Extra tweaks to legend column auto breaking when manual breaks are present

src/core/qgslegendrenderer.cpp

@@ -439,6 +439,7 @@ int QgsLegendRenderer::setColumns( QList<LegendComponentGroup> &componentGroups
   // the target number of columns allowed is dictated by the number of forced column
   // breaks OR the manually set column count (whichever is greater!)
   const int targetNumberColumns = std::max( forcedColumnBreaks + 1, mSettings.columnCount() );
+  const int numberAutoPlacedBreaks = targetNumberColumns - forcedColumnBreaks - 1;
 
   // We know height of each group and we have to split them into columns
   // minimizing max column height. It is sort of bin packing problem, NP-hard.
@@ -450,11 +451,12 @@ int QgsLegendRenderer::setColumns( QList<LegendComponentGroup> &componentGroups
   int currentColumnGroupCount = 0; // number of groups in current column
   double currentColumnHeight = 0;
   double closedColumnsHeight = 0;
+  int autoPlacedBreaks = 0;
 
   for ( int i = 0; i < componentGroups.size(); i++ )
   {
     // Recalc average height for remaining columns including current
-    double avgColumnHeight = ( totalHeight - closedColumnsHeight ) / ( targetNumberColumns - currentColumn );
+    double avgColumnHeight = ( totalHeight - closedColumnsHeight ) / ( numberAutoPlacedBreaks + 1 - autoPlacedBreaks );
 
     LegendComponentGroup group = componentGroups.at( i );
     double currentHeight = currentColumnHeight;
@@ -463,7 +465,8 @@ int QgsLegendRenderer::setColumns( QList<LegendComponentGroup> &componentGroups
     currentHeight += group.size.height();
 
     bool canCreateNewColumn = ( currentColumnGroupCount > 0 )  // do not leave empty column
-                              && ( currentColumn < targetNumberColumns - 1 ); // must not exceed max number of columns
+                              && ( currentColumn < targetNumberColumns - 1 ) // must not exceed max number of columns
+                              && ( autoPlacedBreaks < numberAutoPlacedBreaks );
 
     bool shouldCreateNewColumn = ( currentHeight - avgColumnHeight ) > group.size.height() / 2  // center of current group is over average height
                                  && currentColumnGroupCount > 0 // do not leave empty column
@@ -481,6 +484,8 @@ int QgsLegendRenderer::setColumns( QList<LegendComponentGroup> &componentGroups
     {
       // New column
       currentColumn++;
+      if ( !group.placeColumnBreakBeforeGroup )
+        autoPlacedBreaks++;
       currentColumnGroupCount = 0;
       closedColumnsHeight += currentColumnHeight;
       currentColumnHeight = group.size.height();

tests/src/core/testqgslegendrenderer.cpp

@@ -164,6 +164,8 @@ class TestQgsLegendRenderer : public QObject
     void testColumnBreaks();
     void testColumnBreaks2();
     void testColumnBreaks3();
+    void testColumnBreaks4();
+    void testColumnBreaks5();
     void testRasterStroke();
     void testFilterByPolygon();
     void testFilterByExpression();
@@ -985,6 +987,50 @@ void TestQgsLegendRenderer::testColumnBreaks3()
   QVERIFY( _verifyImage( testName, mReport ) );
 }
 
+void TestQgsLegendRenderer::testColumnBreaks4()
+{
+  QString testName = QStringLiteral( "legend_column_breaks4" );
+
+  QgsLayerTreeModel legendModel( mRoot );
+
+  QgsLayerTreeLayer *layer = legendModel.rootGroup()->findLayer( mVL3 );
+  QgsMapLayerLegendUtils::setLegendNodeColumnBreak( layer, 0, true );
+  legendModel.refreshLayerLegend( layer );
+
+  layer = legendModel.rootGroup()->findLayer( mRL );
+  QgsMapLayerLegendUtils::setLegendNodeColumnBreak( layer, 0, true );
+  legendModel.refreshLayerLegend( layer );
+
+  QgsLegendSettings settings;
+  settings.setColumnCount( 5 );
+  settings.setSplitLayer( true );
+  _setStandardTestFont( settings, QStringLiteral( "Bold" ) );
+  _renderLegend( testName, &legendModel, settings );
+  QVERIFY( _verifyImage( testName, mReport ) );
+}
+
+void TestQgsLegendRenderer::testColumnBreaks5()
+{
+  QString testName = QStringLiteral( "legend_column_breaks5" );
+
+  QgsLayerTreeModel legendModel( mRoot );
+
+  QgsLayerTreeLayer *layer = legendModel.rootGroup()->findLayer( mVL3 );
+  QgsMapLayerLegendUtils::setLegendNodeColumnBreak( layer, 0, true );
+  legendModel.refreshLayerLegend( layer );
+
+  layer = legendModel.rootGroup()->findLayer( mRL );
+  QgsMapLayerLegendUtils::setLegendNodeColumnBreak( layer, 0, true );
+  legendModel.refreshLayerLegend( layer );
+
+  QgsLegendSettings settings;
+  settings.setColumnCount( 4 );
+  settings.setSplitLayer( false );
+  _setStandardTestFont( settings, QStringLiteral( "Bold" ) );
+  _renderLegend( testName, &legendModel, settings );
+  QVERIFY( _verifyImage( testName, mReport ) );
+}
+
 void TestQgsLegendRenderer::testRasterStroke()
 {
   QString testName = QStringLiteral( "legend_raster_border" );