Add isValid() method for QgsScaleBarRenderer::RendererContext

python/PyQt6/core/auto_generated/scalebar/qgsscalebarrenderer.sip.in

@@ -55,6 +55,13 @@ custom labeling.
 
       Flags flags;
 
+      bool isValid() const;
+%Docstring
+Returns ``True`` if the context has valid settings.
+
+.. versionadded:: 3.40
+%End
+
     };
 
     QgsScaleBarRenderer();

python/core/auto_generated/scalebar/qgsscalebarrenderer.sip.in

@@ -55,6 +55,13 @@ custom labeling.
 
       Flags flags;
 
+      bool isValid() const;
+%Docstring
+Returns ``True`` if the context has valid settings.
+
+.. versionadded:: 3.40
+%End
+
     };
 
     QgsScaleBarRenderer();

src/core/scalebar/qgsscalebarrenderer.cpp

@@ -418,3 +418,8 @@ QList<double> QgsScaleBarRenderer::segmentWidths( const ScaleBarContext &scaleCo
 
   return widths;
 }
+
+bool QgsScaleBarRenderer::ScaleBarContext::isValid() const
+{
+  return !std::isnan( segmentWidth );
+}

src/core/scalebar/qgsscalebarrenderer.h

@@ -66,7 +66,7 @@ class CORE_EXPORT QgsScaleBarRenderer
      * Contains parameters regarding scalebar calculations.
      * \note The need to attribute the parameters vary depending on the targeted scalebar.
      */
-    struct ScaleBarContext
+    struct CORE_EXPORT ScaleBarContext
     {
 
       /**
@@ -88,6 +88,13 @@ class CORE_EXPORT QgsScaleBarRenderer
       //! Scalebar renderer flags
       Flags flags;
 
+      /**
+       * Returns TRUE if the context has valid settings.
+       *
+       * \since QGIS 3.40
+       */
+      bool isValid() const;
+
     };
 
     QgsScaleBarRenderer() = default;

tests/src/python/CMakeLists.txt

@@ -302,6 +302,7 @@ ADD_PYTHON_TEST(PyQgsRenderedItemResults test_qgsrendereditemresults.py)
 ADD_PYTHON_TEST(PyQgsRenderer test_qgsrenderer.py)
 ADD_PYTHON_TEST(PyQgsReport test_qgsreport.py)
 ADD_PYTHON_TEST(PyQgsScaleBarRendererRegistry test_qgsscalebarrendererregistry.py)
+ADD_PYTHON_TEST(PyQgsScaleBarRenderers test_qgsscalebarrenderers.py)
 ADD_PYTHON_TEST(PyQgsScaleCalculator test_qgsscalecalculator.py)
 ADD_PYTHON_TEST(PyQgsSingleBandColorDataRenderer test_qgssinglebandcolordatarenderer.py)
 ADD_PYTHON_TEST(PyQgsSingleBandGrayRenderer test_qgssinglebandgrayrenderer.py)

tests/src/python/test_qgsscalebarrenderers.py

@@ -0,0 +1,29 @@
+"""QGIS Unit tests for scale bar renderers
+
+.. note:: 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.
+"""
+
+import math
+
+from qgis.core import QgsScaleBarRenderer
+import unittest
+from qgis.testing import start_app, QgisTestCase
+
+start_app()
+
+
+class TestQgsScaleBarRenderers(QgisTestCase):
+
+    def test_context(self):
+        context = QgsScaleBarRenderer.ScaleBarContext()
+        context.segmentWidth = 5
+        self.assertTrue(context.isValid())
+        context.segmentWidth = math.nan
+        self.assertFalse(context.isValid())
+
+
+if __name__ == '__main__':
+    unittest.main()