Merge pull request #43927 from mhugent/raster_legend_placeholder_icon

Feature: possibility to use placeholder icon in legend for raster layer. funded by [Canton of Glarus] [https://www.gl.ch/verwaltung/bau-und-umwelt/hochbau/raumentwicklung-und-geoinformation/geoportal-kanton-glarus.html/808]

python/core/auto_generated/qgsmaplayer.sip.in

@@ -1429,6 +1429,24 @@ Returns the layer's temporal properties. This may be ``None``, depending on the
 Returns the layer's elevation properties. This may be ``None``, depending on the layer type.
 
 .. versionadded:: 3.18
+%End
+
+    QString legendPlaceholderImage() const;
+%Docstring
+Returns path to the placeholder image or an empty string if a generated legend is shown
+
+:return: placholder image path
+
+.. versionadded:: 3.22
+%End
+
+    void setLegendPlaceholderImage( const QString &imgPath );
+%Docstring
+Set placeholder image for legend. If the string is empty, a generated legend will be shown.
+
+:param imgPath: file path to the placeholder image
+
+.. versionadded:: 3.22
 %End
 
   public slots:

src/core/layertree/qgslayertreemodellegendnode.cpp

@@ -946,19 +946,23 @@ QSizeF QgsImageLegendNode::drawSymbol( const QgsLegendSettings &settings, ItemCo
 {
   Q_UNUSED( itemHeight )
 
-  if ( ctx && ctx->painter )
+  if ( ctx && ctx->painter && ctx->context )
   {
+    QgsScopedRenderContextScaleToPixels scopedScaleToPixels( *( ctx->context ) );
+    double scaleFactor = ctx->context->scaleFactor();
+    double imgWidth = settings.wmsLegendSize().width() * scaleFactor;
+    double imgHeight = settings.wmsLegendSize().height() * scaleFactor;
+
+    QImage scaledImg = mImage.scaled( QSizeF( imgWidth, imgHeight ).toSize(), Qt::KeepAspectRatio, Qt::SmoothTransformation );
     switch ( settings.symbolAlignment() )
     {
       case Qt::AlignLeft:
       default:
-        ctx->painter->drawImage( QRectF( ctx->columnLeft, ctx->top, settings.wmsLegendSize().width(), settings.wmsLegendSize().height() ),
-                                 mImage, QRectF( 0, 0, mImage.width(), mImage.height() ) );
+        ctx->painter->drawImage( QPointF( ctx->columnLeft * scaleFactor, ctx->top * scaleFactor ), scaledImg );
         break;
 
       case Qt::AlignRight:
-        ctx->painter->drawImage( QRectF( ctx->columnRight - settings.wmsLegendSize().width(), ctx->top, settings.wmsLegendSize().width(), settings.wmsLegendSize().height() ),
-                                 mImage, QRectF( 0, 0, mImage.width(), mImage.height() ) );
+        ctx->painter->drawImage( QPointF( ctx->columnRight * scaleFactor - imgWidth, ctx->top * scaleFactor ), scaledImg );
         break;
     }
   }

src/core/qgsmaplayer.cpp

@@ -406,6 +406,8 @@ bool QgsMapLayer::readLayerXml( const QDomElement &layerElement, QgsReadWriteCon
       mWgs84Extent = QgsXmlUtils::readRectangle( wgs84ExtentNode.toElement() );
   }
 
+  mLegendPlaceholderImage = layerElement.attribute( QStringLiteral( "legendPlaceholderImage" ) );
+
   return ! layerError;
 } // bool QgsMapLayer::readLayerXML
 
@@ -576,6 +578,8 @@ bool QgsMapLayer::writeLayerXml( QDomElement &layerElement, QDomDocument &docume
   mMetadata.writeMetadataXml( myMetadataElem, document );
   layerElement.appendChild( myMetadataElem );
 
+  layerElement.setAttribute( QStringLiteral( "legendPlaceholderImage" ), mLegendPlaceholderImage );
+
   // now append layer node to map layer node
   return writeXml( layerElement, document, context );
 }

src/core/qgsmaplayer.h

@@ -1279,6 +1279,20 @@ class CORE_EXPORT QgsMapLayer : public QObject
      */
     virtual QgsMapLayerElevationProperties *elevationProperties() { return nullptr; }
 
+    /**
+     * Returns path to the placeholder image or an empty string if a generated legend is shown
+     * \return placholder image path
+     * \since QGIS 3.22
+     */
+    QString legendPlaceholderImage() const { return mLegendPlaceholderImage;}
+
+    /**
+     * Set placeholder image for legend. If the string is empty, a generated legend will be shown.
+     * \param imgPath file path to the placeholder image
+     * \since QGIS 3.22
+     */
+    void setLegendPlaceholderImage( const QString &imgPath ) { mLegendPlaceholderImage = imgPath; }
+
   public slots:
 
     /**
@@ -1867,6 +1881,9 @@ class CORE_EXPORT QgsMapLayer : public QObject
     //! To avoid firing multiple time repaintRequested signal on circular layer circular dependencies
     bool mRepaintRequestedFired = false;
 
+    //! Path to placeholder image for layer legend. If the string is empty, a generated legend is shown
+    QString mLegendPlaceholderImage;
+
     friend class QgsVectorLayer;
 };
 

src/core/qgsmaplayerlegend.cpp

@@ -14,7 +14,8 @@
  ***************************************************************************/
 
 #include "qgsmaplayerlegend.h"
-
+#include "qgsiconutils.h"
+#include "qgsimagecache.h"
 #include "qgssettings.h"
 #include "qgslayertree.h"
 #include "qgslayertreemodellegendnode.h"
@@ -359,6 +360,18 @@ QList<QgsLayerTreeModelLegendNode *> QgsDefaultVectorLayerLegend::createLayerTre
 {
   QList<QgsLayerTreeModelLegendNode *> nodes;
 
+  if ( mLayer )
+  {
+    QString placeholderImage = mLayer->legendPlaceholderImage();
+    if ( !placeholderImage.isEmpty() )
+    {
+      bool fitsInCache;
+      QImage img = QgsApplication::imageCache()->pathAsImage( placeholderImage, QSize(), false, 1.0, fitsInCache );
+      nodes << new QgsImageLegendNode( nodeLayer, img );
+      return nodes;
+    }
+  }
+
   QgsFeatureRenderer *r = mLayer->renderer();
   if ( !r )
     return nodes;
@@ -502,7 +515,14 @@ QList<QgsLayerTreeModelLegendNode *> QgsDefaultRasterLayerLegend::createLayerTre
     nodes << new QgsWmsLegendNode( nodeLayer );
   }
 
-  if ( mLayer->renderer() )
+  QString placeholderImage = mLayer->legendPlaceholderImage();
+  if ( !placeholderImage.isEmpty() )
+  {
+    bool fitsInCache;
+    QImage img = QgsApplication::imageCache()->pathAsImage( placeholderImage, QSize(), false, 1.0, fitsInCache );
+    nodes << new QgsImageLegendNode( nodeLayer, img );
+  }
+  else if ( mLayer->renderer() )
     nodes.append( mLayer->renderer()->createLegendNodes( nodeLayer ) );
   return nodes;
 }

src/gui/raster/qgsrasterlayerproperties.cpp

@@ -914,6 +914,8 @@ void QgsRasterLayerProperties::sync()
   QVariant wmsBackgroundLayer = mRasterLayer->customProperty( QStringLiteral( "WMSBackgroundLayer" ), false );
   mBackgroundLayerCheckBox->setChecked( wmsBackgroundLayer.toBool() );
 
+  mLegendPlaceholderWidget->setLastPathSettingsKey( QStringLiteral( "lastLegendPlaceholderDir" ) );
+  mLegendPlaceholderWidget->setSource( mRasterLayer->legendPlaceholderImage() );
   mLegendConfigEmbeddedWidget->setLayer( mRasterLayer );
 
   mTemporalWidget->syncToLayer();
@@ -946,6 +948,7 @@ void QgsRasterLayerProperties::apply()
   /*
    * Legend Tab
    */
+  mRasterLayer->setLegendPlaceholderImage( mLegendPlaceholderWidget->source() );
   mLegendConfigEmbeddedWidget->applyToLayer();
 
   QgsDebugMsgLevel( QStringLiteral( "apply processing symbology tab" ), 3 );

src/gui/vector/qgsvectorlayerlegendwidget.cpp

@@ -21,6 +21,7 @@
 #include <QTreeWidget>
 
 #include "qgsexpressionbuilderdialog.h"
+#include "qgsfilecontentsourcelineedit.h"
 #include "qgsmapcanvas.h"
 #include "qgsmaplayerlegend.h"
 #include "qgsrenderer.h"
@@ -71,10 +72,19 @@ QgsVectorLayerLegendWidget::QgsVectorLayerLegendWidget( QWidget *parent )
   labelLegendLayout->addWidget( mLabelLegendTreeWidget );
   mLabelLegendGroupBox->setLayout( labelLegendLayout );
 
+  mPlaceholderImageLabel = new QLabel( tr( "Legend placeholder image" ) );
+  mImageSourceLineEdit = new QgsImageSourceLineEdit();
+  mImageSourceLineEdit->setLastPathSettingsKey( QStringLiteral( "lastLegendPlaceholderDir" ) );
+  if ( mLayer )
+  {
+    mImageSourceLineEdit->setSource( mLayer->legendPlaceholderImage() );
+  }
 
 
   QVBoxLayout *layout = new QVBoxLayout;
   layout->setContentsMargins( 0, 0, 0, 0 );
+  layout->addWidget( mPlaceholderImageLabel );
+  layout->addWidget( mImageSourceLineEdit );
   layout->addWidget( mShowLabelLegendCheckBox );
   layout->addWidget( mLabelLegendGroupBox );
   layout->addWidget( mTextOnSymbolGroupBox );
@@ -122,7 +132,10 @@ void QgsVectorLayerLegendWidget::setLayer( QgsVectorLayer *layer )
   mTextOnSymbolGroupBox->setChecked( legend->textOnSymbolEnabled() );
   mTextOnSymbolFormatButton->setTextFormat( legend->textOnSymbolTextFormat() );
   populateLegendTreeView( legend->textOnSymbolContent() );
-
+  if ( mLayer )
+  {
+    mImageSourceLineEdit->setSource( mLayer->legendPlaceholderImage() );
+  }
 }
 
 void QgsVectorLayerLegendWidget::populateLabelLegendTreeWidget()
@@ -221,6 +234,8 @@ void QgsVectorLayerLegendWidget::applyToLayer()
     applyLabelLegend();
   }
 
+  mLayer->setLegendPlaceholderImage( mImageSourceLineEdit->source() );
+
   mLayer->setLegend( legend );
 }
 

src/gui/vector/qgsvectorlayerlegendwidget.h

@@ -25,6 +25,7 @@
 #include "qgis_gui.h"
 
 class QCheckBox;
+class QgsImageSourceLineEdit;
 class QLabel;
 class QPushButton;
 class QTreeView;
@@ -76,6 +77,8 @@ class GUI_EXPORT QgsVectorLayerLegendWidget : public QWidget
     QCheckBox *mShowLabelLegendCheckBox = nullptr;
     QgsCollapsibleGroupBox *mLabelLegendGroupBox = nullptr;
     QTreeWidget *mLabelLegendTreeWidget = nullptr;
+    QLabel *mPlaceholderImageLabel = nullptr;
+    QgsImageSourceLineEdit *mImageSourceLineEdit = nullptr;
 
     QgsMapCanvas *mCanvas = nullptr;
     QgsVectorLayer *mLayer = nullptr;

src/ui/qgsrasterlayerpropertiesbase.ui

@@ -254,7 +254,7 @@
           </sizepolicy>
          </property>
          <property name="currentIndex">
-          <number>1</number>
+          <number>0</number>
          </property>
          <widget class="QWidget" name="mOptsPage_Information">
           <layout class="QVBoxLayout" name="verticalLayout_20">
@@ -299,8 +299,8 @@
                <rect>
                 <x>0</x>
                 <y>0</y>
-                <width>643</width>
-                <height>679</height>
+                <width>650</width>
+                <height>673</height>
                </rect>
               </property>
               <layout class="QVBoxLayout" name="verticalLayout_7">
@@ -1563,8 +1563,8 @@ border-radius: 2px;</string>
                <rect>
                 <x>0</x>
                 <y>0</y>
-                <width>577</width>
-                <height>190</height>
+                <width>650</width>
+                <height>673</height>
                </rect>
               </property>
               <layout class="QVBoxLayout" name="verticalLayout_12">
@@ -1633,8 +1633,8 @@ border-radius: 2px;</string>
                        <string>&lt;!DOCTYPE HTML PUBLIC &quot;-//W3C//DTD HTML 4.0//EN&quot; &quot;http://www.w3.org/TR/REC-html40/strict.dtd&quot;&gt;
 &lt;html&gt;&lt;head&gt;&lt;meta name=&quot;qrichtext&quot; content=&quot;1&quot; /&gt;&lt;style type=&quot;text/css&quot;&gt;
 p, li { white-space: pre-wrap; }
-&lt;/style&gt;&lt;/head&gt;&lt;body style=&quot; font-family:'Fira Sans'; font-size:11pt; font-weight:400; font-style:normal;&quot;&gt;
-&lt;p style=&quot; margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;&quot;&gt;&lt;span style=&quot; font-family:'Cantarell';&quot;&gt;&lt;br /&gt;&lt;/span&gt;&lt;/p&gt;&lt;/body&gt;&lt;/html&gt;</string>
+&lt;/style&gt;&lt;/head&gt;&lt;body style=&quot; font-family:'Noto Sans'; font-size:12pt; font-weight:400; font-style:normal;&quot;&gt;
+&lt;p style=&quot; margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;&quot;&gt;&lt;span style=&quot; font-family:'Cantarell'; font-size:11pt;&quot;&gt;&lt;br /&gt;&lt;/span&gt;&lt;/p&gt;&lt;/body&gt;&lt;/html&gt;</string>
                       </property>
                      </widget>
                     </item>
@@ -1739,21 +1739,15 @@ p, li { white-space: pre-wrap; }
           </layout>
          </widget>
          <widget class="QWidget" name="mOptsPage_Legend">
-          <layout class="QVBoxLayout" name="verticalLayout_18">
-           <property name="leftMargin">
-            <number>0</number>
-           </property>
-           <property name="topMargin">
-            <number>0</number>
-           </property>
-           <property name="rightMargin">
-            <number>0</number>
-           </property>
-           <property name="bottomMargin">
-            <number>0</number>
-           </property>
-           <item>
+          <layout class="QGridLayout" name="gridLayout_15">
+           <item row="2" column="0">
             <widget class="QGroupBox" name="groupBox">
+             <property name="sizePolicy">
+              <sizepolicy hsizetype="Preferred" vsizetype="Expanding">
+               <horstretch>0</horstretch>
+               <verstretch>0</verstretch>
+              </sizepolicy>
+             </property>
              <property name="title">
               <string>Embedded Widgets in Legend</string>
              </property>
@@ -1764,6 +1758,16 @@ p, li { white-space: pre-wrap; }
              </layout>
             </widget>
            </item>
+           <item row="1" column="0">
+            <widget class="QgsImageSourceLineEdit" name="mLegendPlaceholderWidget" native="true"/>
+           </item>
+           <item row="0" column="0">
+            <widget class="QLabel" name="mLegendPlaceholderLabel">
+             <property name="text">
+              <string>Legend placeholder image</string>
+             </property>
+            </widget>
+           </item>
           </layout>
          </widget>
          <widget class="QWidget" name="mOptsPage_Server">
@@ -1793,8 +1797,8 @@ p, li { white-space: pre-wrap; }
                <rect>
                 <x>0</x>
                 <y>0</y>
-                <width>343</width>
-                <height>684</height>
+                <width>629</width>
+                <height>793</height>
                </rect>
               </property>
               <layout class="QGridLayout" name="gridLayout_12">
@@ -2315,6 +2319,23 @@ p, li { white-space: pre-wrap; }
    <extends>QComboBox</extends>
    <header>qgsblendmodecombobox.h</header>
   </customwidget>
+  <customwidget>
+   <class>QgsOpacityWidget</class>
+   <extends>QWidget</extends>
+   <header>qgsopacitywidget.h</header>
+   <container>1</container>
+  </customwidget>
+  <customwidget>
+   <class>QgsRasterBandComboBox</class>
+   <extends>QComboBox</extends>
+   <header>qgsrasterbandcombobox.h</header>
+  </customwidget>
+  <customwidget>
+   <class>QgsImageSourceLineEdit</class>
+   <extends>QWidget</extends>
+   <header>qgsfilecontentsourcelineedit.h</header>
+   <container>1</container>
+  </customwidget>
  </customwidgets>
  <tabstops>
   <tabstop>mSearchLineEdit</tabstop>

tests/src/python/test_qgsserver_wms_getlegendgraphic.py

@@ -1045,6 +1045,19 @@ class TestQgsServerWMSGetLegendGraphic(TestQgsServerWMSTestBase):
         self.assertEqual(node['scaleMaxDenom'], 1000)
         self.assertEqual(node['scaleMinDenom'], 10000)
 
+    def testLegendPlaceholderIcon(self):
+        qs = "?" + "&".join(["%s=%s" % i for i in list({
+            "MAP": self.testdata_path + 'test_project_legend_placeholder_image.qgs',
+            "SERVICE": "WMS",
+            "VERSION": "1.3",
+            "REQUEST": "GetLegendGraphic",
+            "LAYER": "landsat",
+            "FORMAT": "image/png",
+        }.items())])
+
+        r, h = self._result(self._execute_request(qs))
+        self._img_diff_error(r, h, "WMS_GetLegendGraphic_Legend_Placeholder_Icon")
+
 
 if __name__ == '__main__':
     unittest.main()