <!--@Gallery.Image.Metadata.title-->? If you just use it in the title attribute (if it's defined) then it will be used as the lightbox title:

<a href="<!--@Gallery.Image.Thumb.Large.Path-->" rel="lightbox[img]" title="<!--@If Defined(Gallery.Image.Metadata.title)--><!--@Gallery.Image.Metadata.title--><!--@Else--><!--@Gallery.Image.Name--><!--@EndIf-->"

Otherwise, you can add it to a custom data attribute

<a href="<!--@Gallery.Image.Thumb.Large.Path-->" rel="lightbox[img]" title="<!--@Gallery.Image.Name-->" data-metadata-title="<!--@If Defined(Gallery.Image.Metadata.title)--><!--@Gallery.Image.Metadata.title--><!--@EndIf-->">

and then change lightbox.js to use the data-metadata-title attribute if it's non-empty and use the title attribute otherwise. 

In lightbox.js you have to change the line

this.imageArray.push([imageLink.href, imageLink.title]);

to

// Use data-metadata-title attribute as title if set. Otherwise, use title attribute
this.imageArray.push([imageLink.href, imageLink.getAttribute('data-metadata-title') ? imageLink.getAttribute('data-metadata-title') : imageLink.title]);

and change the line

return [anchor.href, anchor.title];

to

return [anchor.href, anchor.getAttribute('data-metadata-title') ? anchor.getAttribute('data-metadata-title') : imageLink.title];

I hope it makes sense.

Best regards,
Mikkel