ChartDirector 5.1 (C++ Edition)
Using ChartDirector with QT
This section describes how to use ChartDirector with QT.
QT Sample Programs
ChartDirector comes with a number of QT sample programs in the "ChartDirector/qtdemo" subdirectory.
Project Name | Description
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helloworld | The "Hello World" example of using ChartDirector with QT. This is a basic QT project displaying a simple bar chart.
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qtdemo | The main QT sample program, containing a chart browser for browsing over 100 sample charts.
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financedemo | An interactive financial chart will comprehensive technical indicators support.
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tracklegend | Demonstrates a sweep line track cursor with dynamic legend entries for the data points at the cursor position.
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tracklabel | Demonstrates a sweep line track cursor with dynamic labels for the data points at the cursor position.
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trackaxis | Demonstrates a sweep line track cursor with dynamic axis labels for the data points at the cursor position.
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trackbox | Demonstrates a track rectangle and a floating legend box for the data points in the rectangle.
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trackfinance | A finance chart with a sweep line track cursor and dynamic legend entries for the price and technical indicator values at the cursor position.
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crosshair | Demonstrates a crosshair cursor with dynamic axis labels showing the position of the cursor.
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realtimedemo | A simple realtime chart with configurable update rate from 250ms to 2 sec.
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realtimetrack | A realtime chart with configurable update rate and a sweep line track cursor that displays dynamic legend entries.
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simplezoomscroll | A simple zoomable and scrollable chart that uses mouse click and drag to control zooming and scrolling.
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zoomscrolltrack | Demonstrates using mouse click and drag, mouse wheel, and a scrollbar to control zooming and scrolling. There is also a sweep line track cursor that displays dynamic legend entries.
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zoomscrolltrack2 | Demonstrates using mouse click and drag, mouse wheel, and a scrollbar to control zooming and scrolling. The axis range can also be set using date picker controls, and there is also a sweep line track cursor that displays dynamic data labels.
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xyzoomscroll | Demonstrates using mouse click and drag, mouse wheel, a slider, and a navigation pad to control zooming and scrolling.
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ChartDirector is GUI framework neutral and works with any GUI framework and version. However, the QT sample programs are only tested on QT 4.6. They may or may not require modifications with other QT versions.
The QT ".pro" project files can be opened directly with the QT Creator or the Visual Studio QT Plug-in. You may also use qmake/make to compile the sample programs from the command line.
It is recommended you start with the helloworld project and then the qtdemo project. The qtdemo project contains over 100 sample charts illustrating various chart types and how to use ChartDirector in general. The charts are from simple to sophisticated, and are designed for use as tutorials.
Important Note For Mac OS X By default, on Mac OS X, qmake will create an Xcode project file, not a make file. To create a make file, please use the "-spec macx-g++" flag:
qmake -spec macx-g++
make
If you must use Xcode, note that the Xcode project file created by qmake is incomplete. It lacks the post link script (according to QT's web site, it is a known issue as of QT 4.6). The post link script is used to copy "libchartdir.5.dylib" to the application bundle, so that the program can find it at runtime.
To solve the problem, you may copy "libchartdir.5.dylib" to "/usr/lib" so that the executable can find it.
For the qtdemo sample program, if it is executed in Xcode, it may be unable to find the required PNG and GIF files, causing some charts to generate incorrectly. It is because Xcode will build and execute the program in another directory (eg. in the build/Debug directory). To solve the problem, please copy the PNG and GIF files from the qtdemo sample code directory to the directory used by Xcode to execute the program.
The QChartViewer Widget
All ChartDirector QT sample programs uses the
QChartViewer widget to display charts and handle mouse interactions. The QChartViewer is a derived class of the QLabel. It is released in source code format.
To use QChartViewer in your own project:
Displaying Charts On Screen
To display a chart using QChartViewer, only one line of code is needed:
// m_ChartViewer is a QChartViewer widget; myChart is a BaseChart pointer
m_ChartViewer.setChart(myChart);
Handling Hot Spots Mouse Interactions
Hot spots are special regions in on the chart that are usually used to represent chart objects, such as data representation objects (sectors for pie chart, bars for bar charts, etc). One can display tool tips when the mouse is over the hot spots, and/or to make the hot spots clickable with mouse cursor feedback.
In ChartDirector, hot spots for the charts are defined using standard HTML image maps (text strings containing HTML
tags). The
BaseChart.getHTMLImageMap method can be used to generate image maps automatically for a chart. To set the image map to the CChartViewer control, one may use:
After setting the image map, the QChartViewer widget will display the tool tips defined in the image map when the mouse is over the hot spots. For clickable hot spots, it will also change the mouse cursor into a "hand" shape.
When the mouse clicks on the QChartViewer widget, a
QChartViewer.clicked signal will be emitted. The signal handler can use
ImageMapHandler to determine which hot spot has been clicked. An example is like:
void CMyDialog::OnChartClicked(QMouseEvent*)
{
// Get the ImageMapHandler from the QChartViewer that sends the signal
QChartViewer *viewer = (QChartViewer *)QObject::sender();
ImageMapHandler *handler = viewer->getImageMapHandler();
if (0 != handler)
{
// Query the ImageMapHandler to see if the mouse is on a clickable
// hot spot. We consider the hot spot as clickable if its href
// ("path") parameter is not empty.
const char *path = handler->getValue("path");
if ((0 != path) && (0 != *path))
{
// In a clickable hot spot - do something ......
// In the sample code, we just show all hot spot parameters using
// the HotSpotDialog included in the sample code.
HotSpotDialog hs;
hs.setData(handler);
hs.exec();
}
}
}
Adding Track Cursor to the Chart
In ChartDirector, track cursors can be created by drawing them on a "dynamic layer" when the mouse moves on the chart. For example, drawing a horizontal line and a vertical line will create a crosshair cursor that tracks the mouse. Other things, such as legend entries, data labels and axis labels, can also be drawn, allowing them to update as the mouse moves over the chart.
QChartViewer will email
QChartViewer.mouseMovePlotArea signals when the mouse moves over the extended plot area. The track cursor drawing code can be implemented in the handler of this signal.
Handling View Port Interactions
A view port can be imagined as a window to an underlying surface. For example, a data series with 10 years of data can be imagined as a long surface. If only 1 year of data is displayed, we may consider this as the view port showing 10% of the underlying surface.
Scrolling can be handled as moving the view port, while zooming in and out can be handled as changing the view port size.
QChartViewer supports using mouse click and drag to control the view port (see
QChartViewer.setMouseUsage). When the view port is changed by mouse actions, QChartViewer will emit a
QChartViewer.viewPortChanged signal. The signal handler can then redraw the chart to reflect the updated view port.
QChartViewer also includes methods for changing the view port programmatically. This allows external controls (such as scroll bars, mouse wheel, sliders, date picker, etc) to manipulate the view port.
Printing Charts On Paper
To print a chart, simply print the QPixmap in the QChartViewer with QPrinter. For example:
QPrinter printer;
QPainter painter;
painter.begin(&printer);
painter.drawImage(40, 40, m_ChartViewer.pixmap()->toImage());
painter.end();
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