Add a bit of tolerance to graduated symbol range resolving

If a value doesn't fall exactly within a range, then try to see if it falls just outside of any ranges (within double precision tolerance), to correctly handle double precision values coming from different sources. Fixes #27420 (cherry picked from commit e9d51e5)
qgis · Nov 14, 2019 · ac66b07 · ac66b07
1 parent 4033bd4
commit ac66b07
Show file tree

Hide file tree

Showing 2 changed files with 18 additions and 0 deletions.
diff --git a/src/core/symbology/qgsgraduatedsymbolrenderer.cpp b/src/core/symbology/qgsgraduatedsymbolrenderer.cpp
@@ -84,6 +84,20 @@ const QgsRendererRange *QgsGraduatedSymbolRenderer::rangeForValue( double value
         return nullptr;
     }
   }
+
+  // second chance -- use a bit of double tolerance to avoid floating point equality fuzziness
+  // if a value falls just outside of a range, but within acceptable double precision tolerance
+  // then we accept it anyway
+  for ( const QgsRendererRange &range : mRanges )
+  {
+    if ( qgsDoubleNear( range.lowerValue(), value ) || qgsDoubleNear( range.upperValue(), value ) )
+    {
+      if ( range.renderState() || mCounting )
+        return &range;
+      else
+        return nullptr;
+    }
+  }
   // the value is out of the range: return NULL instead of symbol
   return nullptr;
 }

diff --git a/tests/src/core/testqgsgraduatedsymbolrenderer.cpp b/tests/src/core/testqgsgraduatedsymbolrenderer.cpp
@@ -309,6 +309,10 @@ void TestQgsGraduatedSymbolRenderer::testMatchingRangeForValue()
   QCOMPARE( renderer.legendKeyForValue( 3.25 ), QStringLiteral( "1" ) );
   QCOMPARE( renderer.legendKeyForValue( 3.7 ), QStringLiteral( "3" ) );
   QVERIFY( renderer.legendKeyForValue( 3.5 ).isEmpty() );
+
+  // test values which fall just outside ranges, e.g. due to double precision (refs https://github.com/qgis/QGIS/issues/27420)
+  QCOMPARE( renderer.rangeForValue( 1.1 - std::numeric_limits<double>::epsilon() * 2 )->label(), QStringLiteral( "r1" ) );
+  QCOMPARE( renderer.rangeForValue( 3.7 + std::numeric_limits<double>::epsilon() * 2 )->label(), QStringLiteral( "r4" ) );
 }
 
 QGSTEST_MAIN( TestQgsGraduatedSymbolRenderer )