=============
Image Widget
=============

The image widget allows you to submit a form to the server by clicking on an
image. The "image" type of the "INPUT" element is described here:

http://www.w3.org/TR/1999/REC-html401-19991224/interact/forms.html#edef-INPUT

As for all widgets, the image widget must provide the new ``IWidget``
interface:

  >>> from zope.interface.verify import verifyClass
  >>> from z3c.form import interfaces
  >>> from z3c.form.browser import image

  >>> verifyClass(interfaces.IWidget, image.ImageWidget)
  True

The widget can be instantiated only using the request:

  >>> from z3c.form.testing import TestRequest
  >>> request = TestRequest()

  >>> widget = image.ImageWidget(request)

Before rendering the widget, one has to set the name and id of the widget:

  >>> widget.id = 'widget.id'
  >>> widget.name = 'widget.name'

We also need to register the template for the widget:

  >>> import zope.component
  >>> from zope.pagetemplate.interfaces import IPageTemplate
  >>> from z3c.form.testing import getPath
  >>> from z3c.form.widget import WidgetTemplateFactory

  >>> zope.component.provideAdapter(
  ...     WidgetTemplateFactory(getPath('image_input.pt'), 'text/html'),
  ...     (None, None, None, None, interfaces.IImageWidget),
  ...     IPageTemplate, name=interfaces.INPUT_MODE)

If we render the widget we get a simple input element:

  >>> print(widget.render())
  <input type="image" id="widget.id" name="widget.name"
         class="image-widget" />

Setting an image source for the widget effectively changes the "src" attribute:

  >>> widget.src = u'widget.png'
  >>> print(widget.render())
  <input type="image" id="widget.id" name="widget.name"
         class="image-widget" src="widget.png" />


Let's now make sure that we can extract user entered data from a widget:

  >>> widget.request = TestRequest(
  ...     form={'widget.name.x': '10',
  ...           'widget.name.y': '20',
  ...           'widget.name': 'value'})
  >>> widget.update()
  >>> sorted(widget.extract().items())
  [('value', 'value'), ('x', 10), ('y', 20)]


If nothing is found in the request, the default is returned:

  >>> widget.request = TestRequest()
  >>> widget.update()
  >>> widget.extract()
  <NO_VALUE>