Migrating Zope product code

The following list shows a few common migration issues independent of the Python version used.

Changed import paths

Several commonly used Zope code modules have moved. Here’s a short list of corrections you will have to make in your code. Many of these changed paths have already existed under Zope 2, so you can make those corrections ahead of time.

from Globals import InitializeClass  # OLD
from AccessControl.class_init import InitializeClass  # NEW

implementer versus implements

How to signal that a class implements a specific interface has moved from a function called at class level into a class decorator and changed its name:

from zope.interface import implementer
from zope.interface import implements
from .interfaces import IMyClass

class MyClass:
    implements(IMyClass)  # OLD

@implementer(IMyClass)  # NEW
class AnotherClass:

Migrating to the new bootstrap-based ZMI

Since Zope 4.0b6 the ZMI is styled using Bootstrap. The previously used GIF icons were replaced by font glyphs which are stored in the package zmi.styles (part of Zope) together with the CSS and JavaScript needed by Bootstrap.

The free Font Awesome glyphs are used as icons, see the table of available icons.

Update existing package code

If you have a Product or package which contains types, which can be added via the ZMI, the default icon will be shown.

To use one of the new icons add an attribute named zmi_icon to the class. As value use a name listed on available icons prefixed by fas fa-. Example to use the info icon (i in a circle):

zmi_icon = 'fas fa-info-circle'

A few Zope products provide content that can be added in the ZMI without showing a dialog to collect data such as an id or title. These will now default to showing the new modal dialog as well. You can prevent that by adding another class variable:

zmi_show_add_dialog = False

Custom icons and resources

To use custom icons (which are not part of zmi.styles) or load custom CSS resp. JavaScript, you have to:

  1. create a directory and fill it with your assets

  2. register this directory as resource directory

  3. register a subscription adapter for App.interfaces.ICSSPaths resp. App.interfaces.IJSPaths. This adapter has to return an iterable of paths resp. URLs which should be loaded when rendering the ZMI.

Example taken from zmi.styles:

  • Register the resource directory via ZCML:

        directory="resources" />
  • Create a subscription adapter returning the path to the CSS file (zmi.styles has this code in subscriber.py.):

    import zope.component
    import zope.interface
    def css_paths(context):
        """Return paths to CSS files needed for the Zope 4 ZMI."""
        return (
  • Register the subscriber via ZCML:

        factory=".subscriber.css_paths" />

Use custom resources via ZMI

To add custom CSS or JavaScript resources via ZMI you have to add a property:

  • zmi_additional_css_paths for additional CSS

  • zmi_additional_js_paths for additional JavaScript

The properties can have one of the following types:

  • string

  • ustring

  • ulines

The value of the property has to be one or more paths/URLs to CSS resp. JavaScript which will be included in the HTML of the ZMI. (Paths have to be resolvable by the browser aka not simple file system paths.)

Update existing Zope 2 ZMI templates

The old Zope 2 styling rules did not allow a modern and responsive design. Now the Zope 4 ZMI uses some basic CSS class names of the bootstrap CSS framework and structuring concepts for page layout and forms. A ZMI page usually sequences following templates nesting the page core:

  1. manage_page_header()

  2. manage_tabs()

  3. page core

  4. manage_page_footer()

The page core of any form or object listing ZMI template is starting by the html element <main class="container-fluid">. Usually <main> is nesting a p element for a help-text and the actual form. To make specific form styling possible the form-element has following CSS names:

  1. zmi-$classname

  2. zmi-edit|-add

In general specific functional ZMI elements are declared by a CSS class with a prefixed zmi- whereas the basic layout is done by usual bootstrap classes following the typical element nesting: any form element has a bootstrap-like form-group structure containing a label and an input field. Important: The width of the input field is defined by the nesting div container using the responsive grid classes col-sm-9 col md-10. With the classes col-sm-3 col-md-2 for the label, a complete bootstrap row of 12 is filled.

<div class="form-group row">
  <label for="title" class="form-label col-sm-3 col-md-2">Title</label>
  <div class="col-sm-9 col-md-10">
    <input id="title" class="form-control" type="text" name="title" value="<dtml-if title>&dtml-title;</dtml-if>" />

The following buttons are constructed as div element with the classname zmi-controls; the buttons use systematically the bootstrap class pair btn btn-primary.

<div class="zmi-controls">
  <input class="btn btn-primary" type="submit" name="submit" value="Save" />

The following example code shows a whole restructured DTML template rendering the Zope 4 ZMI:

Example: updated DTML template (from: ../Zope/src/OFS/dtml/documentEdit.dtml)

 1<dtml-var manage_page_header>
 3<dtml-var manage_tabs>
 5<main class="container-fluid">
 7  <p class="form-help">
 8      You may edit the source for this document using the form below. You
 9      may also upload the source for this document from a local file. Click
10      the <em>browse</em> button to select a local file to upload.
11  </p>
13  <form action="manage_edit" method="post" class="zmi-dtml zmi-edit">
15    <dtml-with keyword_args mapping>
16      <div class="form-group row">
17        <label for="title" class="form-label col-sm-3 col-md-2">Title</label>
18        <div class="col-sm-9 col-md-10">
19          <input id="title" class="form-control" type="text" name="title"
20                 value="<dtml-if title>&dtml-title;</dtml-if>" />
21        </div>
22      </div>
23      <div class="form-group">
24        <textarea id="content" data-contenttype="html"
25                  class="form-control zmi-code col-sm-12"
26                  name="data:text" wrap="off"
27                  rows="20"><dtml-var __str__></textarea>
28      </div>
29    </dtml-with>
31    <div class="zmi-controls">
32      <dtml-if wl_isLocked>
33        <input class="btn btn-primary disabled" type="submit"
34               name="submit" value="Save Changes" disabled="disabled" />
35        <span class="badge badge-warning"
36              title="This item has been locked by WebDAV">
37          <i class="fa fa-lock"></i>
38        </span>
39      <dtml-else>
40        <input class="btn btn-primary" type="submit" name="submit"
41               value="Save Changes" />
42      </dtml-if>
43    </div>
45  </form>
47  <dtml-unless wl_isLocked>
48    <form action="manage_upload" method="post"
49          enctype="multipart/form-data" class="zmi-upload mt-4">
50      <div class="input-group" title="Select Local File for Uploading">
51        <div class="custom-file">
52          <input type="file" name="file" class="custom-file-input"
53                 id="file-data" value=""
54                 onchange="$('.custom-file label span').html($(this).val().replace(/^.*(\\|\/|\:)/, ''));" />
55          <label class="custom-file-label" for="file-data">
56            <span>Choose file</span>
57          </label>
58        </div>
59        <div class="input-group-append">
60            <input class="btn btn-outline-secondary" type="submit"
61                   value="Upload File" />
62        </div>
63      </div>
64    </form>
65  </dtml-unless>
69<dtml-var manage_page_footer>

More details

Textarea: A text area element for editing template code or script code uses the JS library ace for syntax high-lighting and line numbering. Textarea elements which are declared by the CSS class zmi-code are transformed into an ace editor field. Moreover this element has an attribute data-contenttype which is needed by ace-editor to determine the fitting syntax highlighting. ZPT-Example see: ../Zope/src/Products/PageTemplates/www/ptEdit.zpt

File upload element: The file upload element has its own form container (classfied as zmi-upload). All subsequent elements are nested as input-group containing a div classified as custom-file nesting the actual input element. An inline JS fired on the onchange event beautifies the file name shown after selecting it. ZPT-Example see: ../Zope/src/Products/PageTemplates/www/ptEdit.zpt

Hints and Warnings: Some input fields show additional information; these are added as element <small> directly following the referred input field. (Both elements are nested by the width defining div container). Possible text colors are declared by typical bootstrap class names like text-warning.

Icons: Zope 4 object classes which are shown in the ZMI have declared a class variable zmi_icon; this string corresponds to an appropriate font icon-CSS class supplied by the Fontawsome web font (https://fontawesome.com/icons)-

Tables: Bootstrap requires an explicit CSS class table for any table; especially long item lists should get an additional CSS class table-sm and maybe another class table-striped for a better readability. Finally it is recommended to add a specific id attribute like zmi-db_info. The general table structure is compliant to bootstrap standard table (https://getbootstrap.com/docs/4.1/content/tables/).

ZMI-classes: All basic styling of the zmi-elements is defined in the CSS file, see: ../Zope/src/zmi/styles/resources/zmi_base.css

Implicit handling of old Zope 2 ZMI templates: Old templates which do not contain the <main> element are automatically post-processed by a JavaScript function in the browser. The DOM is minimally modified, so that old forms will fit somehow into the Zope 4 layout. In the page footer a hint about this automatically customizing is shown.