QCustomPlot之平滑曲线下（九）
接上篇，上篇只是实现了平滑曲线的绘制，但是并没有实现平滑曲线与0点线之间的填充区域以及两个`QCPGraph`之间的填充区域，我们将在这里实现它们
#### drawFill函数的修改
```
void QCPGraph::drawFill(QCPPainter *painter, QVector<QPointF> *lines) const
{
if (mLineStyle == lsImpulse) return; // fill doesn't make sense for impulse plot
if (painter->brush().style() == Qt::NoBrush || painter->brush().color().alpha() == 0) return;
applyFillAntialiasingHint(painter);
QVector<QCPDataRange> segments = getNonNanSegments(lines, keyAxis()->orientation());
if (!mChannelFillGraph)// 与0点线围成的区域
{
// draw base fill under graph, fill goes all the way to the zero-value-line:
for (int i=0; i<segments.size(); ++i)
if (mSmooth && mLineStyle == lsLine) painter->drawPath(getSmoothFillPath(lines, segments.at(i))); // 平滑曲线
else painter->drawPolygon(getFillPolygon(lines, segments.at(i))); // 折线
} else // 与其它QCPGraph围成的区域
{
// draw fill between this graph and mChannelFillGraph:
QVector<QPointF> otherLines;
mChannelFillGraph->getLines(&otherLines, QCPDataRange(0, mChannelFillGraph->dataCount()));
if (!otherLines.isEmpty())
{
QVector<QCPDataRange> otherSegments = getNonNanSegments(&otherLines, mChannelFillGraph->keyAxis()->orientation());
QVector<QPair<QCPDataRange, QCPDataRange> > segmentPairs = getOverlappingSegments(segments, lines, otherSegments, &otherLines);
for (int i=0; i<segmentPairs.size(); ++i) {
if (mSmooth && mLineStyle == lsLine && mChannelFillGraph->mLineStyle == lsLine) // 稍后会解释为什么要限制线风格为lsLine
painter->drawPath(getSmoothChannelFillPath(lines, segmentPairs.at(i).first, &otherLines, segmentPairs.at(i).second));// 平滑曲线
else
painter->drawPolygon(getChannelFillPolygon(lines, segmentPairs.at(i).first, &otherLines, segmentPairs.at(i).second)); // 折线
}
}
}
}
```
#### 与0点线之间的填充区域
```
const QPainterPath QCPGraph::getSmoothFillPath(const QVector<QPointF> *lineData, QCPDataRange segment) const
{
// 只有一个点构不成填充区域
if (segment.size() < 2)
return QPainterPath();
// 起点，终点对应在轴上的位置
QPointF start = getFillBasePoint(lineData->at(segment.begin()));
QPointF end = getFillBasePoint(lineData->at(segment.end() - 1));
// 将平滑曲线连成一个封闭区域
QPainterPath path = SmoothCurveGenerator::generateSmoothCurve(*lineData);
path.lineTo(end);
path.lineTo(start);
path.lineTo(lineData->at(segment.begin()));
return path;
}
```
#### 与其它QCPGraph围成的区域
`getSmoothChannelFillPath`基本是从`getChannelFillPolygon`复制过来的，我们在这上面进行修改，修改的内容我都有注释
```
const QPainterPath QCPGraph::getSmoothChannelFillPath(const QVector<QPointF> *thisData, QCPDataRange thisSegment,
const QVector<QPointF> *otherData, QCPDataRange otherSegment) const
{
QPainterPath result;
if (!mChannelFillGraph)
return result;
QCPAxis *keyAxis = mKeyAxis.data();
QCPAxis *valueAxis = mValueAxis.data();
if (!keyAxis || !valueAxis) { qDebug() << Q_FUNC_INFO << "invalid key or value axis"; return result; }
if (!mChannelFillGraph.data()->mKeyAxis) { qDebug() << Q_FUNC_INFO << "channel fill target key axis invalid"; return result; }
if (mChannelFillGraph.data()->mKeyAxis.data()->orientation() != keyAxis->orientation())
return result; // don't have same axis orientation, can't fill that (Note: if keyAxis fits, valueAxis will fit too, because it's always orthogonal to keyAxis)
if (thisData->isEmpty()) return result;
QVector<QPointF> thisSegmentData(thisSegment.size());
QVector<QPointF> otherSegmentData(otherSegment.size());
std::copy(thisData->constBegin()+thisSegment.begin(), thisData->constBegin()+thisSegment.end(), thisSegmentData.begin());
std::copy(otherData->constBegin()+otherSegment.begin(), otherData->constBegin()+otherSegment.end(), otherSegmentData.begin());
// pointers to be able to swap them, depending which data range needs cropping:
QVector<QPointF> *staticData = &thisSegmentData;
QVector<QPointF> *croppedData = &otherSegmentData;
//! 以下为添加的内容
result = SmoothCurveGenerator::generateSmoothCurve(thisSegmentData);
if (mChannelFillGraph->mSmooth && mChannelFillGraph->mLineStyle == lsLine) {// mChannelFillGraph也是平滑曲线
QVector<QPointF> otherSegmentDataReverse(otherSegmentData.size());
for (int i = otherSegmentData.size() - 1; i >= 0; --i)
otherSegmentDataReverse = otherSegmentData.at(i);
result = SmoothCurveGenerator::generateSmoothCurve(result, otherSegmentDataReverse);
} else {// mChannelFillGraph 是折线
// mLineStyle != lsLine 会导致闪烁，目前还不知道什么原因造成
for (int i = otherSegmentData.size() - 1; i >= 0; --i)
result.lineTo(otherSegmentData.at(i));
}
//!
// crop both vectors to ranges in which the keys overlap (which coord is key, depends on axisType):
if (keyAxis->orientation() == Qt::Horizontal)
{
// x is key
// crop lower bound:
if (staticData->first().x() < croppedData->first().x()) // other one must be cropped
qSwap(staticData, croppedData);
const int lowBound = findIndexBelowX(croppedData, staticData->first().x());
if (lowBound == -1) return result; // key ranges have no overlap
//! 以下为添加的内容
QPointF firstPoint = QPointF(croppedData->at(0).x(), valueAxis->coordToPixel(valueAxis->range().upper));// 注意这里只裁剪到了轴矩形的可见区域
//!
croppedData->remove(0, lowBound);
// set lowest point of cropped data to fit exactly key position of first static data point via linear interpolation:
if (croppedData->size() < 2) return result; // need at least two points for interpolation
double slope;
if (!qFuzzyCompare(croppedData->at(1).x(), croppedData->at(0).x()))
slope = (croppedData->at(1).y()-croppedData->at(0).y())/(croppedData->at(1).x()-croppedData->at(0).x());
else
slope = 0;
(*croppedData).setY(croppedData->at(0).y()+slope*(staticData->first().x()-croppedData->at(0).x()));
(*croppedData).setX(staticData->first().x());
//! 以下为添加的内容
QPointF lastPoint = QPointF(staticData->first().x(), valueAxis->coordToPixel(valueAxis->range().lower));// 注意这里只裁剪到了轴矩形的可见区域
QPainterPath droppedPath;
droppedPath.addRect(QRectF(firstPoint, lastPoint).normalized());
result -= droppedPath;// 裁掉多余区域
//!
// crop upper bound:
if (staticData->last().x() > croppedData->last().x()) // other one must be cropped
qSwap(staticData, croppedData);
int highBound = findIndexAboveX(croppedData, staticData->last().x());
if (highBound == -1) return result; // key ranges have no overlap
//! 以下为添加的内容
firstPoint = QPointF(croppedData->last().x(), valueAxis->coordToPixel(valueAxis->range().lower));// 注意这里只裁剪到了轴矩形的可见区域
//!
croppedData->remove(highBound+1, croppedData->size()-(highBound+1));
// set highest point of cropped data to fit exactly key position of last static data point via linear interpolation:
if (croppedData->size() < 2) return result; // need at least two points for interpolation
const int li = croppedData->size()-1; // last index
if (!qFuzzyCompare(croppedData->at(li).x(), croppedData->at(li-1).x()))
slope = (croppedData->at(li).y()-croppedData->at(li-1).y())/(croppedData->at(li).x()-croppedData->at(li-1).x());
else
slope = 0;
(*croppedData).setY(croppedData->at(li-1).y()+slope*(staticData->last().x()-croppedData->at(li-1).x()));
(*croppedData).setX(staticData->last().x());
//! 以下为添加的内容
lastPoint = QPointF(staticData->last().x(), valueAxis->coordToPixel(valueAxis->range().upper));
droppedPath = QPainterPath();
droppedPath.addRect(QRectF(firstPoint, lastPoint).normalized());
result -= droppedPath;// 裁掉多余区域
//!
} else // mKeyAxis->orientation() == Qt::Vertical
{
// y is key
// crop lower bound:
if (staticData->first().y() < croppedData->first().y()) // other one must be cropped
qSwap(staticData, croppedData);
int lowBound = findIndexBelowY(croppedData, staticData->first().y());
if (lowBound == -1) return result; // key ranges have no overlap
//! 以下为添加的内容
QPointF firstPoint = QPointF(valueAxis->coordToPixel(valueAxis->range().upper), croppedData->first().y());
//!
croppedData->remove(0, lowBound);
// set lowest point of cropped data to fit exactly key position of first static data point via linear interpolation:
if (croppedData->size() < 2) return result; // need at least two points for interpolation
double slope;
if (!qFuzzyCompare(croppedData->at(1).y(), croppedData->at(0).y())) // avoid division by zero in step plots
slope = (croppedData->at(1).x()-croppedData->at(0).x())/(croppedData->at(1).y()-croppedData->at(0).y());
else
slope = 0;
(*croppedData).setX(croppedData->at(0).x()+slope*(staticData->first().y()-croppedData->at(0).y()));
(*croppedData).setY(staticData->first().y());
//! 以下为添加的内容
QPointF lastPoint = QPointF(valueAxis->coordToPixel(valueAxis->range().lower), staticData->first().y());
QPainterPath droppedPath;
droppedPath.addRect(QRectF(firstPoint, lastPoint).normalized());
result -= droppedPath;
//!
// crop upper bound:
if (staticData->last().y() > croppedData->last().y()) // other one must be cropped
qSwap(staticData, croppedData);
int highBound = findIndexAboveY(croppedData, staticData->last().y());
if (highBound == -1) return result; // key ranges have no overlap
//! 以下为添加的内容
firstPoint = QPointF(valueAxis->coordToPixel(valueAxis->range().lower), croppedData->last().y());
//!
croppedData->remove(highBound+1, croppedData->size()-(highBound+1));
// set highest point of cropped data to fit exactly key position of last static data point via linear interpolation:
if (croppedData->size() < 2) return result; // need at least two points for interpolation
int li = croppedData->size()-1; // last index
if (!qFuzzyCompare(croppedData->at(li).y(), croppedData->at(li-1).y())) // avoid division by zero in step plots
slope = (croppedData->at(li).x()-croppedData->at(li-1).x())/(croppedData->at(li).y()-croppedData->at(li-1).y());
else
slope = 0;
(*croppedData).setX(croppedData->at(li-1).x()+slope*(staticData->last().y()-croppedData->at(li-1).y()));
(*croppedData).setY(staticData->last().y());
//! 以下为添加的内容
lastPoint = QPointF(valueAxis->coordToPixel(valueAxis->range().upper), staticData->last().y());
droppedPath = QPainterPath();
droppedPath.addRect(QRectF(firstPoint, lastPoint).normalized());
result -= droppedPath;
//!
}
return result;
}
```
#### 已知问题
- 限制线风格为`lsLine`的原因是因为其它风格可能会导致围成的区域在拖动/缩放的时候可能导致闪烁，而且其它风格对于平滑曲线来说并没有意义，所以干脆将风格限制为了`lsLine`
- 由于算法的原因，当点只有两个的时候，曲线会变成直线`Special case: Bezier curve should be a straight line.`
虽然有以上的问题，但已经可以满足我们的使用了
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