Widgets Reference
=================

Widgets are report elements to show text values on report canvas.

All widget classes can be initialized with their attributes as class arguments.

Widget
------

.. currentmodule:: geraldo.widgets
.. class:: Widget

Path: **geraldo.widgets.Widget**

Base class for reports widgets, you should use it only to inherit and make your
own widgets, otherwise you shouldn't use it directly.

**Attributes**

- **name** - Default: None
- **height** - Default: 0.5*cm
- **width** - Default: 5*cm
- **left** - Default: 0
- **top** - Default: 0
- **visible** - Default: True

    Set to **False** if you want to make it not visible.

- **borders** - Default: {'top': None, 'right': None, 'bottom': None, 'left': None, 'all': None}

    Borders values can be of three types:

    - Boolean (True/False) - just set if there is a border or not
    - Integer - set there is a border and what is its stroke width. **New on 0.4.**
    - Graphic (instance of Rect, Line, RoundRect, etc.) - set a complex graphic to put along the border

- **style** - Default: {}

    This is a dictionary that uses the powerful ReportLab **ParagraphStyle**
    class to set style settings for this widget.

    Default keys are:

    - **fontName** - Default: 'Times-Roman',
    - **fontSize** - Default: 10,
    - **leading** - Default: 12,
    - **leftIndent** - Default: 0,
    - **rightIndent** - Default: 0,
    - **firstLineIndent** - Default: 0,
    - **alignment** - Default: TA_LEFT,
    - **spaceBefore** - Default: 0,
    - **spaceAfter** - Default: 0,
    - **bulletFontName** - Default: 'Times-Roman',
    - **bulletFontSize** - Default: 10,
    - **bulletIndent** - Default: 0,
    - **textColor** - Default:  black,
    - **backColor** - Default: None,
    - **wordWrap** - Default: None,
    - **allowWidows** - Default: 1,
    - **allowOrphans** - Default: 0,

- **get_value** - Default: None.

    This is the way you can easily customize the widget output. Be careful
    with this attribute, because each widget has its own set of arguments.

- **truncate_overflow** - Default: False

    When "True", truncate the widget to use only its defined **height** and
    **widget** attributes, with no word wrap. This means that those attributes
    are required.

**Events system**

- **before_print** - Default: None

    Is called by **do_before_print** method, before generate the widget output.
    Expect arguments **widget** and **generator**.

- **after_print** - Default: None

    Is called by **do_after_print** method, after generate the widget output.
    Expect arguments **widget** and **generator**.

**Rendering attributes**

They are read-only attributes you can use at render time.

- **instance** - current object being rendered
- **generator** - generator instance
- **report** - report instance this element is in
- **band** - band this element is in
- **page** - current page

Label
-----

.. currentmodule:: geraldo.widgets
.. class:: Label

Path: **geraldo.Label**

A label is just a simple text.

**Example of use**

    >>> Label(text='Taxes we have paid', left=1*cm, top=0.5*cm, width=10*cm, height=0.5*cm)

**Attributes**

- **height** - Default: 0.5*cm
- **width** - Default: 5*cm
- **left** - Default: 0
- **top** - Default: 0
- **visible** - Default: True
- **style** - Default: {}

**get_value** must have a 'text' argument.

ObjectValue
-----------

.. currentmodule:: geraldo.widgets
.. class:: ObjectValue

Path: **geraldo.ObjectValue**

This shows the value from a method, field or property from objects in the
queryset.
    
You can provide an action to show the object value or an aggregation function on
it.
    
You can also use the 'display_format' attribute to set a friendly string formatting,
with a mask or additional text.

'get_value' lambda must have an 'instance' argument.

**Example of use**

    >>> ObjectValue(attribute_name='name', left=1*cm, top=0.5*cm, width=10*cm, height=0.5*cm)

**Attributes**

- **height** - Default: 0.5*cm
- **width** - Default: 5*cm
- **left** - Default: 0
- **top** - Default: 0
- **visible** - Default: True
- **style** - Default: {}
- **attribute_name** - Required

    You can provide here the object attribute name you want to show in this
    widget. You can provide a field, common attribute, property or just a method,
    since it has no required argument to provide.

    You can use paths of callable or properties instead of attribute name in
    this attribute.

    Examples:

        attribute_name = 'name.upper'
        attribute_name = 'customer.name'
        attribute_name = 'customer.type.name.lower'

- **action** - Default: geraldo.FIELD_ACTION_VALUE

    The action is where you say what Geraldo will do with the value of this
    field. The default action is just to show its value and nothing more.
    
    But if you are using an ObjectValue in a summary or footer band of report,
    group or subreport, you will probably have a need for aggregation functions. This
    is why this attribute exists.
    
    Field actions are all available in the **geraldo** package to import from.
    The choices you can use in **action** attributes are:
    
    - geraldo.FIELD_ACTION_VALUE
    - geraldo.FIELD_ACTION_COUNT
    - geraldo.FIELD_ACTION_AVG
    - geraldo.FIELD_ACTION_MIN
    - geraldo.FIELD_ACTION_MAX
    - geraldo.FIELD_ACTION_SUM
    - geraldo.FIELD_ACTION_DISTINCT_COUNT

- **display_format** - Default: '%s'

    Use simple string formatting on the field value. You could otherwise
    use **get_value** if you want something more powerful.

- **get_text** - Default: None.

    This 'lambda' attribute is seemed to **get_value** because it works after
    value getting. It's important to keep aware there are two moments from get
    a value from instance until to render it on the output generation:
    
    - 1) First the value is getted (and keeps being an unformatted value)
    - 2) After this, the value is formatted (and transformed to unicode string)

- **stores_text_in_cache** - Default: True

    This is a boolean attribute you can set to **False** if you to force the
    text getting to run twice: on renderizing and on generating. If you keep
    it as **True**, it will store the text on the first getting and use the
    stored text on next time(s) it be requested.

SystemField
-----------

.. currentmodule:: geraldo.widgets
.. class:: SystemField

Path: **geraldo.SystemField**

This shows system information, like the report title, current date/time, page
number, page count, etc.
    
'get_value' must have 'expression' and 'fields' arguments.

**Example of use**

    >>> ObjectValue(expression='%(report_title)s', left=1*cm, top=0.5*cm, width=10*cm, height=0.5*cm)

**Attributes**

- **height** - Default: 0.5*cm
- **width** - Default: 5*cm
- **left** - Default: 0
- **top** - Default: 0
- **visible** - Default: True
- **style** - Default: {}
- **expression** - Default: '%(report_title)s'

    This is a simple string you can write with basic macros to show system field
    values.
    
    The available macros are:

    - %(report_title)s
    - %(page_number)s
    - %(first_page_number)s
    - %(last_page_number)s
    - %(page_count)s
    - %(report_author)s
    - %(now:FORMAT)s - in replace of 'FORMAT' you can use date formatting
      standard template filter date formatting. But if you are using your
      own **Report.format_date** method, this will use it.

        Examples:
        
        - '%(now:%Y)' - shows the current year
        - '%(now:%m/%d/%Y)' - shows something like '01/23/2009'

        **Note:** this is changed now. Before this function used Django
        template filter 'date' to format datetime, but once we were
        going to use two standards, this wouldn't be nice. If you want 
        to use Django's template filter, you can override the method
        **Report.format_date(date, expression)** and use it.

