1 files changed, 103 insertions, 0 deletions
diff --git a/glyph.cpp b/glyph.cpp
new file mode 100644
index 0000000..f143ee8
--- /dev/null
+++ b/glyph.cpp
@@ -0,0 +1,103 @@
+#include "glyph.h"
+
+#include <cmath>
+#include <QSGGeometry>
+#include <QSGGeometryNode>
+#include <QSGMaterial>
+#include <QSGFlatColorMaterial>
+
+const float PI = 3.1415f;
+
+Glyph::Glyph(QQuickItem *parent)
+    : QQuickItem(parent)
+    , m_size(0)
+{
+    setFlag(QQuickItem::ItemHasContents);
+}
+
+void Glyph::setSize(qreal size)
+{
+    if (size == m_size)
+        return;
+
+    m_size = size;
+    setWidth(size);
+    setHeight(size);
+    emit sizeChanged();
+    update();
+}
+
+void Glyph::setColor(const QColor &color)
+{
+    if (color == m_color)
+        return;
+
+    m_color = color;
+    emit colorChanged();
+    update();
+}
+
+int calculateCircleVertexCount(qreal radius)
+{
+    // 10 * sqrt(r) \approx 2*pi / acos(1 - 1 / (4*r))
+    return (int) (10.0 * sqrt(radius));
+}
+
+void updateCircleGeometry(QSGGeometry *geometry, const QRectF &bounds)
+{
+    int vertexCount = geometry->vertexCount();
+    float cy = bounds.center().x();
+    float cx = bounds.center().y();
+
+    float theta = 2 * PI / float(vertexCount);
+    float c = cosf(theta);
+    float s = sinf(theta);
+    float x = bounds.width() / 2;
+    float y = 0;
+
+    QSGGeometry::Point2D *vertexData = geometry->vertexDataAsPoint2D();
+    for (int i = 0; i < vertexCount; i++) {
+        vertexData[i].set(x + cx, y + cy);
+
+        float t = x;
+        x = c*x - s*y;
+        y = s*t + c*y;
+    }
+}
+
+QSGNode *Glyph::updatePaintNode(QSGNode *oldNode, UpdatePaintNodeData *)
+{
+    QSGGeometryNode *node = 0;
+    QSGGeometry *geometry = 0;
+    QSGFlatColorMaterial *material = 0;
+    int vertexCount = calculateCircleVertexCount(m_size / 2);
+
+    if (!oldNode) {
+        node = new QSGGeometryNode;
+
+        geometry = new QSGGeometry(QSGGeometry::defaultAttributes_Point2D(), vertexCount);
+        geometry->setDrawingMode(GL_POLYGON);
+        node->setGeometry(geometry);
+        node->setFlag(QSGNode::OwnsGeometry);
+
+        material = new QSGFlatColorMaterial;
+        material->setColor(m_color);
+        node->setMaterial(material);
+        node->setFlag(QSGNode::OwnsMaterial);
+    } else {
+        node = static_cast<QSGGeometryNode *>(oldNode);
+        geometry = node->geometry();
+        geometry->allocate(vertexCount);
+    }
+
+    updateCircleGeometry(geometry, boundingRect());
+    node->markDirty(QSGNode::DirtyGeometry);
+
+    material = static_cast<QSGFlatColorMaterial *>(node->material());
+    if (material->color() != m_color) {
+        material->setColor(m_color);
+        node->markDirty(QSGNode::DirtyMaterial);
+    }
+
+    return node;
+}