From cb7838badc85d423be1281e8e66788d9070d6b12 Mon Sep 17 00:00:00 2001
From: Nyall Dawson <nyall.dawson@gmail.com>
Date: Tue, 22 Jan 2019 11:53:35 +1000
Subject: [PATCH] Silently alias old "$scale" expression function to
 "@map_scale" (when available)

Allows older projects to open without change. We still hide $scale from the
builder UI, as we eventually want to clamp out its use.
---
 src/core/expression/qgsexpressionfunction.cpp | 21 +++++-
 tests/src/core/testqgsmapsettings.cpp         | 67 +++++++++++++++++++
 2 files changed, 87 insertions(+), 1 deletion(-)

diff --git a/src/core/expression/qgsexpressionfunction.cpp b/src/core/expression/qgsexpressionfunction.cpp
index dbadf4e5d6b..21a87e5b237 100644
--- a/src/core/expression/qgsexpressionfunction.cpp
+++ b/src/core/expression/qgsexpressionfunction.cpp
@@ -889,6 +889,22 @@ static QVariant fcnAggregateArray( const QVariantList &values, const QgsExpressi
   return fcnAggregateGeneric( QgsAggregateCalculator::ArrayAggregate, values, QgsAggregateCalculator::AggregateParameters(), context, parent );
 }
 
+static QVariant fcnMapScale( const QVariantList &, const QgsExpressionContext *context, QgsExpression *, const QgsExpressionNodeFunction * )
+{
+  if ( !context )
+    return QVariant();
+
+  QVariant scale = context->variable( QStringLiteral( "map_scale" ) );
+  bool ok = false;
+  if ( !scale.isValid() || scale.isNull() )
+    return QVariant();
+
+  const double v = scale.toDouble( &ok );
+  if ( ok )
+    return v;
+  return QVariant();
+}
+
 static QVariant fcnClamp( const QVariantList &values, const QgsExpressionContext *, QgsExpression *parent, const QgsExpressionNodeFunction * )
 {
   double minValue = QgsExpressionUtils::getDoubleValue( values.at( 0 ), parent );
@@ -4877,7 +4893,10 @@ const QList<QgsExpressionFunction *> &QgsExpression::Functions()
         << new QgsStaticExpressionFunction( QStringLiteral( "color_part" ), 2, fncColorPart, QStringLiteral( "Color" ) )
         << new QgsStaticExpressionFunction( QStringLiteral( "darker" ), 2, fncDarker, QStringLiteral( "Color" ) )
         << new QgsStaticExpressionFunction( QStringLiteral( "lighter" ), 2, fncLighter, QStringLiteral( "Color" ) )
-        << new QgsStaticExpressionFunction( QStringLiteral( "set_color_part" ), 3, fncSetColorPart, QStringLiteral( "Color" ) );
+        << new QgsStaticExpressionFunction( QStringLiteral( "set_color_part" ), 3, fncSetColorPart, QStringLiteral( "Color" ) )
+
+        // deprecated stuff - hidden from users
+        << new QgsStaticExpressionFunction( QStringLiteral( "$scale" ), QgsExpressionFunction::ParameterList(), fcnMapScale, QStringLiteral( "deprecated" ) );
 
     QgsStaticExpressionFunction *geomFunc = new QgsStaticExpressionFunction( QStringLiteral( "$geometry" ), 0, fcnGeometry, QStringLiteral( "GeometryGroup" ), QString(), true );
     geomFunc->setIsStatic( false );
diff --git a/tests/src/core/testqgsmapsettings.cpp b/tests/src/core/testqgsmapsettings.cpp
index 26cb6200d9c..30e44e14255 100644
--- a/tests/src/core/testqgsmapsettings.cpp
+++ b/tests/src/core/testqgsmapsettings.cpp
@@ -46,6 +46,7 @@ class TestQgsMapSettings: public QObject
     void testXmlReadWrite();
     void testSetLayers();
     void testLabelBoundary();
+    void testExpressionContext();
 
   private:
     QString toString( const QPolygonF &p, int decimalPlaces = 2 ) const;
@@ -376,5 +377,71 @@ void TestQgsMapSettings::testLabelBoundary()
   QCOMPARE( ms.labelBoundaryGeometry().asWkt(), QStringLiteral( "Polygon ((0 0, 1 0, 1 1, 0 1, 0 0))" ) );
 }
 
+void TestQgsMapSettings::testExpressionContext()
+{
+  QgsMapSettings ms;
+  QgsExpressionContext c;
+  QVariant r;
+
+  ms.setOutputSize( QSize( 5000, 5000 ) );
+  ms.setExtent( QgsRectangle( -1, 0, 2, 2 ) );
+  ms.setDestinationCrs( QgsCoordinateReferenceSystem( QStringLiteral( "EPSG:4326" ) ) );
+  ms.setRotation( -32 );
+  c << QgsExpressionContextUtils::mapSettingsScope( ms );
+
+  QgsExpression e( QStringLiteral( "@map_scale" ) );
+  r = e.evaluate( &c );
+  QGSCOMPARENEAR( r.toDouble(), 247990, 10 );
+
+  // The old $scale function should silently map to @map_scale, so that older projects work without change
+  e = QgsExpression( QStringLiteral( "$scale" ) );
+  r = e.evaluate( &c );
+  QGSCOMPARENEAR( r.toDouble(), 247990, 10 );
+
+  // no map settings scope -- $scale is meaningless
+  e = QgsExpression( QStringLiteral( "$scale" ) );
+  r = e.evaluate( nullptr );
+  QVERIFY( !r.isValid() );
+
+  e = QgsExpression( QStringLiteral( "@map_id" ) );
+  r = e.evaluate( &c );
+  QCOMPARE( r.toString(), QStringLiteral( "canvas" ) );
+
+  e = QgsExpression( QStringLiteral( "@map_rotation" ) );
+  r = e.evaluate( &c );
+  QCOMPARE( r.toDouble(), -32.0 );
+
+  ms.setRotation( 0 );
+  c << QgsExpressionContextUtils::mapSettingsScope( ms );
+
+  e = QgsExpression( QStringLiteral( "geom_to_wkt( @map_extent )" ) );
+  r = e.evaluate( &c );
+  QCOMPARE( r.toString(), QStringLiteral( "Polygon ((-1 -0.5, 2 -0.5, 2 2.5, -1 2.5, -1 -0.5))" ) );
+
+  e = QgsExpression( QStringLiteral( "@map_extent_width" ) );
+  r = e.evaluate( &c );
+  QCOMPARE( r.toDouble(), 3 );
+
+  e = QgsExpression( QStringLiteral( "@map_extent_height" ) );
+  r = e.evaluate( &c );
+  QCOMPARE( r.toDouble(), 3 );
+
+  e = QgsExpression( QStringLiteral( "geom_to_wkt( @map_extent_center )" ) );
+  r = e.evaluate( &c );
+  QCOMPARE( r.toString(), QStringLiteral( "Point (0.5 1)" ) );
+
+  e = QgsExpression( QStringLiteral( "@map_crs" ) );
+  r = e.evaluate( &c );
+  QCOMPARE( r.toString(), QStringLiteral( "EPSG:4326" ) );
+
+  e = QgsExpression( QStringLiteral( "@map_crs_definition" ) );
+  r = e.evaluate( &c );
+  QCOMPARE( r.toString(), QStringLiteral( "+proj=longlat +datum=WGS84 +no_defs" ) );
+
+  e = QgsExpression( QStringLiteral( "@map_units" ) );
+  r = e.evaluate( &c );
+  QCOMPARE( r.toString(), QStringLiteral( "degrees" ) );
+}
+
 QGSTEST_MAIN( TestQgsMapSettings )
 #include "testqgsmapsettings.moc"