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// Copyright (C) 2024 Stan Morris.
// SPDX-License-Identifier: LicenseRef-Qt-Commercial OR GPL-3.0-only
#include "IndexedSpiralItem.h"
#include <QSGGeometry>
#include <QSGGeometryNode>
#include <QSGVertexColorMaterial>
#include <algorithm>
namespace {
std::array<int, 4> colorParts(const QColor &color) {
return {color.red(), color.green(), color.blue(), color.alpha()};
}
}
IndexedSpiralItem::IndexedSpiralItem()
{
setFlag(QQuickItem::ItemHasContents);
setWidth(720);
setHeight(720);
connect(this, &IndexedSpiralItem::indexCountChanged,
this, &QQuickItem::update);
}
QSGNode *IndexedSpiralItem::updatePaintNode(QSGNode *oldNode,
UpdatePaintNodeData *)
{
auto *n = static_cast<QSGGeometryNode *>(oldNode);
if (!n) {
n = new QSGGeometryNode();
configureGeometryNode(n);
} else {
if (applyIndexChange(n))
n->markDirty(QSGNode::DirtyGeometry);
}
return n;
}
// Return true if index count is changed
bool IndexedSpiralItem::applyIndexChange(QSGGeometryNode *geometryNode)
{
auto *geometry = geometryNode->geometry();
if (!geometry)
return false;
const int indexCount = geometry->indexCount();
/* When the exposed index count is less than or equal to the number
* of allocated indexes, the spiral grows outward from the middle.
*
* However when the same index count is greater than the number of
* allocated indexes, the spiral will receed from the center towards
* the outer edge.
*/
const bool willGrowFromCenter = m_indexCount <= m_maxIndices;
const int nextCount = willGrowFromCenter ? m_indexCount
: 2*m_maxIndices - m_indexCount;
const bool isDirectionChanging = willGrowFromCenter != m_growFromCenter;
if (isDirectionChanging || nextCount != indexCount) {
if (isDirectionChanging) {
auto * const indexData = geometry->indexDataAsUShort();
/* Swap direction of growth by reversing all the indices.
*
* According to value of m_growFromCenter, if:
* true - one-less-than-capacity hides last-added vertex
* which is at outer edge of spiral, and as the index
* count decreases the spiral gets smaller
* false - one-less-than-capacity hides first-added vertex
* which is in the center, and as the index count decreases
* the spiral becomes increasingly hollow
*/
std::reverse(indexData, indexData + m_maxIndices);
m_growFromCenter = willGrowFromCenter;
}
const int newCount = qBound(1,
nextCount,
m_maxIndices);
geometry->setIndexCount(newCount);
return true;
}
return false;
}
void IndexedSpiralItem::configureGeometryNode(QSGGeometryNode *geometryNode)
{
// Set the geometry on the node
auto *geometry = createGeometry();
geometryNode->setGeometry(geometry);
geometryNode->setFlag(QSGNode::OwnsGeometry);
// Set a ColoredPoint2D material
geometryNode->setMaterial(new QSGVertexColorMaterial());
geometryNode->setFlag(QSGNode::OwnsMaterial);
}
QSGGeometry *IndexedSpiralItem::createGeometry() const
{
auto *geometry = new QSGGeometry(QSGGeometry::defaultAttributes_ColoredPoint2D(),
m_maxVertices,
m_maxIndices);
geometry->setDrawingMode(QSGGeometry::DrawLineStrip);
geometry->setLineWidth(3);
// populate the geometry
configureGeometry(geometry);
configureColors(geometry);
return geometry;
}
void IndexedSpiralItem::configureGeometry(QSGGeometry *geometry) const
{
constexpr double pi = 3.14159265f;
constexpr int linesPerRing = 360; // 360 fits 60000 verts into 720x720 area
constexpr float angleIncrement = 2 * pi / linesPerRing;
constexpr float lineSeparation = 8;
constexpr float radiusIncrement = lineSeparation / linesPerRing;
float radius = 1.5f;
float xOffset = width()/2;
float yOffset = height()/2;
float angle = float(2 * pi / 1000.f);;
// Iterate through all vertices
auto *pt = geometry->vertexDataAsColoredPoint2D();
for (int i = 0; i < m_maxVertices; ++i, ++pt) {
pt->x = radius * cos(angle) + xOffset;
pt->y = radius * sin(angle) + yOffset;
radius += radiusIncrement;
// Keep angle in 2*pi radians -- makes debugging easier
angle += angleIncrement;
if (angle > 2 * M_PI)
angle = (2 * M_PI) - angle;
}
auto *indexData = geometry->indexDataAsUShort();
for (ushort i = 0; i < m_maxIndices; ++i, ++indexData) {
*indexData = i;
}
}
void IndexedSpiralItem::configureColors(QSGGeometry *geometry) const
{
const auto colors = std::array<QColor, 3> {
QColor("lime"),
QColor("magenta"),
QColor("white")
};
constexpr int segmentLength = 20;
auto *pt = geometry->vertexDataAsColoredPoint2D();
for (int i = 0; i < m_maxVertices; ++i, ++pt) {
const bool isEndOfSpiral = i <= 20*segmentLength
|| i > (m_maxVertices - segmentLength);
auto index = isEndOfSpiral ? 2 :
((i/segmentLength)%2 == 0) ? 1
: 0;
const auto [r, g, b, a] = colorParts(colors[index]);
pt->r = r;
pt->g = g;
pt->b = b;
pt->a = a;
}
}
int IndexedSpiralItem::indexCount() const
{
return m_indexCount;
}
void IndexedSpiralItem::setIndexCount(int newIndexCount)
{
if (m_indexCount == newIndexCount)
return;
m_indexCount = newIndexCount;
emit indexCountChanged();
}
int IndexedSpiralItem::maxIndices() const
{
return m_maxIndices;
}
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