[mesh] make layer blend mode option visible in UI

src/app/mesh/qgsrenderermeshpropertieswidget.cpp

@@ -44,6 +44,10 @@ QgsRendererMeshPropertiesWidget::QgsRendererMeshPropertiesWidget( QgsMeshLayer *
   mMeshRendererVectorSettingsWidget->setLayer( mMeshLayer );
   syncToLayer();
 
+  //blend mode
+  mBlendModeComboBox->setBlendMode( mMeshLayer->blendMode() );
+  connect( mBlendModeComboBox, static_cast<void ( QComboBox::* )( int )>( &QComboBox::currentIndexChanged ), this, &QgsPanelWidget::widgetChanged );
+
   connect( mMeshRendererActiveDatasetWidget, &QgsMeshRendererActiveDatasetWidget::activeScalarGroupChanged,
            this, &QgsRendererMeshPropertiesWidget::onActiveScalarGroupChanged );
   connect( mMeshRendererActiveDatasetWidget, &QgsMeshRendererActiveDatasetWidget::activeVectorGroupChanged,
@@ -53,7 +57,6 @@ QgsRendererMeshPropertiesWidget::QgsRendererMeshPropertiesWidget( QgsMeshLayer *
   connect( mTriangularMeshGroup, &QGroupBox::toggled, this, &QgsPanelWidget::widgetChanged );
   connect( mContoursGroupBox, &QGroupBox::toggled, this, &QgsPanelWidget::widgetChanged );
   connect( mVectorsGroupBox, &QGroupBox::toggled, this, &QgsPanelWidget::widgetChanged );
-
   connect( mMeshRendererActiveDatasetWidget, &QgsMeshRendererActiveDatasetWidget::widgetChanged, this, &QgsPanelWidget::widgetChanged );
   connect( mMeshRendererScalarSettingsWidget, &QgsMeshRendererScalarSettingsWidget::widgetChanged, this, &QgsPanelWidget::widgetChanged );
   connect( mMeshRendererVectorSettingsWidget, &QgsMeshRendererVectorSettingsWidget::widgetChanged, this, &QgsPanelWidget::widgetChanged );
@@ -100,6 +103,9 @@ void QgsRendererMeshPropertiesWidget::apply()
   if ( activeVectorDatasetIndex.isValid() )
     settings.setVectorSettings( activeVectorDatasetIndex.group(), mMeshRendererVectorSettingsWidget->settings() );
 
+  //set the blend mode for the layer
+  mMeshLayer->setBlendMode( mBlendModeComboBox->blendMode() );
+
   mMeshLayer->setRendererSettings( settings );
   mMeshLayer->triggerRepaint();
 }

src/core/mesh/qgsmeshlayer.cpp

@@ -27,6 +27,7 @@
 #include "qgsmeshlayer.h"
 #include "qgsmeshlayerrenderer.h"
 #include "qgsmeshlayerutils.h"
+#include "qgspainting.h"
 #include "qgsproviderregistry.h"
 #include "qgsreadwritecontext.h"
 #include "qgsstyle.h"
@@ -271,6 +272,14 @@ bool QgsMeshLayer::readSymbology( const QDomNode &node, QString &errorMessage,
   if ( !elemRendererSettings.isNull() )
     mRendererSettings.readXml( elemRendererSettings );
 
+  // get and set the blend mode if it exists
+  QDomNode blendModeNode = node.namedItem( QStringLiteral( "blendMode" ) );
+  if ( !blendModeNode.isNull() )
+  {
+    QDomElement e = blendModeNode.toElement();
+    setBlendMode( QgsPainting::getCompositionMode( static_cast< QgsPainting::BlendMode >( e.text().toInt() ) ) );
+  }
+
   return true;
 }
 
@@ -287,6 +296,12 @@ bool QgsMeshLayer::writeSymbology( QDomNode &node, QDomDocument &doc, QString &e
   QDomElement elemRendererSettings = mRendererSettings.writeXml( doc );
   elem.appendChild( elemRendererSettings );
 
+  // add blend mode node
+  QDomElement blendModeElement  = doc.createElement( QStringLiteral( "blendMode" ) );
+  QDomText blendModeText = doc.createTextNode( QString::number( QgsPainting::getBlendModeEnum( blendMode() ) ) );
+  blendModeElement.appendChild( blendModeText );
+  node.appendChild( blendModeElement );
+
   return true;
 }
 

src/ui/mesh/qgsrenderermeshpropswidgetbase.ui

@@ -68,6 +68,32 @@
          </property>
         </widget>
        </item>
+      <item>
+       <widget class="QgsCollapsibleGroupBox" name="mActiveDatasetBlendingMode">
+        <property name="title">
+         <string>Layer Rendering</string>
+        </property>
+        <layout class="QHBoxLayout" name="horizontalLayout">
+         <item>
+          <widget class="QLabel" name="">
+           <property name="text">
+            <string>Blending mode</string>
+           </property>
+          </widget>
+         </item>
+         <item>
+          <widget class="QgsBlendModeComboBox" name="mBlendModeComboBox">
+           <property name="minimumSize">
+            <size>
+             <width>0</width>
+             <height>0</height>
+            </size>
+           </property>
+          </widget>
+         </item>
+        </layout>
+       </widget>
+      </item>
        <item>
         <spacer name="verticalSpacer_3">
          <property name="orientation">
@@ -299,6 +325,17 @@
    <header>mesh/qgsmeshrenderervectorsettingswidget.h</header>
    <container>1</container>
   </customwidget>
+  <customwidget>
+   <class>QgsBlendModeComboBox</class>
+   <extends>QComboBox</extends>
+   <header>qgsblendmodecombobox.h</header>
+  </customwidget>
+  <customwidget>
+   <class>QgsCollapsibleGroupBox</class>
+   <extends>QGroupBox</extends>
+   <header>qgscollapsiblegroupbox.h</header>
+   <container>1</container>
+  </customwidget>
  </customwidgets>
  <resources>
   <include location="../../../images/images.qrc"/>