mirror of
https://github.com/jkriege2/JKQtPlotter.git
synced 2024-12-25 18:11:38 +08:00
91 lines
4.2 KiB
Markdown
91 lines
4.2 KiB
Markdown
|
# Example (JKQTPlotter): Using a QScrollbar together with JKQtPlotter {#JKQTPlotterUIScrollbar}
|
||
|
|
This project (see `./examples/ui_bind_scrollbar/`) shows how to use JKQTPlotter together with a <a href="https://doc.qt.io/qt-6/qscrollbar.html">QScrollBar</a> for panning.
|
||
|
|
|
||
|
|
The source code of the main application can be found in [`ui_bind_scrollbar.cpp`](https://github.com/jkriege2/JKQtPlotter/tree/master/examples/ui_bind_scrollbar/ui_bind_scrollbar.cpp).
|
||
|
|
|
||
|
|
First we create a QWidget, a plot and a QScrollBar in a layout:
|
||
|
|
|
||
|
|
```.cpp
|
||
|
|
QWidget win;
|
||
|
|
QVBoxLayout* lay=new QVBoxLayout();
|
||
|
|
win.setLayout(lay);
|
||
|
|
|
||
|
|
JKQTPlotter* plot=new JKQTPlotter(&win);
|
||
|
|
lay->addWidget(plot);
|
||
|
|
// add a QScrollBar below the plot
|
||
|
|
QScrollBar* scroll=new QScrollBar(Qt::Horizontal, &win);
|
||
|
|
scroll->setMinimum(0);
|
||
|
|
scroll->setMaximum(100);
|
||
|
|
scroll->setPageStep(10);
|
||
|
|
lay->addWidget(scroll);
|
||
|
|
```
|
||
|
|
|
||
|
|
Then we add a plot ranging from x=0 to x=100, with 10000 datapoints:
|
||
|
|
|
||
|
|
```.cpp
|
||
|
|
// 4. create a graph
|
||
|
|
JKQTPDatastore* ds=plot->getDatastore();
|
||
|
|
const int NPOINTS=10000;
|
||
|
|
JKQTPXYLineGraph* graph=new JKQTPXYLineGraph(plot);
|
||
|
|
const size_t colX=ds->addLinearColumn(NPOINTS, 0, 100, "x");
|
||
|
|
graph->setXColumn(colX);
|
||
|
|
graph->setYColumn(ds->addCalculatedColumnFromColumn(colX, [](double x) { return 10.0*sin(x*3.0)*fabs(cos((x/8.0))); }, "f(x)"));
|
||
|
|
graph->setDrawLine(true);
|
||
|
|
graph->setSymbolType(JKQTPNoSymbol);
|
||
|
|
// ... add the graphs to the plot, so it is actually displayed
|
||
|
|
plot->addGraph(graph);
|
||
|
|
```
|
||
|
|
|
||
|
|
The plot axis range is limited to the plot range and zooming in y-direction is disabled
|
||
|
|
|
||
|
|
```.cpp
|
||
|
|
plot->setAbsoluteXY(0,100,-10,10);
|
||
|
|
// show everything in y-direction
|
||
|
|
plot->setY(-10,10);
|
||
|
|
// fix y-range, so no zoming occurs in y
|
||
|
|
plot->getYAxis()->setRangeFixed(true);
|
||
|
|
```
|
||
|
|
|
||
|
|
Now we need a slot for the QScrollBar (here implemented as a functor), which calculates the desired view in the graph and sets it. Note the blockSignals()-calls that stop the plot from sending signals back to the scrollbar, which would cause a strange loop due to the fact that the scrollbar only accepts integers for range and value!
|
||
|
|
|
||
|
|
```.cpp
|
||
|
|
QObject::connect(scroll, &QScrollBar::valueChanged, [plot,scroll](int value) {
|
||
|
|
const double scrollRange=scroll->maximum()-scroll->minimum()+scroll->pageStep();
|
||
|
|
const double scrollPos=scroll->value();
|
||
|
|
const double scrollPageSize=scroll->pageStep();
|
||
|
|
const double scrollRelative=scrollPos/scrollRange;
|
||
|
|
const double plotFullRange=plot->getAbsoluteXMax()-plot->getAbsoluteXMin();
|
||
|
|
const double plotViewRange=scrollPageSize/scrollRange*plotFullRange;
|
||
|
|
const double plotViewStart=plot->getAbsoluteXMin()+scrollRelative*plotFullRange;
|
||
|
|
plot->blockSignals(true);
|
||
|
|
plot->setX(plotViewStart, plotViewStart+plotViewRange);
|
||
|
|
plot->blockSignals(false);
|
||
|
|
});
|
||
|
|
scroll->setValue(1); // ensure to call slot once!
|
||
|
|
```
|
||
|
|
|
||
|
|
A second functor catches whenever the user zooms or pans (or otherwise changes the axis ranges) of the plot by catching the signal JKQTPlotter::zoomChangedLocally() and from that calculates the value (and pageStep) for the QScrollBar:
|
||
|
|
|
||
|
|
```.cpp
|
||
|
|
QObject::connect(plot, &JKQTPlotter::zoomChangedLocally, [scroll](double newxmin, double newxmax, double newymin, double newymax, JKQTPlotter* plot) {
|
||
|
|
const double plotFullRange=plot->getAbsoluteXMax()-plot->getAbsoluteXMin();
|
||
|
|
const double plotViewRange=newxmax-newxmin;
|
||
|
|
const double plotRelViewRange=(plotViewRange>=plotFullRange)?1.0:(plotViewRange/(plotFullRange-plotViewRange));
|
||
|
|
const double plotRelViewStart=(newxmin-plot->getAbsoluteXMin())/plotFullRange;
|
||
|
|
const double scrollRange=scroll->maximum()-scroll->minimum();
|
||
|
|
scroll->blockSignals(true);
|
||
|
|
scroll->setPageStep(plotRelViewRange*scrollRange);
|
||
|
|
scroll->setValue(plotRelViewStart*scrollRange);
|
||
|
|
scroll->blockSignals(false);
|
||
|
|
});
|
||
|
|
```
|
||
|
|
|
||
|
|
The window from this example looks like this:
|
||
|
|
|
||
|
|
|
||
|
|
|
||
|
|
|
||
|
|
With the same method, it is also possible to add x- and y-scrollbars:
|
||
|
|
|
||
|
|
|