Avoid showing "0.000 deg" in measure dialog for small degree measurem…

…ents Instead auto add decimal places so that a usable value is shown when the unit is degrees and the setting for decimal places isn't sufficient to show a value.
qgis · Apr 7, 2017 · 29fd5cc · 29fd5cc
1 parent 4180837
commit 29fd5cc
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diff --git a/src/app/qgsmeasuredialog.cpp b/src/app/qgsmeasuredialog.cpp
@@ -274,7 +274,16 @@ QString QgsMeasureDialog::formatDistance( double distance, bool convertUnits ) c
 
   if ( convertUnits )
     distance = convertLength( distance, mDistanceUnits );
-  return QgsDistanceArea::formatDistance( distance, mDecimalPlaces, mDistanceUnits, baseUnit );
+
+  int decimals = mDecimalPlaces;
+  if ( mDistanceUnits == QgsUnitTypes::DistanceDegrees  && distance < 1 )
+  {
+    // special handling for degrees - because we can't use smaller units (eg m->mm), we need to make sure there's
+    // enough decimal places to show a usable measurement value
+    int minPlaces = qRound( log10( 1.0 / distance ) ) + 1;
+    decimals = qMax( decimals, minPlaces );
+  }
+  return QgsDistanceArea::formatDistance( distance, decimals, mDistanceUnits, baseUnit );
 }
 
 QString QgsMeasureDialog::formatArea( double area, bool convertUnits ) const

diff --git a/tests/src/app/testqgsmeasuretool.cpp b/tests/src/app/testqgsmeasuretool.cpp
@@ -43,6 +43,7 @@ class TestQgsMeasureTool : public QObject
     void testLengthCalculation();
     void testLengthCalculationNoCrs();
     void testAreaCalculation();
+    void degreeDecimalPlaces();
 
   private:
     QgisApp *mQgisApp = nullptr;
@@ -227,5 +228,24 @@ void TestQgsMeasureTool::testAreaCalculation()
   QGSCOMPARENEAR( measured, expected, 0.001 );
 }
 
+void TestQgsMeasureTool::degreeDecimalPlaces()
+{
+  QgsProject::instance()->setDistanceUnits( QgsUnitTypes::DistanceDegrees );
+
+  QgsSettings s;
+  s.setValue( QStringLiteral( "qgis/measure/decimalplaces" ), 3 );
+
+  std::unique_ptr< QgsMeasureTool > tool( new QgsMeasureTool( mCanvas, true ) );
+  std::unique_ptr< QgsMeasureDialog > dlg( new QgsMeasureDialog( tool.get() ) );
+
+  QCOMPARE( dlg->formatDistance( 11, false ), QString( "11.000 deg" ) );
+  QCOMPARE( dlg->formatDistance( 0.005, false ), QString( "0.005 deg" ) );
+  QCOMPARE( dlg->formatDistance( 0.002, false ), QString( "0.0020 deg" ) );
+  QCOMPARE( dlg->formatDistance( 0.001, false ), QString( "0.0010 deg" ) );
+  QCOMPARE( dlg->formatDistance( 0.0001, false ), QString( "0.00010 deg" ) );
+  QCOMPARE( dlg->formatDistance( 0.00001, false ), QString( "0.000010 deg" ) );
+
+}
+
 QGSTEST_MAIN( TestQgsMeasureTool )
 #include "testqgsmeasuretool.moc"