def create_tableau(factory, location):
""" Create a single tableau for a given location using a given factory.
This function does the actual work of generating an individual tableau
based upon the factory definition. It can be called directly to
generate a desired tableau, or it can be called indirectly by the
daemon (using the private 'create_tableau' API call) to generate
tableaux en masse.
Upon completion, we return None if the tableau-generation attempt was
successful. Otherwise, we return a suitable error message explaining
why the tableau could not be generated.
"""
# Get the location's outline.
try:
outline = Outline.objects.get(location=location)
except Outline.DoesNotExist:
# We can't create a tableau for a location without an outline ->
# tell the user the bad news.
return "Location has no outline."
# Delete the existing tableau with this name, if any.
Tableau.objects.filter(location=location,
name=factory.tableau_name).delete()
# Create the new Tableau for this location.
tableau = Tableau()
tableau.location = location
tableau.name = factory.tableau_name
tableau.meta_data = factory.tableau_meta_data
tableau.bounds_render = factory.tableau_bounds_render
tableau.save()
# Create a single view for the tableau, covering the location's entire
# extent.
min_long,min_lat,max_long,max_lat = outline.outline.extent
# Add a margin around the edges so that the location is easier to see.
width = abs(max_long - min_long)
height = abs(max_lat - min_lat)
buffer = 0.02 * (width + height) / 2
min_long = min_long - buffer
max_long = max_long + buffer
min_lat = min_lat - buffer
max_lat = max_lat + buffer
# Ensure the calculated view bounds are allowable.
if min_lat < MIN_ALLOWED_LATITUDE:
min_lat = MIN_ALLOWED_LATITUDE
elif min_lat > MAX_ALLOWED_LATITUDE:
min_lat = MAX_ALLOWED_LATITUDE
if max_lat < MIN_ALLOWED_LATITUDE:
max_lat = MIN_ALLOWED_LATITUDE
elif max_lat > MAX_ALLOWED_LATITUDE:
max_lat = MAX_ALLOWED_LATITUDE
if min_long < MIN_ALLOWED_LONGITUDE:
min_long = MIN_ALLOWED_LONGITUDE
elif min_long > MAX_ALLOWED_LONGITUDE:
min_long = MAX_ALLOWED_LONGITUDE
if max_long < MIN_ALLOWED_LONGITUDE:
max_long = MIN_ALLOWED_LONGITUDE
elif max_long > MAX_ALLOWED_LONGITUDE:
max_long = MAX_ALLOWED_LONGITUDE
# Create the view.
view = TableauView()
view.tableau = tableau
view.ordinal_rank = 1
view.name = location.display_name
view.min_lat = "%0.4f" % min_lat
view.max_lat = "%0.4f" % max_lat
view.min_long = "%0.4f" % min_long
view.max_long = "%0.4f" % max_long
view.meta_data = factory.view_meta_data
view.bounds_render = factory.view_bounds_render
view.save()
# Add the factory's filter(s) to the tableau's view.
for factory_filter in factory.tableaufactoryviewfilter_set.all():
filter = TableauViewFilter()
filter.tableauView = view
filter.type = factory_filter.filter_type
filter.value = factory_filter.filter_value
filter.meta_data = factory_filter.filter_meta_data
filter.draw_bubbles = factory_filter.filter_draw_bubbles
filter.polygon_render = factory_filter.filter_polygon_render
filter.bubble_render = factory_filter.filter_bubble_render
filter.save()
# Calculate the aspect ratio for the tableau's view.
proj = GlobalMercator()
min_x,min_y = proj.LatLonToMeters(min_lat, min_long)
max_x,max_y = proj.LatLonToMeters(max_lat, max_long)
viewWidth = max_x - min_x
viewHeight = max_y - min_y
if viewWidth == 0: viewWidth = 1.0
if viewHeight == 0: viewHeight = 1.0
aspectRatio = viewWidth / viewHeight
# Create a single layout for the tableau. The size of the layout is
# based on the view's aspect ratio.
layout_width = LAYOUT_MAX_WIDTH
layout_height = layout_width / aspectRatio
if layout_height > LAYOUT_MAX_HEIGHT:
layout_height = LAYOUT_MAX_HEIGHT
layout_width = layout_height * aspectRatio
layout = TableauLayout()
layout.tableau = tableau
layout.width = layout_width
layout.height = layout_height
layout.save()
# Create a single TableauLayoutViewPosition record, positioning the view
# within the layout.
position = TableauLayoutViewPosition()
position.tableauLayout = layout
position.tableauView = view
position.min_x = 0
position.min_y = 0
position.max_x = layout_width
position.max_y = layout_height
position.save()
# Finally, tell the caller that the tableau was successfully generated.
return None
