Hopefully fix raster layers not rendering on Windows

The copy constructor for QgsContrastEnhancement was using
an uninitialized value for the mContrastEnhancementAlgorithm
member, resulting in no contrast function being set in
certain occasions.

Refs #13155

Author: nyalldawson

src/core/raster/qgscontrastenhancement.cpp

@@ -29,13 +29,12 @@ class originally created circa 2004 by T.Sutton, Gary E.Sherman, Steve Halasz
 #include <QDomElement>
 
 QgsContrastEnhancement::QgsContrastEnhancement( QGis::DataType theDataType )
+    : mContrastEnhancementAlgorithm( NoEnhancement )
+    , mContrastEnhancementFunction( nullptr )
+    , mEnhancementDirty( false )
+    , mLookupTable( nullptr )
+    , mRasterDataType( theDataType )
 {
-  mLookupTable = nullptr;
-  mContrastEnhancementFunction = nullptr;
-  mEnhancementDirty = false;
-  mContrastEnhancementAlgorithm = NoEnhancement;
-  mRasterDataType = theDataType;
-
   mMinimumValue = minimumValuePossible( mRasterDataType );
   mMaximumValue = maximumValuePossible( mRasterDataType );
   mRasterDataTypeRange = mMaximumValue - mMinimumValue;
@@ -53,16 +52,14 @@ QgsContrastEnhancement::QgsContrastEnhancement( QGis::DataType theDataType )
 }
 
 QgsContrastEnhancement::QgsContrastEnhancement( const QgsContrastEnhancement& ce )
+    : mContrastEnhancementFunction( nullptr )
+    , mEnhancementDirty( true )
+    , mLookupTable( nullptr )
+    , mMinimumValue( ce.mMinimumValue )
+    , mMaximumValue( ce.mMaximumValue )
+    , mRasterDataType( ce.mRasterDataType )
+    , mRasterDataTypeRange( ce.mRasterDataTypeRange )
 {
-  mLookupTable = nullptr;
-  mContrastEnhancementFunction = nullptr;
-  mEnhancementDirty = true;
-  mRasterDataType = ce.mRasterDataType;
-
-  mMinimumValue = ce.mMinimumValue;
-  mMaximumValue = ce.mMaximumValue;
-  mRasterDataTypeRange = ce.mRasterDataTypeRange;
-
   mLookupTableOffset = minimumValuePossible( mRasterDataType ) * -1;
 
   // setContrastEnhancementAlgorithm sets also QgsContrastEnhancementFunction
@@ -230,7 +227,6 @@ bool QgsContrastEnhancement::generateLookupTable()
 */
 bool QgsContrastEnhancement::isValueInDisplayableRange( double theValue )
 {
-
   if ( mContrastEnhancementFunction )
   {
     return mContrastEnhancementFunction->isValueInDisplayableRange( theValue );
@@ -247,40 +243,35 @@ bool QgsContrastEnhancement::isValueInDisplayableRange( double theValue )
 */
 void QgsContrastEnhancement::setContrastEnhancementAlgorithm( ContrastEnhancementAlgorithm theAlgorithm, bool generateTable )
 {
-  QgsDebugMsg( "called algorithm: " + QString::number( static_cast< int >( theAlgorithm ) ) + " generate lookup table: " + QString::number( static_cast< int >( generateTable ) ) );
-
-  if ( theAlgorithm != mContrastEnhancementAlgorithm )
+  switch ( theAlgorithm )
   {
-    switch ( theAlgorithm )
-    {
-      case StretchToMinimumMaximum :
-        delete mContrastEnhancementFunction;
-        mContrastEnhancementFunction = new QgsLinearMinMaxEnhancement( mRasterDataType, mMinimumValue, mMaximumValue );
-        break;
-      case StretchAndClipToMinimumMaximum :
-        delete mContrastEnhancementFunction;
-        mContrastEnhancementFunction = new QgsLinearMinMaxEnhancementWithClip( mRasterDataType, mMinimumValue, mMaximumValue );
-        break;
-      case ClipToMinimumMaximum :
-        delete mContrastEnhancementFunction;
-        mContrastEnhancementFunction = new QgsClipToMinMaxEnhancement( mRasterDataType, mMinimumValue, mMaximumValue );
-        break;
-      case UserDefinedEnhancement :
-        //Do nothing
-        break;
-      default:
-        delete mContrastEnhancementFunction;
-        mContrastEnhancementFunction = new QgsContrastEnhancementFunction( mRasterDataType, mMinimumValue, mMaximumValue );
-        break;
-    }
+    case StretchToMinimumMaximum :
+      delete mContrastEnhancementFunction;
+      mContrastEnhancementFunction = new QgsLinearMinMaxEnhancement( mRasterDataType, mMinimumValue, mMaximumValue );
+      break;
+    case StretchAndClipToMinimumMaximum :
+      delete mContrastEnhancementFunction;
+      mContrastEnhancementFunction = new QgsLinearMinMaxEnhancementWithClip( mRasterDataType, mMinimumValue, mMaximumValue );
+      break;
+    case ClipToMinimumMaximum :
+      delete mContrastEnhancementFunction;
+      mContrastEnhancementFunction = new QgsClipToMinMaxEnhancement( mRasterDataType, mMinimumValue, mMaximumValue );
+      break;
+    case UserDefinedEnhancement :
+      //Do nothing
+      break;
+    default:
+      delete mContrastEnhancementFunction;
+      mContrastEnhancementFunction = new QgsContrastEnhancementFunction( mRasterDataType, mMinimumValue, mMaximumValue );
+      break;
+  }
 
-    mEnhancementDirty = true;
-    mContrastEnhancementAlgorithm = theAlgorithm;
+  mEnhancementDirty = true;
+  mContrastEnhancementAlgorithm = theAlgorithm;
 
-    if ( generateTable )
-    {
-      generateLookupTable();
-    }
+  if ( generateTable )
+  {
+    generateLookupTable();
   }
 }