ZRenderAbsImage

ZRenderer absolute_image Example

Suppose you were working with a web designer, who knew very little about Zope and less about DTML. They might provide you with HTML pages full of tags like:

    <img src="images/larch">

Suppose you plan to load into folder /Project1/images all of the images which the designer placed in their local images directory. You really don't want to leave the src references relative, since this kills caching, and you'd like to take advantage of the features of the Zope Image class. You might edit the HTML in a number of ways (all of what follows assumes PathNameTraversal for simplicity):

    1. <img src="/Project1/images/larch">  (literal URL)
    2. <img src="&dtml.url-images/larch;"> (using acquisition)
    3. &dtml-images/larch; (acquire and let it render itself)

Now suppose that you need the designer to make further changes to the HTML. Unless you back out all of your edits, the designer will have a hard time, and in any case you'll have to hand edit their changes. If you did 1. or 2., they will see a broken image. 2. and 3. may confuse the HTML editor, and 3. doesn't even contain an img tag any more.

With ZRenderer implemented, they (or you) would add an attribute to all of the image tags:

    <img src="images/larch" z-render=absolute_image>

You would write (or have written) an absolute_image which reads the src attribute of the tag, uses it to look up the Image object, and returns the new tag generated by the Image. Something like this:

    <dtml-var expr="_[tag.src]()">

Then, unless the designer's editor is brain-dead enough to strip out attributes it doesn't recognize, you can send this HTML back and forth and have it work unmodified in both environments.

If you wanted, you could even add more complex behaviors to ZRendered images, such as automatic image rollovers, generated links, or anything else you can compute in your method.