[FEATURE][layouts] Add "hollow" scalebar style

This matches the "hollow" scalebar style from ArcMap, and is a style used in South African mapping standards Fixes #20390 Sponsored by SLYR
qgis · Mar 22, 2020 · 1887846 · 1887846
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diff --git a/python/core/auto_generated/layout/qgslayoutitemscalebar.sip.in b/python/core/auto_generated/layout/qgslayoutitemscalebar.sip.in
@@ -615,6 +615,15 @@ Sets the cap ``style`` used when drawing the lines in the scalebar.
 Applies the default scalebar settings to the scale bar.
 
 .. seealso:: :py:func:`applyDefaultSize`
+%End
+
+    bool applyDefaultRendererSettings( QgsScaleBarRenderer *renderer );
+%Docstring
+Applies any default settings relating to the specified ``renderer`` to the item.
+
+Returns ``True`` if settings were applied.
+
+.. versionadded:: 3.14
 %End
 
     QgsUnitTypes::DistanceUnit guessUnits() const;

diff --git a/python/core/auto_generated/scalebar/qgshollowscalebarrenderer.sip.in b/python/core/auto_generated/scalebar/qgshollowscalebarrenderer.sip.in
@@ -0,0 +1,53 @@
+/************************************************************************
+ * This file has been generated automatically from                      *
+ *                                                                      *
+ * src/core/scalebar/qgshollowscalebarrenderer.h                        *
+ *                                                                      *
+ * Do not edit manually ! Edit header and run scripts/sipify.pl again   *
+ ************************************************************************/
+
+
+
+class QgsHollowScaleBarRenderer: QgsScaleBarRenderer
+{
+%Docstring
+Scalebar style that draws a single box with alternating color for the segments, with horizontal lines through
+alternating segments. AKA "South African" style.
+
+.. versionadded:: 3.14
+%End
+
+%TypeHeaderCode
+#include "qgshollowscalebarrenderer.h"
+%End
+  public:
+
+    QgsHollowScaleBarRenderer();
+%Docstring
+Constructor for QgsHollowScaleBarRenderer.
+%End
+
+    virtual QString id() const;
+
+    virtual QString visibleName() const;
+
+    virtual int sortKey() const;
+
+    virtual QgsHollowScaleBarRenderer *clone() const /Factory/;
+
+
+     virtual void draw( QgsRenderContext &context,
+               const QgsScaleBarSettings &settings,
+               const QgsScaleBarRenderer::ScaleBarContext &scaleContext ) const;
+    virtual bool applyDefaultSettings( QgsScaleBarSettings &settings ) const;
+
+
+};
+
+/************************************************************************
+ * This file has been generated automatically from                      *
+ *                                                                      *
+ * src/core/scalebar/qgshollowscalebarrenderer.h                        *
+ *                                                                      *
+ * Do not edit manually ! Edit header and run scripts/sipify.pl again   *
+ ************************************************************************/
diff --git a/python/core/auto_generated/scalebar/qgsscalebarrenderer.sip.in b/python/core/auto_generated/scalebar/qgsscalebarrenderer.sip.in
@@ -98,6 +98,15 @@ Calculates the required box size (in millimeters) for a scalebar using the speci
 %Docstring
 Calculates the required box size (in millimeters) for a scalebar using the specified ``settings`` and ``scaleContext``.
 
+.. versionadded:: 3.14
+%End
+
+    virtual bool applyDefaultSettings( QgsScaleBarSettings &settings ) const;
+%Docstring
+Applies any default settings relating to the scalebar to the passed ``settings`` object.
+
+Returns ``True`` if settings were applied.
+
 .. versionadded:: 3.14
 %End
 

diff --git a/python/core/core_auto.sip b/python/core/core_auto.sip
@@ -486,6 +486,7 @@
 %Include auto_generated/raster/qgssinglebandgrayrenderer.sip
 %Include auto_generated/raster/qgssinglebandpseudocolorrenderer.sip
 %Include auto_generated/scalebar/qgsdoubleboxscalebarrenderer.sip
+%Include auto_generated/scalebar/qgshollowscalebarrenderer.sip
 %Include auto_generated/scalebar/qgsnumericscalebarrenderer.sip
 %Include auto_generated/scalebar/qgsscalebarrenderer.sip
 %Include auto_generated/scalebar/qgsscalebarrendererregistry.sip

diff --git a/src/core/CMakeLists.txt b/src/core/CMakeLists.txt
@@ -181,6 +181,7 @@ SET(QGIS_CORE_SRCS
   providers/ogr/qgsogrtransaction.cpp
 
   scalebar/qgsdoubleboxscalebarrenderer.cpp
+  scalebar/qgshollowscalebarrenderer.cpp
   scalebar/qgsnumericscalebarrenderer.cpp
   scalebar/qgsscalebarrenderer.cpp
   scalebar/qgsscalebarrendererregistry.cpp
@@ -1272,6 +1273,7 @@ SET(QGIS_CORE_HDRS
   raster/qgssinglebandpseudocolorrenderer.h
 
   scalebar/qgsdoubleboxscalebarrenderer.h
+  scalebar/qgshollowscalebarrenderer.h
   scalebar/qgsnumericscalebarrenderer.h
   scalebar/qgsscalebarrenderer.h
   scalebar/qgsscalebarrendererregistry.h

diff --git a/src/core/layout/qgslayoutitemscalebar.cpp b/src/core/layout/qgslayoutitemscalebar.cpp
@@ -469,6 +469,11 @@ void QgsLayoutItemScaleBar::applyDefaultSettings()
   emit changed();
 }
 
+bool QgsLayoutItemScaleBar::applyDefaultRendererSettings( QgsScaleBarRenderer *renderer )
+{
+  return renderer->applyDefaultSettings( mSettings );
+}
+
 QgsUnitTypes::DistanceUnit QgsLayoutItemScaleBar::guessUnits() const
 {
   if ( !mMap )

diff --git a/src/core/layout/qgslayoutitemscalebar.h b/src/core/layout/qgslayoutitemscalebar.h
@@ -498,6 +498,15 @@ class CORE_EXPORT QgsLayoutItemScaleBar: public QgsLayoutItem
      */
     void applyDefaultSettings();
 
+    /**
+     * Applies any default settings relating to the specified \a renderer to the item.
+     *
+     * Returns TRUE if settings were applied.
+     *
+     * \since QGIS 3.14
+     */
+    bool applyDefaultRendererSettings( QgsScaleBarRenderer *renderer );
+
     /**
      * Attempts to guess the most reasonable unit choice for the scalebar, given
      * the current linked map's scale.

diff --git a/src/core/scalebar/qgshollowscalebarrenderer.cpp b/src/core/scalebar/qgshollowscalebarrenderer.cpp
@@ -0,0 +1,183 @@
+/***************************************************************************
+                            qgshollowscalebarrenderer.cpp
+                            --------------------------------
+    begin                : March 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 "qgshollowscalebarrenderer.h"
+#include "qgsscalebarsettings.h"
+#include "qgslayoututils.h"
+#include "qgssymbol.h"
+#include "qgsfillsymbollayer.h"
+#include <QList>
+#include <QPainter>
+
+QString QgsHollowScaleBarRenderer::id() const
+{
+  return QStringLiteral( "hollow" );
+}
+
+QString QgsHollowScaleBarRenderer::visibleName() const
+{
+  return QObject::tr( "Hollow" );
+}
+
+int QgsHollowScaleBarRenderer::sortKey() const
+{
+  return 8;
+}
+
+QgsHollowScaleBarRenderer *QgsHollowScaleBarRenderer::clone() const
+{
+  return new QgsHollowScaleBarRenderer( *this );
+}
+
+void QgsHollowScaleBarRenderer::draw( QgsRenderContext &context, const QgsScaleBarSettings &settings, const ScaleBarContext &scaleContext ) const
+{
+  if ( !context.painter() )
+  {
+    return;
+  }
+  QPainter *painter = context.painter();
+
+  const double scaledLabelBarSpace = context.convertToPainterUnits( settings.labelBarSpace(), QgsUnitTypes::RenderMillimeters );
+  const double scaledBoxContentSpace = context.convertToPainterUnits( settings.boxContentSpace(), QgsUnitTypes::RenderMillimeters );
+  const QFontMetricsF fontMetrics = QgsTextRenderer::fontMetrics( context, settings.textFormat() );
+  const double barTopPosition = scaledBoxContentSpace + ( settings.labelVerticalPlacement() == QgsScaleBarSettings::LabelAboveSegment ? fontMetrics.ascent() + scaledLabelBarSpace : 0 );
+  const double barHeight = context.convertToPainterUnits( settings.height(), QgsUnitTypes::RenderMillimeters );
+
+  painter->save();
+  if ( context.flags() & QgsRenderContext::Antialiasing )
+    painter->setRenderHint( QPainter::Antialiasing, true );
+
+  std::unique_ptr< QgsLineSymbol > lineSymbol( settings.lineSymbol()->clone() );
+  lineSymbol->startRender( context );
+
+  std::unique_ptr< QgsFillSymbol > fillSymbol1( settings.fillSymbol1()->clone() );
+  fillSymbol1->startRender( context );
+
+  std::unique_ptr< QgsFillSymbol > fillSymbol2( settings.fillSymbol2()->clone() );
+  fillSymbol2->startRender( context );
+
+  painter->setPen( Qt::NoPen );
+  painter->setBrush( Qt::NoBrush );
+
+  bool useColor = true; //alternate brush color/white
+  const double xOffset = firstLabelXOffset( settings, context, scaleContext );
+
+  const QList<double> positions = segmentPositions( context, scaleContext, settings );
+  const QList<double> widths = segmentWidths( scaleContext, settings );
+
+  // draw the fill
+  double minX = 0;
+  double maxX = 0;
+  QgsFillSymbol *currentSymbol = nullptr;
+  for ( int i = 0; i < positions.size(); ++i )
+  {
+    if ( useColor ) //alternating colors
+    {
+      currentSymbol = fillSymbol1.get();
+    }
+    else //secondary fill
+    {
+      currentSymbol = fillSymbol2.get();
+    }
+
+    const double thisX = context.convertToPainterUnits( positions.at( i ), QgsUnitTypes::RenderMillimeters ) + xOffset;
+    const double thisWidth = context.convertToPainterUnits( widths.at( i ), QgsUnitTypes::RenderMillimeters );
+
+    if ( i == 0 )
+      minX = thisX;
+    if ( i == positions.size() - 1 )
+      maxX = thisX + thisWidth;
+
+    QRectF segmentRect( thisX, barTopPosition, thisWidth, barHeight );
+    currentSymbol->renderPolygon( QPolygonF()
+                                  << segmentRect.topLeft()
+                                  << segmentRect.topRight()
+                                  << segmentRect.bottomRight()
+                                  << segmentRect.bottomLeft()
+                                  << segmentRect.topLeft(), nullptr, nullptr, context );
+    useColor = !useColor;
+  }
+
+  // and then the lines
+  // note that we do this layer-by-layer, to avoid ugliness where the lines touch the outer rect
+  for ( int layer = 0; layer < lineSymbol->symbolLayerCount(); ++layer )
+  {
+    // horizontal lines
+    bool drawLine = false;
+    for ( int i = 0; i < positions.size(); ++i )
+    {
+      drawLine = !drawLine;
+      if ( !drawLine )
+        continue;
+
+      const double lineX = context.convertToPainterUnits( positions.at( i ), QgsUnitTypes::RenderMillimeters ) + xOffset;
+      const double lineLength = context.convertToPainterUnits( widths.at( i ), QgsUnitTypes::RenderMillimeters );
+      lineSymbol->renderPolyline( QPolygonF()
+                                  << QPointF( lineX, barTopPosition + barHeight / 2.0 )
+                                  << QPointF( lineX + lineLength, barTopPosition + barHeight / 2.0 ),
+                                  nullptr, context, layer );
+    }
+
+    // vertical lines
+    for ( int i = 1; i < positions.size(); ++i )
+    {
+      const double lineX = context.convertToPainterUnits( positions.at( i ), QgsUnitTypes::RenderMillimeters ) + xOffset;
+      lineSymbol->renderPolyline( QPolygonF()
+                                  << QPointF( lineX, barTopPosition )
+                                  << QPointF( lineX, barTopPosition + barHeight ),
+                                  nullptr, context, layer );
+    }
+
+    // outside line
+    lineSymbol->renderPolyline( QPolygonF()
+                                << QPointF( minX, barTopPosition )
+                                << QPointF( maxX, barTopPosition )
+                                << QPointF( maxX, barTopPosition + barHeight )
+                                << QPointF( minX, barTopPosition + barHeight )
+                                << QPointF( minX, barTopPosition ),
+                                nullptr, context, layer );
+  }
+
+  lineSymbol->stopRender( context );
+  fillSymbol1->stopRender( context );
+  fillSymbol2->stopRender( context );
+  painter->restore();
+
+  //draw labels using the default method
+  drawDefaultLabels( context, settings, scaleContext );
+}
+
+bool QgsHollowScaleBarRenderer::applyDefaultSettings( QgsScaleBarSettings &settings ) const
+{
+  // null the fill symbols by default
+  std::unique_ptr< QgsFillSymbol > fillSymbol = qgis::make_unique< QgsFillSymbol >();
+  std::unique_ptr< QgsSimpleFillSymbolLayer > fillSymbolLayer = qgis::make_unique< QgsSimpleFillSymbolLayer >();
+  fillSymbolLayer->setColor( QColor( 0, 0, 0 ) );
+  fillSymbolLayer->setBrushStyle( Qt::NoBrush );
+  fillSymbolLayer->setStrokeStyle( Qt::NoPen );
+  fillSymbol->changeSymbolLayer( 0, fillSymbolLayer->clone() );
+  settings.setFillSymbol1( fillSymbol.release() );
+
+  fillSymbol = qgis::make_unique< QgsFillSymbol >();
+  fillSymbolLayer->setColor( QColor( 255, 255, 255 ) );
+  fillSymbol->changeSymbolLayer( 0, fillSymbolLayer.release() );
+  settings.setFillSymbol2( fillSymbol.release() );
+
+  return true;
+}
+
+
+
diff --git a/src/core/scalebar/qgshollowscalebarrenderer.h b/src/core/scalebar/qgshollowscalebarrenderer.h
@@ -0,0 +1,52 @@
+/***************************************************************************
+                            qgshollowscalebarrenderer.h
+                            ------------------------------
+    begin                : March 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.                                   *
+ *                                                                         *
+ ***************************************************************************/
+
+#ifndef QGSHOLLOWSCALEBARRENDERER_H
+#define QGSHOLLOWSCALEBARRENDERER_H
+
+#include "qgis_core.h"
+#include "qgsscalebarrenderer.h"
+#include <QString>
+
+/**
+ * \class QgsHollowScaleBarRenderer
+ * \ingroup core
+ * Scalebar style that draws a single box with alternating color for the segments, with horizontal lines through
+ * alternating segments. AKA "South African" style.
+ * \since QGIS 3.14
+ */
+class CORE_EXPORT QgsHollowScaleBarRenderer: public QgsScaleBarRenderer
+{
+  public:
+
+    /**
+     * Constructor for QgsHollowScaleBarRenderer.
+     */
+    QgsHollowScaleBarRenderer() = default;
+
+    QString id() const override;
+    QString visibleName() const override;
+    int sortKey() const override;
+    QgsHollowScaleBarRenderer *clone() const override SIP_FACTORY;
+
+    void draw( QgsRenderContext &context,
+               const QgsScaleBarSettings &settings,
+               const QgsScaleBarRenderer::ScaleBarContext &scaleContext ) const override;
+    bool applyDefaultSettings( QgsScaleBarSettings &settings ) const override;
+
+};
+
+#endif // QGSHOLLOWSCALEBARRENDERER_H
diff --git a/src/core/scalebar/qgsnumericscalebarrenderer.cpp b/src/core/scalebar/qgsnumericscalebarrenderer.cpp
@@ -33,7 +33,7 @@ QString QgsNumericScaleBarRenderer::visibleName() const
 
 int QgsNumericScaleBarRenderer::sortKey() const
 {
-  return 8;
+  return 9;
 }
 
 QgsNumericScaleBarRenderer *QgsNumericScaleBarRenderer::clone() const

diff --git a/src/core/scalebar/qgsscalebarrenderer.cpp b/src/core/scalebar/qgsscalebarrenderer.cpp
@@ -263,6 +263,11 @@ QSizeF QgsScaleBarRenderer::calculateBoxSize( QgsRenderContext &context, const Q
   return QSizeF( width, height );
 }
 
+bool QgsScaleBarRenderer::applyDefaultSettings( QgsScaleBarSettings & ) const
+{
+  return false;
+}
+
 QString QgsScaleBarRenderer::firstLabelString( const QgsScaleBarSettings &settings ) const
 {
   if ( settings.numberOfSegmentsLeft() > 0 )