[SalesForce] Render as pdf make static resource images break in Summer 14 pre-release managed package

The way we did this in FinancialForce (as mentioned by eyescream above) was to include the VF page in the managed package, but ensure that the controller and all methods the page called by the page (same with any components you use) were marked as global. So the button defaults to using that VF page, all good.

When the customer wants to override it they clone the page (copy + paste the contents), change the 'c:' references to the package namespace, eg. 'myns:' and save. The page should work as before. Then by having a custom setting defined to override the print VF page to be used we have code behind our print button that checks if there's a value, if there is it constructs the PageReference to redirect to from that (passing in the id of the record to print, so no using Page.PDFPageName), otherwise it uses the managed package version (Page.PDFPageName in your case). So something like this in the controller:

global PageReference getPrintPage()
{
    Id invoiceId = stdController.getId();
    PageReference printPage = Page.PDFPageName;      

    String customPageUrl = MySettings__c.getInstance().CustomPrintPage__c;
    if( !String.isBlank( customPageUrl ) )
    {
        printPage = new PageReference( customPageUrl );
    }

    printPage.getParameters().put( 'id', invoiceId );

    return printPage.setRedirect( true );
}

Your code to attach the PDF to the record (or in our case mark a document as 'Printed') lives in the controller so will still be called by the overridden page since it's using the same controller behind the scenes.

Your problem is caused by static resources in your managed package having to be referenced by their name including the managed package namespace prefix once the managed package is installed.

My recommendation is to put all the resources that have cross-references to each other in the same static resource.

To illustrate, I have Bootstrap CSS and fonts in a zip file that is served via a static resource. The Visualforce contains:

<link href="{!URLFor($Resource.appzip, 'lib/bootstrap/bootstrap.min.css')}" />

and this appears in the HTML (when the managed package that uses namespace cveep has been installed) as:

<link href="/resource/1393499712000/cveep__appzip/lib/bootstrap/bootstrap.min.css" />

So the first part of the path is the versioned and namespace-prefixed static resource name and the rest of the path is the path of the CSS within the static resource zip (i.e. namespace free).

The relevance to your issue is that the CSS contains relative references such as:

src:url('../fonts/glyphicons-halflings-regular.eot')

and these resolve correctly because they are relative and within the part of the path before the namespace prefix and resource timestamp.

An alternate solution is to always include the namespace prefix in your references i.e. [namespacename]png_delete_icon because your namespace org should support that as well as the non-namespaced name. But if you deploy the source code to some other org for say continuous integration testing the path will be wrong there. And scattering the namespace about feels wrong. And if you are using 3rd party CSS like Bootstrap having to edit that would be painful.