参考：https://www.jianshu.com/p/9f2763469030
使用到qcustomplot，想在鼠标停在某个点时，显示该点的值。从网上找到例子，加入到工程中。
qcustomplot源码下载：https://www.qcustomplot.com/index.php/download
工程中，点击按钮调出对话框，在对话框中显示折线。
对话框类
DlgPlot1.h
#ifndef DLGPLOT1_H
#define DLGPLOT1_H
#include <QDialog>
#include "qcustomplot.h"
#include "CustomPlotTooltip.h"
namespace Ui {
class DlgPlot1;
}
class DlgPlot1 : public QDialog
{
Q_OBJECT
public:
explicit DlgPlot1(QWidget *parent = nullptr);
~DlgPlot1();
public:
private:
void setupScatterStyleDemo(QCustomPlot *customPlot);
private slots:
void on_btnRefresh_clicked();
private:
Ui::DlgPlot1 *ui;
QCPToolTip* m_pCpTip;
};
#endif // DLGPLOT1_H
DlgPlot1.cpp
1 #include "DlgPlot1.h"
2 #include "ui_DlgPlot1.h"
3 #include "CustomPlotTooltip.h"
4
5 DlgPlot1::DlgPlot1(QWidget *parent) :
6 QDialog(parent),
7 ui(new Ui::DlgPlot1)
8 {
9 ui->setupUi(this);
10 QString demoName = "Scatter Style Demo";
11 this->setWindowTitle(demoName);
12 setupScatterStyleDemo(ui->customPlot);
13
14 m_pCpTip = new QCPToolTip(ui->customPlot);
15 }
16
17 DlgPlot1::~DlgPlot1()
18 {
19 delete ui;
20 }
21
22 void DlgPlot1::on_btnRefresh_clicked()
23 {
24
25 }
26
27 void DlgPlot1::setupScatterStyleDemo(QCustomPlot *customPlot)
28 {
29 customPlot->legend->setVisible(true);
30 customPlot->legend->setFont(QFont("Helvetica", 9));
31 customPlot->legend->setRowSpacing(-3);
32 QVector<QCPScatterStyle::ScatterShape> shapes;
33 QVector<QColor> colors;
34 colors << Qt::blue;
35 colors << Qt::red;
36 colors << Qt::green;
37 // shapes << QCPScatterStyle::ssCross;
38 // shapes << QCPScatterStyle::ssPlus;
39 // shapes << QCPScatterStyle::ssCircle;
40 shapes << QCPScatterStyle::ssDisc;
41 shapes << QCPScatterStyle::ssDisc;
42 // shapes << QCPScatterStyle::ssSquare;
43 // shapes << QCPScatterStyle::ssDiamond;
44 // shapes << QCPScatterStyle::ssStar;
45 // shapes << QCPScatterStyle::ssTriangle;
46 // shapes << QCPScatterStyle::ssTriangleInverted;
47 // shapes << QCPScatterStyle::ssCrossSquare;
48 // shapes << QCPScatterStyle::ssPlusSquare;
49 // shapes << QCPScatterStyle::ssCrossCircle;
50 // shapes << QCPScatterStyle::ssPlusCircle;
51 // shapes << QCPScatterStyle::ssPeace;
52 // shapes << QCPScatterStyle::ssCustom;
53 // shapes << QCPScatterStyle::ssDot;
54
55 QPen pen;
56 // add graphs with different scatter styles:
57 for (int i=0; i<shapes.size(); ++i)
58 {
59 customPlot->addGraph();
60 pen.setColor(colors.at(i));
61 // generate data:
62 QVector<double> x, y;
63 if(i == 0){
64 x << 2005 << 2006 << 2007 << 2008 << 2009 << 2010 << 2011;
65 y << 2.17 << 3.42 << 4.94 << 10.38 << 15.86 << 29.33 << 52.1;
66 }
67 else if(i == 1){
68 x << 2005 << 2006 << 2007 << 2008 << 2009 << 2010 << 2011;
69 y << 2 << 9 << 6 << 15 << 89 << 11 << 20;
70 }
71 customPlot->graph()->setData(x, y);
72 customPlot->graph()->rescaleAxes(true);
73 customPlot->graph()->setPen(pen);
74 customPlot->graph()->setName(QCPScatterStyle::staticMetaObject.enumerator(QCPScatterStyle::staticMetaObject.indexOfEnumerator("ScatterShape")).valueToKey(shapes.at(i)));
75 customPlot->graph()->setLineStyle(QCPGraph::lsLine);
76 // set scatter style:
77 if (shapes.at(i) != QCPScatterStyle::ssCustom)
78 {
79 customPlot->graph()->setScatterStyle(QCPScatterStyle(shapes.at(i), 10));
80 }
81 else
82 {
83 QPainterPath customScatterPath;
84 for (int i=0; i<3; ++i)
85 customScatterPath.cubicTo(qCos(2*M_PI*i/3.0)*9, qSin(2*M_PI*i/3.0)*9, qCos(2*M_PI*(i+0.9)/3.0)*9, qSin(2*M_PI*(i+0.9)/3.0)*9, 0, 0);
86 customPlot->graph()->setScatterStyle(QCPScatterStyle(customScatterPath, QPen(Qt::black, 0), QColor(255, 255, 255, 50), 10));
87 }
88 }
89
90 // set blank axis lines:
91 customPlot->rescaleAxes();
92 customPlot->xAxis->setTicks(true);
93 customPlot->yAxis->setTicks(true);
94 customPlot->xAxis->setTickLabels(true);
95 customPlot->yAxis->setTickLabels(true);
96 // make top right axes clones of bottom left axes:
97 customPlot->axisRect()->setupFullAxesBox();
98 }
DlgPlot1.ui
1 <?xml version="1.0" encoding="UTF-8"?> 2 <ui version="4.0"> 3 <class>DlgPlot1</class> 4 <widget class="QDialog" name="DlgPlot1"> 5 <property name="geometry"> 6 <rect> 7 <x>0</x> 8 <y>0</y> 9 <width>400</width> 10 <height>300</height> 11 </rect> 12 </property> 13 <property name="windowTitle"> 14 <string>Dialog</string> 15 </property> 16 <layout class="QGridLayout" name="gridLayout"> 17 <item row="0" column="0" colspan="2"> 18 <widget class="QCustomPlot" name="customPlot" native="true"/> 19 </item> 20 <item row="1" column="0"> 21 <spacer name="horizontalSpacer"> 22 <property name="orientation"> 23 <enum>Qt::Horizontal</enum> 24 </property> 25 <property name="sizeHint" stdset="0"> 26 <size> 27 <width>293</width> 28 <height>20</height> 29 </size> 30 </property> 31 </spacer> 32 </item> 33 <item row="1" column="1"> 34 <widget class="QPushButton" name="btnRefresh"> 35 <property name="text"> 36 <string>刷 新</string> 37 </property> 38 </widget> 39 </item> 40 </layout> 41 </widget> 42 <customwidgets> 43 <customwidget> 44 <class>QCustomPlot</class> 45 <extends>QWidget</extends> 46 <header location="global">qcustomplot.h</header> 47 <container>1</container> 48 </customwidget> 49 </customwidgets> 50 <resources/> 51 <connections/> 52 </ui>
CustomPlotTooltip.h
1 #ifndef CUSTOMPLOTTOOLTIP_H
2 #define CUSTOMPLOTTOOLTIP_H
3 #include "qcustomplot.h"
4
5 class QCPToolTip : public QCPAbstractItem
6 {
7 Q_OBJECT
8 public:
9 explicit QCPToolTip(QCustomPlot *parentPlot);
10
11 void setText(const QString &text);
12 void setFont(const QFont &font);
13 void setTextColor(const QColor &color);
14 void setBorderPen(const QPen &pen);
15 void setBrush(const QBrush &brush);
16 void setRadius(double xRadius, double yRadius, Qt::SizeMode mode = Qt::AbsoluteSize);
17 void setOffset(double xOffset, double yOffset);
18 void setPadding(const QMargins &paddings);
19
20 Q_SLOT void handleTriggerEvent(QMouseEvent *event);
21 void updatePosition(const QPointF &newPos, bool replot = false);
22
23 void update();
24
25 virtual double selectTest(const QPointF &pos, bool onlySelectable, QVariant *details) const Q_DECL_OVERRIDE;
26
27 QCPItemPosition * const position;
28 protected:
29 bool mPlotReplot; // 表明是由QCustomPlot刷新的，需要更新位置
30 QString mText;
31 Qt::Alignment mTextAlignment;
32 QFont mFont;
33 QColor mTextColor;
34 QPen mBorderPen;
35 QBrush mBrush;
36
37 QPointF mRadius;
38 Qt::SizeMode mSizeMode;
39
40 QPointF mOffset; // 偏移鼠标的距离
41 QMargins mPadding;
42
43 QCPGraph *mHighlightGraph;
44 QPointF mGraphDataPos;
45
46 virtual void draw(QCPPainter *painter) Q_DECL_OVERRIDE;
47 virtual void drawGraphScatterPlot(QCPPainter *painter, QCPGraph *graph, const QPointF &pos);
48
49 int pickClosest(double target, const QVector<double> &vector);
50 };
51 #endif // CUSTOMPLOTTOOLTIP_H
CustomPlotTooltip.cpp
1 #include "CustomPlotTooltip.h"
2 #include <QToolTip>
3 #include <QCursor>
4
5 QCPToolTip::QCPToolTip(QCustomPlot *parentPlot)
6 : QCPAbstractItem(parentPlot),
7 position(createPosition(QLatin1String("position"))),
8 mPlotReplot(true),
9 mTextAlignment(Qt::AlignLeft | Qt::AlignVCenter),
10 mRadius(6, 6),
11 mSizeMode(Qt::AbsoluteSize),
12 mHighlightGraph(nullptr)
13 {
14 position->setType(QCPItemPosition::ptAbsolute);
15 setSelectable(false);
16 setLayer("overlay");
17
18 setBorderPen(Qt::NoPen);
19 setBrush(QColor(87, 98, 93, 180));
20 setTextColor(Qt::white);
21 setOffset(10, 0);
22 setPadding(QMargins(6, 6, 6, 6));
23 connect(mParentPlot, SIGNAL(mouseMove(QMouseEvent *)), this, SLOT(handleTriggerEvent(QMouseEvent *)));
24 }
25
26 void QCPToolTip::setText(const QString &text)
27 {
28 mText = text;
29 // QToolTip::showText(mParentPlot->cursor().pos(), text, mParentPlot);
30 }
31
32 void QCPToolTip::setFont(const QFont &font)
33 {
34 mFont = font;
35 }
36
37 void QCPToolTip::setTextColor(const QColor &color)
38 {
39 mTextColor = color;
40 }
41
42 void QCPToolTip::setBorderPen(const QPen &pen)
43 {
44 mBorderPen = pen;
45 }
46
47 void QCPToolTip::setBrush(const QBrush &brush)
48 {
49 mBrush = brush;
50 }
51
52 void QCPToolTip::setRadius(double xRadius, double yRadius, Qt::SizeMode mode)
53 {
54 mRadius.setX(xRadius);
55 mRadius.setY(yRadius);
56 mSizeMode = mode;
57 }
58
59 void QCPToolTip::setOffset(double xOffset, double yOffset)
60 {
61 mOffset.setX(xOffset);
62 mOffset.setY(yOffset);
63 }
64
65 void QCPToolTip::setPadding(const QMargins &paddings)
66 {
67 mPadding = paddings;
68 }
69
70 void QCPToolTip::handleTriggerEvent(QMouseEvent *event)
71 {
72 updatePosition(event->pos(), true); // true 表示需要单独刷新，将调用update函数
73 }
74
75 void QCPToolTip::update()
76 {
77 mPlotReplot = false; // 表明单独刷新
78 layer()->replot();
79 mPlotReplot = true; // 单独刷新完毕
80 }
81
82 // 不需要鼠标点击测试，因为ToolTip是跟随鼠标的，鼠标点击不到
83 double QCPToolTip::selectTest(const QPointF &pos, bool onlySelectable, QVariant *details) const
84 {
85 Q_UNUSED(pos)
86 Q_UNUSED(onlySelectable)
87 Q_UNUSED(details)
88 return -1;
89 }
90
91 int QCPToolTip::pickClosest(double target, const QVector<double> &vector)
92 {
93 if (vector.size() < 2)
94 return 0;
95
96 // 查找第一个大于或等于target的位置
97 auto it = std::lower_bound(vector.constBegin(), vector.constEnd(), target);
98
99 if (it == vector.constEnd()) return vector.size() - 1;
100 else if (it == vector.constBegin()) return 0;
101 else return target - *(it - 1) < *it - target ? (it - vector.constBegin() - 1): (it - vector.constBegin());
102 }
103
104 void QCPToolTip::updatePosition(const QPointF &newPos, bool replot)
105 {
106 mHighlightGraph = nullptr;
107 double tolerance = mParentPlot->selectionTolerance();
108
109 for (int i = mParentPlot->graphCount() - 1; i >= 0; --i) {
110 QCPGraph *graph = mParentPlot->graph(i);
111 if (!graph->realVisibility() || graph->scatterStyle().isNone()) // graph不可见或者scatter style 为空的时候，不显示ToolTip
112 continue;
113
114 double limitDistance = tolerance; // limitDistance 用于选择的范围
115 double penWidth = graph->pen().widthF();
116 QCPScatterStyle scatterStyle = graph->scatterStyle();
117
118 limitDistance = qMax(scatterStyle.size(), tolerance);
119 penWidth = scatterStyle.isPenDefined() ? scatterStyle.pen().widthF() : penWidth;
120
121 QVariant details;
122 double currentDistance = graph->selectTest(newPos, false, &details); // details会返回最接近的一个数据点，selectTest是不精确的，所以后面还要判断
123
124 QCPDataSelection selection = details.value<QCPDataSelection>();
125 if (currentDistance >= 0 && currentDistance < limitDistance + penWidth && !selection.isEmpty()) {
126 // 取出当前key和value值，并且转换为像素位置
127 double key = graph->dataMainKey(selection.dataRange().begin());
128 double value = graph->dataMainValue(selection.dataRange().begin());
129 QPointF pos = graph->coordsToPixels(key, value);
130
131 QRectF rect(pos.x() - limitDistance * 0.5, pos.y() - limitDistance * 0.5, limitDistance, limitDistance);
132 rect = rect.adjusted(-penWidth, -penWidth, penWidth, penWidth);
133
134 if (rect.contains(newPos)) { // 通过矩形判断，鼠标位置是否在数据点上
135 // // 解开以下注释，可以使得我们的文字跟轴标签的文字是一样的（但跟轴标签实际的显示效果可能是不一样的，这里要注意，例如对于科学计数法，轴可能会使用美化），同时要注意当轴标签不显示的时候tickVectorLabels返回的是空的，所以我们要做一下判断
136 // // 注意这里的方式是不精确的，适用于文字轴这种类型的
137 // int keyIndex = pickClosest(key, graph->keyAxis()->tickVector());
138 // setText(QString("%1:%2").arg(graph->keyAxis()->tickVectorLabels().at(keyIndex),
139 // QString::number(value)));
140 setText(QString("%1:%2").arg(QString::number(key), QString::number(value)));
141 mHighlightGraph = graph;
142 mGraphDataPos = pos;
143
144 mParentPlot->setCursor(Qt::PointingHandCursor);
145 position->setPixelPosition(newPos); // 更新位置
146 setVisible(true);
147
148 if (replot) update();
149 break;
150 }
151 }
152 }
153
154 if (!mHighlightGraph && visible()) {
155 mParentPlot->setCursor(Qt::ArrowCursor);
156 setVisible(false);
157 if (replot) update();
158 }
159 }
160
161 void QCPToolTip::draw(QCPPainter *painter)
162 {
163 if (mPlotReplot) { // 当前是由QCustomPlot的replot函数刷新的，所以要更新位置
164 updatePosition(position->pixelPosition(), false); // 传入false表明不刷新
165 if (!visible()) return; // 由于位置更新之后，ToolTip可能会隐藏掉了，所以此处直接返回
166 }
167
168 drawGraphScatterPlot(painter, mHighlightGraph, mGraphDataPos);
169
170 QPointF pos = position->pixelPosition() + mOffset;
171 painter->translate(pos); // 移动painter的绘制原点位置
172
173 QFontMetrics fontMetrics(mFont);
174 QRect textRect = fontMetrics.boundingRect(0, 0, 0, 0, Qt::TextDontClip | mTextAlignment, mText);
175 textRect.moveTopLeft(QPoint(mPadding.left(), mPadding.top()));
176
177 QRect textBoxRect = textRect.adjusted(-mPadding.left(), -mPadding.top(), mPadding.right(), mPadding.bottom());
178 textBoxRect.moveTopLeft(QPoint());
179
180 // 限制ToolTip不超过QCustomPlot的范围
181 if (pos.x() + textBoxRect.width() >= mParentPlot->viewport().right())
182 painter->translate(-mOffset.x() * 2 - textBoxRect.width(), 0);
183 if (pos.y() + textBoxRect.height() * 2 >= mParentPlot->viewport().bottom())
184 painter->translate(0, -mOffset.y() * 2 - textBoxRect.height());
185
186 // 绘制背景和边框
187 if ((mBrush != Qt::NoBrush && mBrush.color().alpha() != 0) ||
188 (mBorderPen != Qt::NoPen && mBorderPen.color().alpha() != 0)) {
189 double clipPad = mBorderPen.widthF();
190 QRect boundingRect = textBoxRect.adjusted(-clipPad, -clipPad, clipPad, clipPad);
191
192 painter->setPen(mBorderPen);
193 painter->setBrush(mBrush);
194 painter->drawRoundedRect(boundingRect, mRadius.x(), mRadius.y(), mSizeMode);
195 }
196
197 // 绘制文字
198 painter->setFont(mFont);
199 painter->setPen(mTextColor);
200 painter->setBrush(Qt::NoBrush);
201 painter->drawText(textRect, Qt::TextDontClip | mTextAlignment, mText);
202 }
203
204 void QCPToolTip::drawGraphScatterPlot(QCPPainter *painter, QCPGraph *graph, const QPointF &pos)
205 {
206 if (!graph) return;
207
208 QCPScatterStyle style = graph->scatterStyle();
209 if (style.isNone()) return;
210
211 if (graph->selectionDecorator()) // 如果有select decorator，则使用修饰器的风格
212 style = graph->selectionDecorator()->getFinalScatterStyle(style);
213
214 style.applyTo(painter, graph->pen());
215 style.setSize(style.size() * 1.2); // 放大一点
216 style.drawShape(painter, pos);
217 }