1 files changed, 123 insertions, 0 deletions
diff --git a/barchart.cpp b/barchart.cpp
new file mode 100644
index 0000000..02509ae
--- /dev/null
+++ b/barchart.cpp
@@ -0,0 +1,123 @@
+#include "barchart.h"
+
+#include <algorithm>
+
+#include "geometry.h"
+#include "scale.h"
+
+static const QColor OUTLINE_COLOR(0, 0, 0);
+static const QColor BAR_COLOR(128, 128, 128);
+static const float DEFAULT_OPACITY = 0.8f;
+
+BarChart::BarChart(QQuickItem *parent)
+    : QQuickItem(parent)
+    , m_shouldUpdateBars(false)
+{
+    setClip(true);
+    setFlag(QQuickItem::ItemHasContents);
+    // setAcceptedMouseButtons(Qt::LeftButton);
+    setAcceptHoverEvents(true);
+}
+
+BarChart::~BarChart()
+{
+}
+
+void BarChart::setValues(const arma::vec &values)
+{
+    m_values = values;
+    m_shouldUpdateBars = true;
+    emit valuesChanged(values);
+}
+
+QSGNode *BarChart::newBarNode()
+{
+    // A bar node is:
+    // opacityNode [outlineGeomNode barGeomNode]
+
+    QSGGeometryNode *outlineGeomNode = new QSGGeometryNode;
+    QSGGeometry *outlineGeometry =
+        new QSGGeometry(QSGGeometry::defaultAttributes_Point2D(), 4);
+    outlineGeometry->setDrawingMode(GL_LINE_LOOP);
+    outlineGeomNode->setGeometry(outlineGeometry);
+    outlineGeomNode->setFlag(QSGNode::OwnsGeometry);
+    QSGFlatColorMaterial *material = new QSGFlatColorMaterial;
+    material->setColor(OUTLINE_COLOR);
+    outlineGeomNode->setMaterial(material);
+    outlineGeomNode->setFlag(QSGNode::OwnsMaterial);
+
+    QSGGeometryNode *barGeomNode = new QSGGeometryNode;
+    QSGGeometry *barGeometry =
+        new QSGGeometry(QSGGeometry::defaultAttributes_Point2D(), 4);
+    barGeometry->setDrawingMode(GL_POLYGON);
+    barGeomNode->setGeometry(barGeometry);
+    barGeomNode->setFlag(QSGNode::OwnsGeometry);
+    material = new QSGFlatColorMaterial;
+    material->setColor(BAR_COLOR);
+    barGeomNode->setMaterial(material);
+    barGeomNode->setFlag(QSGNode::OwnsMaterial);
+
+    QSGOpacityNode *opacityNode = new QSGOpacityNode;
+    opacityNode->setOpacity(DEFAULT_OPACITY);
+    opacityNode->appendChildNode(barGeomNode);
+    opacityNode->appendChildNode(outlineGeomNode);
+
+    return opacityNode;
+}
+
+void BarChart::updateBarNodeGeom(QSGNode *barNode, float x, float barWidth, float barHeight)
+{
+    QSGGeometryNode *outlineGeomNode =
+        static_cast<QSGGeometryNode *>(barNode->firstChild());
+    QSGGeometryNode *barGeomNode =
+        static_cast<QSGGeometryNode *>(barNode->firstChild()->nextSibling());
+
+    float y = height() - barHeight;
+    updateRectGeometry(outlineGeomNode->geometry(), x, y, barWidth, barHeight);
+    updateRectGeometry(barGeomNode->geometry(), x, y, barWidth, barHeight);
+}
+
+void BarChart::updateBars(QSGNode *root)
+{
+    QSGNode *node = root->firstChild();
+    float x = 0;
+    float barWidth = width() / m_values.n_elem;
+    LinearScale<float> heightScale(m_values.min(), m_values.max(), 0, height());
+
+    for (auto it = m_values.cbegin(); it != m_values.cend(); it++) {
+        updateBarNodeGeom(node, x, barWidth, heightScale((float) *it));
+        x += barWidth;
+        node = node->nextSibling();
+    }
+}
+
+QSGNode *BarChart::updatePaintNode(QSGNode *oldNode, UpdatePaintNodeData *)
+{
+    QSGNode *root = oldNode ? oldNode : new QSGNode;
+    if (m_shouldUpdateBars) {
+        // First, make sure we have the same number of values & bars
+        while (m_values.n_elem > root->childCount()) {
+            QSGNode *barNode = newBarNode();
+            root->appendChildNode(barNode);
+        }
+        while (m_values.n_elem < root->childCount()) {
+            // NOTE: as stated in docs, QSGNode's children are stored in a
+            // linked list. Hence, this operation should be as fast as expected
+            root->removeChildNode(root->firstChild());
+        }
+
+        // Then, update the geometry of bars to reflect the values
+        updateBars(root);
+        m_shouldUpdateBars = false;
+    }
+
+    return root;
+}
+
+void BarChart::hoverMoveEvent(QHoverEvent *event)
+{
+}
+
+void BarChart::mousePressEvent(QMouseEvent *event)
+{
+}