Layout example

A Widget can use a predefined (but configurable) Layout to change what it looks like. Different Layouts could be used with the same Widget on different apps or different contexts.

Some special widgets are also provided to help position elements on a page. The example presented here shows some layout examples.

We provide some styling for a basic look which you can use while programming while web designers can create your perfect look in parallel for each applicable Widget.

The source code given below results in the following visual layout:

Screenshot of a page with header, footer, two columns and a few other layout features demonstrated.

In this example, the page used is not specified per View, but a single page is used for the entire UserInterface. Each View (there’s only one here) just specifies some contents for the named Slots provided by that page. (See Make light work of similar-looking pages for an explanation.)

PageColumnLayout is used in this example to change the HTMLPage of the application to have a header and footer with a content area inbetween the two, that is itself split into columns. Each column created by the PageColumnLayout contains a Slot with the same name as the column.

The row variable is a Panel split into columns using a simpler ColumnLayout.

Widgets like the LabelledBlockInput can be used to do the internal layout of elements of a form. A LabelledBlockInput wraps around any simple input and provides it with a label. It also positions all the relevant constituent elements neatly — including possible validation error messages.

from __future__ import print_function, unicode_literals, absolute_import, division

from reahl.web.fw import UserInterface
from reahl.web.ui import HTML5Page, Form, TextInput, LabelledBlockInput, P, Panel
from reahl.web.pure import ColumnLayout, PageColumnLayout, UnitSize
from reahl.component.modelinterface import exposed, Field, EmailField

def lots_of(message):
    return message * 5

class LayoutUI(UserInterface):
    def assemble(self):
        layout = PageColumnLayout(('secondary', UnitSize(default='1/3')), 
                                  ('main', UnitSize(default='2/3')))
        self.define_page(HTML5Page, style='basic').use_layout(layout)  

        home = self.define_view('/', title='Layout demo')
        home.set_slot('main', CommentForm.factory())

        secondary_text = lots_of('The secondary column sits on '
                                 'the left side of the main column, '
                                 'spanning 1/3 of the body. ')
        home.set_slot('secondary', P.factory(text=secondary_text))

        header_text = lots_of('This text is located in the header,'
                              'which is added by the PageColumnLayout. ')
        home.set_slot('header', P.factory(text=header_text))

        footer_text = lots_of('The footer spans the bottom of all the '
                              'columns on a PageColumnLayout ')
        home.set_slot('footer', P.factory(text=footer_text))

class Comment(object):
    def fields(self, fields):
        fields.email_address = EmailField(label='Email address', required=True)
        fields.text = Field(label='Comment text')

class CommentForm(Form):
    def __init__(self, view):
        super(CommentForm, self).__init__(view, 'myform')

        comment = Comment()
        email_input = TextInput(self, comment.fields.email_address)

        text_input = TextInput(self, comment.fields.text)

        layout = ColumnLayout(('left', UnitSize(default='1/2')), 
                              ('right', UnitSize(default='1/2')))
        row = self.add_child(Panel(view).use_layout(layout))

        left_p = P(view, text='This is in the left column of the row')

        right_p = P(view, text='This is in the right column of the row')

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