[feature] New custom function to get the colors from categories used

DataPlotly/core/plot_expressions.py

@@ -0,0 +1,54 @@
+# -*- coding: utf-8 -*-
+"""
+/***************************************************************************
+ DataPlotly
+                                 A QGIS plugin
+ D3 Plots for QGIS
+                              -------------------
+        begin                : 2022-06-08
+        git sha              : $Format:%H$
+        copyright            : (C) 2020 by matteo ghetta
+        email                : matteo.ghetta@faunalia.it
+ ***************************************************************************/
+
+/***************************************************************************
+ *                                                                         *
+ *   This program is free software; you can redistribute it and/or modify  *
+ *   it under the terms of the GNU General Public License as published by  *
+ *   the Free Software Foundation; either version 2 of the License, or     *
+ *   (at your option) any later version.                                   *
+ *                                                                         *
+ ***************************************************************************/
+"""
+
+from qgis.utils import qgsfunction
+from qgis.core import QgsRenderContext
+
+
+@qgsfunction(args='auto', group='DataPlotly')
+def get_symbol_colors(feature, parent, context):
+    """
+        Retrieve the color of each category as html code. You can use this function
+        to set the plot items (pie slices, bars, points, etc) to the same color
+        of the feature visible in the map.
+        <h4>Syntax</h4>
+        <p>
+            get_symbol_colors() -> '#da1ddd'
+        </p>
+    """
+
+    layer = context.variable('layer')
+    renderer_context = QgsRenderContext()
+    renderer = layer.renderer()
+    renderer.startRender(renderer_context, layer.fields())
+
+    symbols = renderer.originalSymbolsForFeature(feature, renderer_context)
+
+    if symbols:
+        color = symbols[0].color().name()
+    else:
+        color = '#000000'
+
+    renderer.stopRender(renderer_context)
+
+    return color

DataPlotly/data_plotly.py

@@ -25,7 +25,7 @@
 from qgis.PyQt.QtCore import QSettings, QTranslator, QCoreApplication, Qt, QUrl
 from qgis.PyQt.QtGui import QDesktopServices
 from qgis.PyQt.QtWidgets import QAction
-from qgis.core import Qgis, QgsApplication
+from qgis.core import Qgis, QgsApplication, QgsExpression
 from qgis.gui import QgsGui
 
 # Import the code for the dialog
@@ -39,6 +39,9 @@
 from DataPlotly.layouts.plot_layout_item import PlotLayoutItemMetadata
 from DataPlotly.gui.layout_item_gui import PlotLayoutItemGuiMetadata
 
+# import custom expressions
+from .core.plot_expressions import get_symbol_colors
+
 
 class DataPlotly:  # pylint: disable=too-many-instance-attributes
     """QGIS Plugin Implementation."""
@@ -132,6 +135,9 @@ def initGui(self):
             self.iface.pluginHelpMenu().addAction(self.help_action)
             self.help_action.triggered.connect(self.open_help)
 
+        # register the function
+        QgsExpression.registerFunction(get_symbol_colors)
+
     def initProcessing(self):
         """Create the Processing provider"""
         QgsApplication.processingRegistry().addProvider(self.provider)
@@ -151,6 +157,9 @@ def unload(self):
         # Remove processing provider
         QgsApplication.processingRegistry().removeProvider(self.provider)
 
+        # unregister the function
+        QgsExpression.unregisterFunction('get_symbol_colors')
+
     @staticmethod
     def open_help():
         """ Open the online help. """