statistics: select multiple dives in scatter-plot by shift-clicking

Somewhat improve selection mechanics in the scatter-plot by
allowing additional selections with shift-clicking. When the
dives under the mouse are already selected, then deselect them.
This appears to be a rather common UI idiom in desktop
applications.

Signed-off-by: Berthold Stoeger <bstoeger@mail.tuwien.ac.at>

stats/barseries.cpp

@@ -406,7 +406,7 @@ void BarSeries::unhighlight()
 	highlighted = Index();
 }
 
-void BarSeries::selectItemsUnderMouse(const QPointF &pos)
+void BarSeries::selectItemsUnderMouse(const QPointF &pos, bool)
 {
 	Index index = getItemUnderMouse(pos);
 	if (index.bar < 0)

stats/barseries.h

@@ -69,7 +69,7 @@ public:
 	void updatePositions() override;
 	bool hover(QPointF pos) override;
 	void unhighlight() override;
-	void selectItemsUnderMouse(const QPointF &point) override;
+	void selectItemsUnderMouse(const QPointF &point, bool shiftPressed) override;
 
 private:
 	BarSeries(StatsView &view, StatsAxis *xAxis, StatsAxis *yAxis,

stats/boxseries.cpp

@@ -143,7 +143,7 @@ void BoxSeries::unhighlight()
 	highlighted = -1;
 }
 
-void BoxSeries::selectItemsUnderMouse(const QPointF &pos)
+void BoxSeries::selectItemsUnderMouse(const QPointF &pos, bool)
 {
 	int index = getItemUnderMouse(pos);
 	if (index < 0)

stats/boxseries.h

@@ -23,7 +23,7 @@ public:
 	void updatePositions() override;
 	bool hover(QPointF pos) override;
 	void unhighlight() override;
-	void selectItemsUnderMouse(const QPointF &point) override;
+	void selectItemsUnderMouse(const QPointF &point, bool shiftPressed) override;
 
 	// Note: this expects that all items are added with increasing pos
 	// and that no bar is inside another bar, i.e. lowerBound and upperBound

stats/pieseries.cpp

@@ -265,7 +265,7 @@ void PieSeries::unhighlight()
 	highlighted = -1;
 }
 
-void PieSeries::selectItemsUnderMouse(const QPointF &pos)
+void PieSeries::selectItemsUnderMouse(const QPointF &pos, bool)
 {
 	int index = getItemUnderMouse(pos);
 	if (index < 0)

stats/pieseries.h

@@ -28,7 +28,7 @@ public:
 	void updatePositions() override;
 	bool hover(QPointF pos) override;
 	void unhighlight() override;
-	void selectItemsUnderMouse(const QPointF &point) override;
+	void selectItemsUnderMouse(const QPointF &point, bool shiftPressed) override;
 
 	std::vector<QString> binNames();
 

stats/scatterseries.cpp

@@ -78,12 +78,39 @@ std::vector<int> ScatterSeries::getItemsUnderMouse(const QPointF &point) const
 	return res;
 }
 
-void ScatterSeries::selectItemsUnderMouse(const QPointF &point)
+void ScatterSeries::selectItemsUnderMouse(const QPointF &point, bool shiftPressed)
 {
 	std::vector<struct dive *> selected;
+	std::vector<int> indices = getItemsUnderMouse(point);
 
-	for(int idx: getItemsUnderMouse(point))
-		selected.push_back(items[idx].d);
+	if (shiftPressed) {
+		// When shift is pressed, add the items under the mouse to the selection
+		// or, if all items under the mouse are selected, remove them.
+		selected = getDiveSelection();
+		bool allSelected = std::all_of(indices.begin(), indices.end(),
+					       [this] (int idx) { return items[idx].d->selected; });
+		if (allSelected) {
+			// Remove items under cursor from selection. This could be made more efficient.
+			for (int idx: indices) {
+				auto it = std::find(selected.begin(), selected.end(), items[idx].d);
+				if (it != selected.end()) {
+					// Move last element to deselected element. If this already was
+					// the last element, this is a no-op. Then, chop off last element.
+					*it = selected.back();
+					selected.pop_back();
+				}
+			}
+		} else {
+			// Add items under cursor to selection
+			for (int idx: indices) {
+				if (std::find(selected.begin(), selected.end(), items[idx].d) == selected.end())
+					selected.push_back(items[idx].d);
+			}
+		}
+	} else {
+		for(int idx: indices)
+			selected.push_back(items[idx].d);
+	}
 
 	setSelection(selected, selected.empty() ? nullptr : selected.front());
 }

stats/scatterseries.h

@@ -27,7 +27,7 @@ public:
 
 	// Note: this expects that all items are added with increasing pos!
 	void append(dive *d, double pos, double value);
-	void selectItemsUnderMouse(const QPointF &point) override;
+	void selectItemsUnderMouse(const QPointF &point, bool shiftPressed) override;
 
 private:
 	// Get items under mouse.

stats/statsseries.h

@@ -17,7 +17,7 @@ public:
 	virtual void updatePositions() = 0;	// Called if chart geometry changes.
 	virtual bool hover(QPointF pos) = 0;	// Called on mouse movement. Return true if an item of this series is highlighted.
 	virtual void unhighlight() = 0;		// Unhighlight any highlighted item.
-	virtual void selectItemsUnderMouse(const QPointF &pos) = 0;
+	virtual void selectItemsUnderMouse(const QPointF &pos, bool shiftPressed) = 0;
 	virtual void divesSelected(const QVector<dive *> &dives);
 
 protected:

stats/statsview.cpp

@@ -81,8 +81,9 @@ void StatsView::mousePressEvent(QMouseEvent *event)
 		}
 	}
 
+	bool shiftPressed = event->modifiers() & Qt::ShiftModifier;
 	for (auto &series: series)
-		series->selectItemsUnderMouse(pos);
+		series->selectItemsUnderMouse(pos, shiftPressed);
 }
 
 void StatsView::mouseReleaseEvent(QMouseEvent *)