def run(self):
"""Makes a few sanity checks and prepares the worker thread."""
# create the dialog (after translation) and keep reference
self.dialog = CartogramDialog()
# make sure we have at least one vector layer to work on
count = self.count_vector_layers()
if count == 0:
message = self.tr('You need at least one vector layer to create a '
'cartogram.')
self.iface.messageBar().pushMessage('Error', message,
level=QgsMessageBar.CRITICAL, duration=5)
return False
# we are only interested in polygon layers and numeric fields
self.dialog.sourceLayerCombo.setFilters(
QgsMapLayerProxyModel.PolygonLayer)
self.dialog.sourceFieldCombo.setFilters(QgsFieldProxyModel.Numeric)
# select the first layer in the list and notify the field combobox
self.dialog.sourceLayerCombo.setCurrentIndex(0)
currentLayer = self.dialog.sourceLayerCombo.currentLayer()
self.dialog.sourceLayerCombo.layerChanged.emit(currentLayer)
# connect some odds and ends
self.dialog.buttonBox.accepted.connect(self.validate)
# show the dialog
self.dialog.show()
result = self.dialog.exec_()
if result == QDialog.Rejected:
return False
input_layer_name = self.dialog.sourceLayerCombo.currentText()
input_layer = self.get_vector_layer_by_name(input_layer_name)
input_field = self.dialog.sourceFieldCombo.currentText()
iterations = self.dialog.iterationsSpinBox.value()
memory_layer = self.create_memory_layer(input_layer)
memory_layer_data_provider = memory_layer.dataProvider()
self.worker_start(memory_layer, input_field, iterations)
class Cartogram:
"""QGIS Plugin Implementation."""
def __init__(self, iface):
"""Constructor.
:param iface: An interface instance that will be passed to this class
which provides the hook by which you can manipulate the QGIS
application at run time.
:type iface: QgsInterface
"""
# save reference to the QGIS interface
self.iface = iface
# initialize plugin directory
self.plugin_dir = os.path.dirname(__file__)
# initialize locale
locale = QSettings().value('locale/userLocale')[0:2]
locale_path = os.path.join(
self.plugin_dir,
'i18n',
'{}.qm'.format(locale))
if os.path.exists(locale_path):
self.translator = QTranslator()
self.translator.load(locale_path)
if qVersion() > '4.3.3':
QCoreApplication.installTranslator(self.translator)
# declare instance attributes
self.action = None
self.menu = self.tr('&Cartogram')
def initGui(self):
"""Create the menu entries and toolbar icons inside the QGIS GUI."""
# create action to display the settings dialog
self.run_action = QAction(
QIcon(':/plugins/cartogram/assets/icon.png'),
self.tr('Create cartogram...'),
self.iface.mainWindow())
self.demo_action = QAction(
self.tr('Add demo layer'),
self.iface.mainWindow())
# connect the actions to their respective methods
self.run_action.triggered.connect(self.run)
self.demo_action.triggered.connect(self.demo)
# add toolbar button and menu items
self.iface.addToolBarIcon(self.run_action)
self.iface.addPluginToVectorMenu(self.menu, self.run_action)
self.iface.addPluginToVectorMenu(self.menu, self.demo_action)
def unload(self):
"""Removes the plugin menu item and icon from the QGIS GUI."""
self.iface.removePluginVectorMenu('&Cartogram', self.run_action)
self.iface.removePluginVectorMenu('&Cartogram', self.demo_action)
self.iface.removeToolBarIcon(self.run_action)
def run(self):
"""Makes a few sanity checks and prepares the worker thread."""
# create the dialog (after translation) and keep reference
self.dialog = CartogramDialog()
# make sure we have at least one vector layer to work on
count = self.count_vector_layers()
if count == 0:
message = self.tr('You need at least one vector layer to create a '
'cartogram.')
self.iface.messageBar().pushMessage('Error', message,
level=QgsMessageBar.CRITICAL, duration=5)
return False
# we are only interested in polygon layers and numeric fields
self.dialog.sourceLayerCombo.setFilters(
QgsMapLayerProxyModel.PolygonLayer)
self.dialog.sourceFieldCombo.setFilters(QgsFieldProxyModel.Numeric)
# select the first layer in the list and notify the field combobox
self.dialog.sourceLayerCombo.setCurrentIndex(0)
currentLayer = self.dialog.sourceLayerCombo.currentLayer()
self.dialog.sourceLayerCombo.layerChanged.emit(currentLayer)
# connect some odds and ends
self.dialog.buttonBox.accepted.connect(self.validate)
# show the dialog
self.dialog.show()
result = self.dialog.exec_()
if result == QDialog.Rejected:
return False
input_layer_name = self.dialog.sourceLayerCombo.currentText()
input_layer = self.get_vector_layer_by_name(input_layer_name)
input_field = self.dialog.sourceFieldCombo.currentText()
iterations = self.dialog.iterationsSpinBox.value()
memory_layer = self.create_memory_layer(input_layer)
memory_layer_data_provider = memory_layer.dataProvider()
self.worker_start(memory_layer, input_field, iterations)
def demo(self):
path = self.plugin_dir + '/demo/demo.shp'
layer = QgsVectorLayer(path, 'Cartogram demo layer', 'ogr')
QgsMapLayerRegistry.instance().addMapLayer(layer)
def worker_start(self, layer, field_name, iterations):
"""Start a worker instance on a background thread."""
worker = CartogramWorker(layer, field_name, iterations)
message_bar = self.iface.messageBar().createMessage('')
label = QLabel('Creating cartogram...')
label.setAlignment(Qt.AlignLeft | Qt.AlignVCenter)
progress_bar = QProgressBar()
progress_bar.setAlignment(Qt.AlignLeft | Qt.AlignVCenter)
progress_bar.setMaximum(iterations * layer.featureCount())
cancel_button = QPushButton()
cancel_button.setText(self.tr('Cancel'))
cancel_button.clicked.connect(worker.kill)
message_bar.layout().addWidget(label)
message_bar.layout().addWidget(progress_bar)
message_bar.layout().addWidget(cancel_button)
self.iface.messageBar().pushWidget(message_bar,
self.iface.messageBar().INFO)
self.message_bar = message_bar
# start the worker in a new thread
thread = QThread()
worker.moveToThread(thread)
# connect some odds and ends
worker.finished.connect(self.worker_finished)
worker.error.connect(self.worker_error)
worker.progress.connect(progress_bar.setValue)
thread.started.connect(worker.run)
thread.start()
self.thread = thread
self.worker = worker
def worker_finished(self, layer):
"""Clean up after the worker and the thread."""
self.worker.deleteLater()
self.thread.quit()
self.thread.wait()
self.thread.deleteLater()
self.iface.messageBar().popWidget(self.message_bar)
if layer is not None:
QgsMapLayerRegistry.instance().addMapLayer(layer)
else:
message = self.tr('Cartogram creation cancelled by user.')
self.iface.messageBar().pushMessage(message,
level=QgsMessageBar.INFO, duration=3)
def worker_error(self, e, exception_string):
message = 'Worker thread exception:\n'.format(exception_string)
QgsMessageLog.logMessage(message, level=QgsMessageLog.CRITICAL)
def validate(self):
"""Make sure that all fields have valid values."""
message = ''
if not self.dialog.sourceLayerCombo.currentText():
message += self.tr('Please select an input layer.')
if not self.dialog.sourceFieldCombo.currentText():
message += self.tr('Please select an area field.')
if message:
QMessageBox.warning(self.dialog, 'Cartogram', message)
else:
self.dialog.accept()
# noinspection PyMethodMayBeStatic
def tr(self, message):
"""Get the translation for a string using Qt translation API."""
# noinspection PyTypeChecker,PyArgumentList,PyCallByClass
return QCoreApplication.translate('Cartogram', message)
def get_vector_layer_by_name(self, layer_name):
"""Retrieve a layer from the registry by name."""
layerMap = QgsMapLayerRegistry.instance().mapLayers()
for name, layer in layerMap.iteritems():
if layer.type() == QgsMapLayer.VectorLayer \
and layer.name() == layer_name:
if layer.isValid():
return layer
else:
return None
def count_vector_layers(self):
"""Count the number of vector layers on the canvas."""
layermap = QgsMapLayerRegistry.instance().mapLayers()
count = 0
for name, layer in layermap.iteritems():
if layer.type() == QgsMapLayer.VectorLayer:
if layer.geometryType() == QGis.Polygon:
count += 1
return count
def create_memory_layer(self, layer):
"""Create an in-memory copy of an existing vector layer."""
data_provider = layer.dataProvider()
# create the layer path defining geometry type and reference system
geometry_type = QGis.vectorGeometryType(layer.geometryType())
crs_id = layer.crs().authid()
path = geometry_type + '?crs=' + crs_id + '&index=yes'
# create the memory layer and get a reference to the data provider
memory_layer = QgsVectorLayer(path, 'Cartogram', 'memory')
memory_layer_data_provider = memory_layer.dataProvider()
# copy all attributes from the source layer to the memory layer
memory_layer.startEditing()
memory_layer_data_provider.addAttributes(
data_provider.fields().toList())
memory_layer.commitChanges()
# copy all features from the source layer to the memory layer
for feature in data_provider.getFeatures():
memory_layer_data_provider.addFeatures([feature])
return memory_layer
