Stacked or grouped bars and plot legend

Two new options added to the context menu of the plot:

- Stacked bars: switches between stacked bars or grouped bars. The former
overlapped layout is avoided since it doesn't make much sense.

- Show legend: toggles the display of a plot legend with a translucent
background. Possible future improvement is dragging the legend with the
mouse.

src/PlotDock.cpp

@@ -9,7 +9,9 @@ PlotDock::PlotDock(QWidget* parent)
     : QDialog(parent),
       ui(new Ui::PlotDock),
       m_currentPlotModel(nullptr),
-      m_currentTableSettings(nullptr)
+      m_currentTableSettings(nullptr),
+      m_showLegend(false),
+      m_stackedBars(false)
 {
     ui->setupUi(this);
 
@@ -50,6 +52,18 @@ PlotDock::PlotDock(QWidget* parent)
        copy();
     });
 
+    QAction* showLegendAction = new QAction(tr("Show legend"), m_contextMenu);
+    showLegendAction->setCheckable(true);
+    m_contextMenu->addAction(showLegendAction);
+
+    connect(showLegendAction, SIGNAL(toggled(bool)), this, SLOT(toggleLegendVisible(bool)));
+
+    QAction* stackedBarsAction = new QAction(tr("Stacked bars"), m_contextMenu);
+    stackedBarsAction->setCheckable(true);
+    m_contextMenu->addAction(stackedBarsAction);
+
+    connect(stackedBarsAction, SIGNAL(toggled(bool)), this, SLOT(toggleStackedBars(bool)));
+
     connect(ui->plotWidget, &QTableView::customContextMenuRequested,
             [=](const QPoint& pos) {
         // Show menu
@@ -225,6 +239,8 @@ void PlotDock::updatePlot(SqliteTableModel* model, BrowseDataTableSettings* sett
         int x = xitem->data(PlotColumnField, Qt::UserRole).toInt();
         int xtype = xitem->data(PlotColumnType, Qt::UserRole).toInt();
 
+        ui->plotWidget->xAxis->setTickLabelRotation(0);
+
         // check if we have a x axis with datetime data
         switch (xtype) {
         case QVariant::Date: {
@@ -247,6 +263,8 @@ void PlotDock::updatePlot(SqliteTableModel* model, BrowseDataTableSettings* sett
             break;
         }
         case QVariant::String: {
+            // Ticker is set when we have got the labels
+            ui->plotWidget->xAxis->setTickLabelRotation(60);
             break;
         }
         default: {
@@ -334,6 +352,7 @@ void PlotDock::updatePlot(SqliteTableModel* model, BrowseDataTableSettings* sett
                 QCPScatterStyle scatterStyle = QCPScatterStyle(static_cast<QCPScatterStyle::ScatterShape>(shapeIdx), 5);
 
                 QCPAbstractPlottable* plottable;
+                // When the X type is String, we draw a bar chart.
                 // When it is already sorted by x, we draw a graph.
                 // When it is not sorted by x, we draw a curve, so the order selected by the user in the table or in the query is
                 // respected.  In this case the line will have loops and only None and Line is supported as line style.
@@ -342,38 +361,39 @@ void PlotDock::updatePlot(SqliteTableModel* model, BrowseDataTableSettings* sett
                     QCPBars* bars = new QCPBars(ui->plotWidget->xAxis, ui->plotWidget->yAxis);
                     plottable = bars;
                     bars->setData(xdata, ydata);
-                    QColor brush = item->backgroundColor(PlotColumnY);
-                    if (ui->plotWidget->plottableCount() > 1)
-                        brush.setAlpha(124);
-                    bars->setBrush(brush);
-                    QSharedPointer<QCPAxisTickerText> ticker(new QCPAxisTickerText);
-                    ticker->addTicks(xdata, labels);
-                    ui->plotWidget->xAxis->setTicker(ticker);
-                    ui->plotWidget->xAxis->setTickLabelRotation(60);
-                } else if (isSorted) {
-                    QCPGraph* graph = ui->plotWidget->addGraph();
-                    plottable = graph;
-                    graph->setData(xdata, ydata, /*alreadySorted*/ true);
-                    // set some graph styles not supported by the abstract plottable
-                    graph->setLineStyle((QCPGraph::LineStyle) ui->comboLineType->currentIndex());
-                    graph->setScatterStyle(scatterStyle);
-                    ui->plotWidget->xAxis->setTickLabelRotation(0);
-
+                    // Set ticker once
+                    if (ui->plotWidget->plottableCount() == 1) {
+                        QSharedPointer<QCPAxisTickerText> ticker(new QCPAxisTickerText);
+                        ticker->addTicks(xdata, labels);
+                        ui->plotWidget->xAxis->setTicker(ticker);
+                    }
+                    QColor color = item->backgroundColor(PlotColumnY);
+                    bars->setBrush(color);
+                    plottable->setPen(QPen(color.darker(150)));
                 } else {
-                    QCPCurve* curve = new QCPCurve(ui->plotWidget->xAxis, ui->plotWidget->yAxis);
-                    plottable = curve;
-                    curve->setData(tdata, xdata, ydata, /*alreadySorted*/ true);
-                    // set some curve styles not supported by the abstract plottable
-                    if (ui->comboLineType->currentIndex() == QCPCurve::lsNone)
-                        curve->setLineStyle(QCPCurve::lsNone);
-                    else
-                        curve->setLineStyle(QCPCurve::lsLine);
-                    curve->setScatterStyle(scatterStyle);
-                    ui->plotWidget->xAxis->setTickLabelRotation(0);
+                    if (isSorted) {
+                        QCPGraph* graph = ui->plotWidget->addGraph();
+                        plottable = graph;
+                        graph->setData(xdata, ydata, /*alreadySorted*/ true);
+                        // set some graph styles not supported by the abstract plottable
+                        graph->setLineStyle((QCPGraph::LineStyle) ui->comboLineType->currentIndex());
+                        graph->setScatterStyle(scatterStyle);
+                    } else {
+                        QCPCurve* curve = new QCPCurve(ui->plotWidget->xAxis, ui->plotWidget->yAxis);
+                        plottable = curve;
+                        curve->setData(tdata, xdata, ydata, /*alreadySorted*/ true);
+                        // set some curve styles not supported by the abstract plottable
+                        if (ui->comboLineType->currentIndex() == QCPCurve::lsNone)
+                            curve->setLineStyle(QCPCurve::lsNone);
+                        else
+                            curve->setLineStyle(QCPCurve::lsLine);
+                        curve->setScatterStyle(scatterStyle);
+                    }
+                    plottable->setPen(QPen(item->backgroundColor(PlotColumnY)));
                 }
 
-                plottable->setPen(QPen(item->backgroundColor(PlotColumnY)));
                 plottable->setSelectable(QCP::stDataRange);
+                plottable->setName(item->text(PlotColumnField));
 
                 // gather Y label column names
                 if(column == RowNumId)
@@ -384,6 +404,9 @@ void PlotDock::updatePlot(SqliteTableModel* model, BrowseDataTableSettings* sett
         }
 
         ui->plotWidget->rescaleAxes(true);
+        ui->plotWidget->legend->setVisible(m_showLegend);
+        // Legend with slightly transparent background brush:
+        ui->plotWidget->legend->setBrush(QColor(255, 255, 255, 150));
 
         // set axis labels
         if(x == RowNumId)
@@ -392,6 +415,8 @@ void PlotDock::updatePlot(SqliteTableModel* model, BrowseDataTableSettings* sett
             ui->plotWidget->xAxis->setLabel(model->headerData(x, Qt::Horizontal).toString());
         ui->plotWidget->yAxis->setLabel(yAxisLabels.join("|"));
     }
+
+    adjustBars();
     ui->plotWidget->replot();
 
     // Warn user if not all data has been fetched and hint about the button for loading all the data
@@ -789,3 +814,47 @@ void PlotDock::copy()
 {
     QApplication::clipboard()->setPixmap(ui->plotWidget->toPixmap());
 }
+
+void PlotDock::toggleLegendVisible(bool visible)
+{
+    m_showLegend = visible;
+    ui->plotWidget->legend->setVisible(m_showLegend);
+    ui->plotWidget->replot();
+}
+
+// Stack or group bars and set the appropiate bar width (since it is not automatically done by QCustomPlot).
+void PlotDock::adjustBars()
+{
+    const double padding = 0.15;
+    const double groupedWidth = ui->plotWidget->plottableCount()? 1.0 / ui->plotWidget->plottableCount() : 0.0;
+    QCPBars* previousBar = nullptr;
+    QCPBarsGroup* barsGroup = m_stackedBars? nullptr : new QCPBarsGroup(ui->plotWidget);
+    for (int i = 0, ie = ui->plotWidget->plottableCount(); i < ie; ++i)
+    {
+        QCPBars* bar = qobject_cast<QCPBars*>(ui->plotWidget->plottable(i));
+        if (bar) {
+            if (m_stackedBars) {
+                // Ungroup if grouped
+                bar->setBarsGroup(nullptr);
+                if (previousBar)
+                    bar->moveAbove(previousBar);
+                // Set width to ocuppy the full coordinate space, less padding
+                bar->setWidth(1.0 - padding);
+            } else {
+                // Unstack if stacked
+                bar->moveAbove(nullptr);
+                bar->setBarsGroup(barsGroup);
+                // Set width to a plot coordinate width, less padding
+                bar->setWidth(groupedWidth - padding);
+            }
+            previousBar = bar;
+        }
+    }
+}
+
+void PlotDock::toggleStackedBars(bool stacked)
+{
+    m_stackedBars = stacked;
+    adjustBars();
+    ui->plotWidget->replot();
+}

src/PlotDock.h

@@ -85,6 +85,8 @@ private:
     SqliteTableModel* m_currentPlotModel;
     BrowseDataTableSettings* m_currentTableSettings;
     QMenu* m_contextMenu;
+    bool m_showLegend;
+    bool m_stackedBars;
 
     /*!
      * \brief guessdatatype try to parse the first 10 rows and decide the datatype
@@ -93,6 +95,7 @@ private:
      * \return the guessed datatype
      */
     QVariant::Type guessDataType(SqliteTableModel* model, int column);
+    void adjustBars();
 
 private slots:
     void on_treePlotColumns_itemChanged(QTreeWidgetItem* item, int column);
@@ -104,7 +107,8 @@ private slots:
     void mousePress();
     void mouseWheel();
     void copy();
-
+    void toggleLegendVisible(bool visible);
+    void toggleStackedBars(bool stacked);
 };
 
 #endif