Add viz default helpers

[Jesus89]

Closes #1430

PoC implementation of default values and default helpers.

# Layer with default style

Layer(
    'population'
)


# Layer with custom style: legend and hover enabled by default

Layer(
    'population',
    color_bins_style('pop_max')
)


# Layer with default UI components enabled
# It uses "pop_max" as the default title for Legend, Widget and Popup

Layer(
    'population',
    color_bins_style('pop_max'),
    default_legend=True,
    default_widget=True,
    default_popup_hover=True,
    default_popup_click=True
)


# Layer with default UI components enabled with custom title
# It uses "Max population" as the default title for Legend, Widget and Popup

Layer(
    'population',
    color_bins_style('pop_max'),
    default_legend=True,
    default_widget=True,
    default_popup_hover=True,
    default_popup_click=True,
    title='Max population'
)


# Layer with default UI components enabled with custom content

Layer(
    'population',
    color_bins_style('pop_max'),
    legends=default_legend('Legend title', 'Legend description', 'Legend footer'),
    widgets=default_widget('Widget title', 'Widget description', 'Widget footer'),
    popup_hover=default_popup_element('Popup title (Hover)'),
    popup_click=default_popup_element('Popup title (Click)')
)


# Layer with default + new UI components

Layer(
    'population',
    color_bins_style('pop_max'),
    legends=[default_legend('Legend title', 'Legend description', 'Legend footer'), basic_legend('Title', 'description', 'footer')],
    widgets=[default_widget('Widget title', 'Widget description', 'Widget footer') histogram_widget('cartodb_id', 'CARTODB ID')],
    popup_hover=[default_popup_element('Popup title (Hover)'), popup_element('cartodb_id', 'CARTODB ID')]
    popup_click=[default_popup_element('Popup title (Click)'), popup_element('cartodb_id', 'CARTODB ID')]
)

[makella]

I'm still trying to understand how the components are loaded as part of a style while at the same time not part of the style but that's my own thing to sort through!

Here are some comments/questions after taking a look through:

• Shouldn't we also have a default_style? I guess that is the basic_style but to keep consistent, should that be renamed?

• How do I easily change the title of the hover that is available with the style? Finding this confusing and unless I also define the attribute (basically recreating the hover popup from scratch ). default_popup=(title='my title') for instance seemed the logical way with the other patterns, but this isn't working for me. This is what worked:

Layer(
    'eng_wales_pop', 
    color_bins_style('pop_sq_km'),
    default_legend(title='Legend'),
    default_widget(title='Distribution'),
    popup_element('pop_sq_km', title='Value')
)

There seem to be a couple of different ways to do this, so maybe I am missing something! I also don't really understand why things like widgets=True works even though something like default_widget=True doesn't work but default_widget is what I use to customize the widget I get when I use widgets=True. I get that behind the scenes it is widgets=default_widget(...) but as you can see, I'm still getting my head around it!

• Related, in help(Layer) it says that you only get a hover popup with a style but if I set both hover_popup and/or click_popup to True, I get both.

• Regarding the default titles
  Suggestion here is to give more meaningful titles to each component by default, not just the widget:

  • set legend title to "Legend"
  • set hover title to "Value"
  • set widget title to "Categories" / "Distribution"

Example category:

Example numeric:

I'm gonna keep working with this new stuff to understand it better..
thanks!

[Jesus89]

Hi 👋, I have updated the ticket description with the changes from the last meeting.

[elenatorro]

Note: update examples cc @Jesus89

[Jesus89]

I have added an example in the PR to test this: examples/_debug/viz-flow.

[elenatorro]

As we've talked, after this is ready for merge let's add it and review doc related stuff in this issue #1419

[elenatorro]

LGTM 🚀