Add new QgsColorRampLegendNode class for rendering a color ramp item …

…as a legend node

python/core/auto_generated/layertree/qgscolorramplegendnode.sip.in

@@ -0,0 +1,68 @@
+/************************************************************************
+ * This file has been generated automatically from                      *
+ *                                                                      *
+ * src/core/layertree/qgscolorramplegendnode.h                          *
+ *                                                                      *
+ * Do not edit manually ! Edit header and run scripts/sipify.pl again   *
+ ************************************************************************/
+
+
+
+class QgsColorRampLegendNode : QgsLayerTreeModelLegendNode
+{
+%Docstring
+A legend node which renders a color ramp.
+
+.. versionadded:: 3.18
+%End
+
+%TypeHeaderCode
+#include "qgscolorramplegendnode.h"
+%End
+  public:
+
+    QgsColorRampLegendNode( QgsLayerTreeLayer *nodeLayer, QgsColorRamp *ramp /Transfer/,
+                            const QString &minimumLabel, const QString &maximumLabel, QObject *parent /TransferThis/ = 0 );
+%Docstring
+Constructor for QgsColorRampLegendNode.
+
+:param nodeLayer: layer node
+:param ramp: color ramp to render in node. Ownership is transferred to the node.
+:param minimumLabel: label text to render for the minimum value in the ramp
+:param maximumLabel: label text to render for the maximum value in the ramp
+:param parent: attach a parent QObject to the legend node.
+%End
+
+    virtual QVariant data( int role ) const;
+
+    virtual QSizeF drawSymbol( const QgsLegendSettings &settings, ItemContext *ctx, double itemHeight ) const;
+
+
+    void setIconSize( QSize size );
+%Docstring
+Set the icon ``size``, which controls how large the ramp will render in a layer tree widget.
+
+.. seealso:: :py:func:`iconSize`
+%End
+
+    QSize iconSize() const;
+%Docstring
+Returns the icon size, which is how large the ramp will render in a layer tree widget.
+
+.. seealso:: :py:func:`setIconSize`
+%End
+
+    const QgsColorRamp *ramp() const;
+%Docstring
+Returns the color ramp used by the node.
+%End
+
+};
+
+/************************************************************************
+ * This file has been generated automatically from                      *
+ *                                                                      *
+ * src/core/layertree/qgscolorramplegendnode.h                          *
+ *                                                                      *
+ * Do not edit manually ! Edit header and run scripts/sipify.pl again   *
+ ************************************************************************/

python/core/auto_generated/layertree/qgslayertreemodellegendnode.sip.in

@@ -51,6 +51,7 @@ and customized look.
       WmsLegend,
       DataDefinedSizeLegend,
       EmbeddedWidget,
+      ColorRampLegend,
     };
 
     QgsLayerTreeLayer *layerNode() const;

python/core/core_auto.sip

@@ -363,6 +363,7 @@
 %Include auto_generated/labeling/qgspallabeling.sip
 %Include auto_generated/labeling/qgsrulebasedlabeling.sip
 %Include auto_generated/labeling/qgsvectorlayerlabeling.sip
+%Include auto_generated/layertree/qgscolorramplegendnode.sip
 %Include auto_generated/layertree/qgslayertree.sip
 %Include auto_generated/layertree/qgslayertreegroup.sip
 %Include auto_generated/layertree/qgslayertreelayer.sip

src/core/CMakeLists.txt

@@ -92,6 +92,7 @@ set(QGIS_CORE_SRCS
   effects/qgsshadoweffect.cpp
   effects/qgstransformeffect.cpp
 
+  layertree/qgscolorramplegendnode.cpp
   layertree/qgslayertreegroup.cpp
   layertree/qgslayertreelayer.cpp
   layertree/qgslayertreemodel.cpp
@@ -1235,6 +1236,7 @@ set(QGIS_CORE_HDRS
   labeling/qgsvectorlayerlabeling.h
   labeling/qgsvectorlayerlabelprovider.h
 
+  layertree/qgscolorramplegendnode.h
   layertree/qgslayertree.h
   layertree/qgslayertreegroup.h
   layertree/qgslayertreelayer.h

src/core/layertree/qgscolorramplegendnode.cpp

@@ -0,0 +1,223 @@
+/***************************************************************************
+  qgscolorramplegendnode.cpp
+  --------------------------------------
+  Date                 : December 2020
+  Copyright            : (C) 2020 by Nyall Dawson
+  Email                : nyall dot dawson at gmail dot com
+ ***************************************************************************
+ *                                                                         *
+ *   This program is free software; you can redistribute it and/or modify  *
+ *   it under the terms of the GNU General Public License as published by  *
+ *   the Free Software Foundation; either version 2 of the License, or     *
+ *   (at your option) any later version.                                   *
+ *                                                                         *
+ ***************************************************************************/
+
+#include "qgscolorramplegendnode.h"
+#include "qgslegendsettings.h"
+#include "qgslayertreemodel.h"
+#include "qgslayertreelayer.h"
+#include "qgssymbollayerutils.h"
+#include "qgsexpressioncontextutils.h"
+#include "qgstextrenderer.h"
+
+QgsColorRampLegendNode::QgsColorRampLegendNode( QgsLayerTreeLayer *nodeLayer, QgsColorRamp *ramp, const QString &minimumLabel, const QString &maximumLabel, QObject *parent )
+  : QgsLayerTreeModelLegendNode( nodeLayer, parent )
+  , mRamp( ramp )
+  , mMinimumLabel( minimumLabel )
+  , mMaximumLabel( maximumLabel )
+{
+  const int iconSize = QgsLayerTreeModel::scaleIconSize( 16 );
+  mIconSize = QSize( iconSize, iconSize * 6 );
+
+  connect( nodeLayer, &QObject::destroyed, this, [ = ]() { mLayerNode = nullptr; } );
+}
+
+const QgsColorRamp *QgsColorRampLegendNode::ramp() const
+{
+  return mRamp.get();
+}
+
+QVariant QgsColorRampLegendNode::data( int role ) const
+{
+  if ( role == Qt::DisplayRole )
+  {
+    return QString();
+  }
+  else if ( role == Qt::EditRole )
+  {
+    return QString();
+  }
+  else if ( role == Qt::DecorationRole )
+  {
+    if ( mPixmap.isNull() || mPixmap.size() != mIconSize )
+    {
+      QPixmap pix;
+
+      if ( mRamp )
+      {
+        pix = QgsSymbolLayerUtils::colorRampPreviewPixmap( mRamp.get(), mIconSize, 0, Qt::Vertical, true, false );
+      }
+      else
+      {
+        pix = QPixmap( mIconSize );
+        pix.fill( Qt::transparent );
+      }
+
+      const QFont font = data( Qt::FontRole ).value< QFont >();
+
+      const QFontMetrics fm( font );
+      const int maxTextWidth = std::max( fm.boundingRect( mMinimumLabel ).width(), fm.boundingRect( mMaximumLabel ).width() );
+      const int labelGapFromRamp = fm.boundingRect( QStringLiteral( "x" ) ).width();
+      const int extraAllowance = labelGapFromRamp * 0.4; // extra allowance to avoid text clipping on right
+      const QRect labelRect( mIconSize.width() + labelGapFromRamp, 0, maxTextWidth + extraAllowance, mIconSize.height() );
+
+      mPixmap = QPixmap( mIconSize.width() + maxTextWidth + labelGapFromRamp + extraAllowance, mIconSize.height() );
+      mPixmap.fill( Qt::transparent );
+
+      QPainter p( &mPixmap );
+      p.drawPixmap( 0, 0, pix );
+      p.setFont( font );
+
+      p.drawText( labelRect, Qt::AlignTop | Qt::AlignLeft, mMaximumLabel );
+      p.drawText( labelRect, Qt::AlignBottom | Qt::AlignLeft, mMinimumLabel );
+      p.end();
+    }
+    return mPixmap;
+  }
+  else if ( role == QgsLayerTreeModelLegendNode::NodeTypeRole )
+  {
+    return QgsLayerTreeModelLegendNode::ColorRampLegend;
+  }
+
+  return QVariant();
+}
+
+QSizeF QgsColorRampLegendNode::drawSymbol( const QgsLegendSettings &settings, ItemContext *ctx, double ) const
+{
+  if ( !mRamp )
+  {
+    return QSizeF();
+  }
+
+  // setup temporary render context
+  QgsRenderContext *context = nullptr;
+  std::unique_ptr< QgsRenderContext > tempRenderContext;
+  if ( ctx && ctx->context )
+    context = ctx->context;
+  else
+  {
+    tempRenderContext = qgis::make_unique< QgsRenderContext >();
+    // QGIS 4.0 - make ItemContext compulsory, so we don't have to construct temporary render contexts here
+    Q_NOWARN_DEPRECATED_PUSH
+    tempRenderContext->setScaleFactor( settings.dpi() / 25.4 );
+    tempRenderContext->setRendererScale( settings.mapScale() );
+    tempRenderContext->setFlag( QgsRenderContext::Antialiasing, true );
+    tempRenderContext->setMapToPixel( QgsMapToPixel( 1 / ( settings.mmPerMapUnit() * tempRenderContext->scaleFactor() ) ) );
+    Q_NOWARN_DEPRECATED_POP
+    tempRenderContext->setForceVectorOutput( true );
+    tempRenderContext->setPainter( ctx ? ctx->painter : nullptr );
+
+    // setup a minimal expression context
+    QgsExpressionContext expContext;
+    expContext.appendScopes( QgsExpressionContextUtils::globalProjectLayerScopes( nullptr ) );
+    tempRenderContext->setExpressionContext( expContext );
+    context = tempRenderContext.get();
+  }
+
+  QFont symbolLabelFont = settings.style( QgsLegendStyle::SymbolLabel ).font();
+  QgsTextFormat format = QgsTextFormat::fromQFont( symbolLabelFont );
+  format.setColor( settings.fontColor() );
+
+  double minHeightMm = QgsTextRenderer::textHeight( *context, format, QStringList() << mMinimumLabel << mMaximumLabel, QgsTextRenderer::Rect ) / context->scaleFactor();
+
+  const double height = ctx && ctx->patchSize.height() > 0 ? std::max( minHeightMm / 2, ctx->patchSize.height() ) : std::max( minHeightMm, settings.symbolSize().height() );
+  const double width = ctx && ctx->patchSize.width() > 0 ? ctx->patchSize.width() : settings.symbolSize().width();
+
+  if ( ctx && ctx->painter )
+  {
+    double currentYCoord = ctx->top;
+    QPainter *p = ctx->painter;
+
+    //setup painter scaling to dots so that raster symbology is drawn to scale
+    double dotsPerMM = context->scaleFactor();
+
+    double opacity = 1;
+    if ( QgsMapLayer *layer = layerNode()->layer() )
+      opacity = layer->opacity();
+
+    QgsScopedQPainterState painterState( p );
+    context->setPainterFlagsUsingContext( p );
+
+    double rampLeftMm = 0;
+    double rampTopMm = currentYCoord;
+    switch ( settings.symbolAlignment() )
+    {
+      case Qt::AlignLeft:
+      default:
+        rampLeftMm = ctx->columnLeft;
+        break;
+
+      case Qt::AlignRight:
+        rampLeftMm = ctx->columnRight - width;
+        break;
+    }
+
+    p->scale( 1.0 / dotsPerMM, 1.0 / dotsPerMM );
+
+    QLinearGradient gradient( 0, rampTopMm * dotsPerMM, 0, rampTopMm * dotsPerMM + height * dotsPerMM );
+    if ( mRamp->type() == QgsGradientColorRamp::typeString() || mRamp->type() == QgsCptCityColorRamp::typeString() )
+    {
+      //color ramp gradient
+      QgsGradientColorRamp *gradRamp = static_cast<QgsGradientColorRamp *>( mRamp.get() );
+      gradRamp->addStopsToGradient( &gradient, opacity );
+    }
+
+    if ( settings.drawRasterStroke() )
+    {
+      QPen pen;
+      pen.setColor( settings.rasterStrokeColor() );
+      pen.setWidthF( settings.rasterStrokeWidth() * dotsPerMM );
+      pen.setJoinStyle( Qt::MiterJoin );
+      ctx->painter->setPen( pen );
+    }
+    else
+    {
+      ctx->painter->setPen( Qt::NoPen );
+    }
+
+    p->setBrush( QBrush( gradient ) );
+    p->drawRect( rampLeftMm * dotsPerMM, rampTopMm * dotsPerMM, width * dotsPerMM, height * dotsPerMM );
+
+    double labelXMin = 0;
+    double labelXMax = 0;
+    switch ( settings.symbolAlignment() )
+    {
+      case Qt::AlignLeft:
+      default:
+        labelXMin = ctx->columnLeft + std::max( width, ctx->maxSiblingSymbolWidth )
+                    + settings.style( QgsLegendStyle::Symbol ).margin( QgsLegendStyle::Right )
+                    + settings.style( QgsLegendStyle::SymbolLabel ).margin( QgsLegendStyle::Left );
+        labelXMax = ctx->columnRight;
+        break;
+
+      case Qt::AlignRight:
+        labelXMin = ctx->columnLeft;
+        // NOTE -- while the below calculations use the flipped margins from the style, that's only done because
+        // those are the only margins we expose and use for now! (and we expose them as generic margins, not side-specific
+        // ones) TODO when/if we expose other margin settings, these should be reversed...
+        labelXMax = ctx->columnRight - std::max( width, ctx->maxSiblingSymbolWidth )
+                    - settings.style( QgsLegendStyle::Symbol ).margin( QgsLegendStyle::Right )
+                    - settings.style( QgsLegendStyle::SymbolLabel ).margin( QgsLegendStyle::Left );
+        break;
+    }
+
+    const QRectF textRect( labelXMin * dotsPerMM, currentYCoord * dotsPerMM, ( labelXMax - labelXMin ) * dotsPerMM, height * dotsPerMM );
+    QgsTextRenderer::drawText( textRect, 0, QgsTextRenderer::convertQtHAlignment( settings.style( QgsLegendStyle::SymbolLabel ).alignment() ), QStringList() << mMaximumLabel, *context, format, true, QgsTextRenderer::AlignTop );
+    QgsTextRenderer::drawText( textRect, 0, QgsTextRenderer::convertQtHAlignment( settings.style( QgsLegendStyle::SymbolLabel ).alignment() ), QStringList() << mMinimumLabel, *context, format, true, QgsTextRenderer::AlignBottom );
+  }
+
+  return QSizeF( width, height );
+}
+
+