"""Produce SVG versions of active plots for display by the rich Qt frontend.
"""
#-----------------------------------------------------------------------------
# Imports
#-----------------------------------------------------------------------------

# Standard library imports
from cStringIO import StringIO

# System library imports.
from matplotlib.backends.backend_svg import new_figure_manager
from matplotlib._pylab_helpers import Gcf

# Local imports.
from backend_payload import add_plot_payload

#-----------------------------------------------------------------------------
# Functions
#-----------------------------------------------------------------------------

def show():
    """ Deliver a SVG payload.
    """
    for figure_manager in Gcf.get_all_fig_managers():
        # Make the background transparent.
        # figure_manager.canvas.figure.patch.set_alpha(0.0)
        # Set the background to white instead so it looks good on black.
        figure_manager.canvas.figure.set_facecolor('white')
        figure_manager.canvas.figure.set_edgecolor('white')
        data = svg_from_canvas(figure_manager.canvas)
        add_plot_payload('svg', data)


def svg_from_canvas(canvas):
    """ Return a string containing the SVG representation of a FigureCanvasSvg.
    """
    string_io = StringIO()
    canvas.print_svg(string_io)
    return string_io.getvalue()