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Diffstat (limited to 'examples/bars/doc/src/bars.qdoc')
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1 files changed, 154 insertions, 2 deletions
diff --git a/examples/bars/doc/src/bars.qdoc b/examples/bars/doc/src/bars.qdoc index 1db72e47..a8de709b 100644 --- a/examples/bars/doc/src/bars.qdoc +++ b/examples/bars/doc/src/bars.qdoc @@ -22,9 +22,161 @@ \ingroup qtdatavisualization_examples \brief Using an item model as data source for Q3DBars. - The bars example shows how to make a simple 3D bar graph using Q3DBars. + The bars example shows how to make a simple 3D bar graph using Q3DBars and how to modify the + data being drawn at run-time. The example shows how to: + + \list + \li How to create an application with Q3DBars and widgets + \li How to use QItemModelBarDataMapping and QItemModelBarDataProxy to set data to the graph + \li How to use a table widget to modify the data in the graph + \endlist + + \image bars-example-2.png + + \section1 Creating the application + + First, in main.cpp, we create a QApplication, instantiate Q3DBars and a window container for it: + + \snippet ../examples/bars/main.cpp 0 + + The call to QWidget::createWindowContainer is required, as all data visualization types + (Q3DBars, Q3DScatter, Q3DSurface) inherit QWindow. Any class inheriting QWindow cannot be used + as a widget any other way. + + Then we'll create a layout and add the graph and the table widget into it: + + \snippet ../examples/bars/main.cpp 1 + + The table widget is going to be used to display the numerical data being inserted into the + graph, and to modify it (See \l {Adding data to the graph} and \l {Interacting with the data}). + + We need to instantiate QItemModelBarDataMapping and QItemModelBarDataProxy and give them to the + graph: + + \snippet ../examples/bars/main.cpp 2 + + Here we tell the mapping object to directly map model's rows and columns into proxy's rows and + columns instead of defining row and column roles to map for them. Then we give the model from + the table widget and the mapping object to the proxy. Finally we set the proxy as the active + data proxy for the graph. + + Next, let's create another class to handle the data addition and other interaction with the + graph. Let's call it GraphDataGenerator (See \l {Setting up the graph} and + \l {Adding data to the graph} for details) and connect some signals between Q3DBars, + GraphDataGenerator and QTableWidget (See \l {Interacting with the data} for a closer look): + + \snippet ../examples/bars/main.cpp 3 + + The application main is done and we can show the graph and start the event loop: + + \snippet ../examples/bars/main.cpp 4 + + \section1 Setting up the graph + + Let's set up the visual attributes for the graph in the constructor of GraphDataGenerator: + + \snippet ../examples/bars/main.cpp 5 + \snippet ../examples/bars/main.cpp 6 + \snippet ../examples/bars/main.cpp 7 + + First we set bar thickness ratio to 1.0, which means bars will be as wide as they are deep. 1.0 + is also the default value, so the line is basically unnecessary. It's left there so you could + easily try how changing it affects the graph. The second line sets bar spacings to 0.2, which + means there will be a gap of 20% of the bar's thickness between the bars in both directions. + + Then, we set the bar type to flat pyramids, overriding the default bar type. + We want to be able to select rows of data for a closer inspection, so we set the selection mode + to slice row. This means that whenever we select a bar in the graph, the whole row will be + displayed separately. + + Next line sets the font to \c Impact. If your system doesn't have it, it will be replaced by + system default. + + And finally, we set theme to \c Digia and camera position to \c {Preset Front}. Now the initial + graph settings are done. + + \note You do not need to set any of these in case you're happy with the defaults. You can + easily try them by commenting out the contents of the constructor. + + \section1 Adding data to the graph + + We created the data generator in the application main and gave it the graph and the table + widget as parameters: + + \code GraphDataGenerator generator(graph, tableWidget); \endcode + + We added a separate start method to the generator, so that it wouldn't start doing anything + until everything else is set up. We then called the method when starting the application: + + \code generator.start(); \endcode + + Let's have a look at the contents of the \c start() method: + + \snippet ../examples/bars/main.cpp 8 + + The main thing \c start() does is set up the data model. It also activates a timer for getting + the accurate dimensions of the table widget after it's been filled with data. The reason we + do this is that the widget doesn't know its final visual domensions until all the data has been + inserted to it and it has been shown. The whole data timer implementation is not vital for the + application, so we won't take a closer look at it. It's just there to make the table look better. + + In \c setupModel() we first introduce the row and column labels, and the actual data: + + \snippet ../examples/bars/main.cpp 9 + + Then we set up the axes: + + \snippet ../examples/bars/main.cpp 10 + + The other lines there are pretty self-explanatory except for the one with the segment count. + We're setting it to five as we want the value axis (the Y-axis) to show more values than just + the lowest and the highest. + + Next we will set up the table widget: + + \snippet ../examples/bars/main.cpp 11 + + After that all that's left is adding the data to the table widget: + + \snippet ../examples/bars/main.cpp 12 + + Now we have a bar graph and a table widget, both displaying the same data. + + You're probably wondering how the data can be displayed in the graph, as the only thing we did + was add it to the table widget? That's because of what we did earlier, in the application main: + + \snippet ../examples/bars/main.cpp 2 + + We created QItemModelBarDataMapping and QItemModelBarDataProxy instances, and gave the proxy + the model of the table widget and the model mapping we just created. Then we set the proxy as + the active proxy for the graph. The proxy maps the rows and the columns in the model of the table + widget into rows and columns for itself using the model mapping, and the graph gets the data + to be displayed from its active proxy. + + \section1 Interacting with the data + + We made a couple of signal connections in the application main earlier: + + \snippet ../examples/bars/main.cpp 3 + + Now we'll find out what these were for. + + The first one connects a signal from Q3DBars to the GraphDataGenerator. Signal + Q3DBars::selectedBarPosChanged() is emitted when a bar is selected from the graph. We connect + that to a method in the data generator that selects the same data item in the table widget: + + \snippet ../examples/bars/main.cpp 13 + + The second connection does the opposite; it connects a signal from the table widget to a + method in the data generator. The method then selects the corresponding bar in the graph: + + \snippet ../examples/bars/main.cpp 14 + + You can even select an item in the widget and change the value of it, and the new value is + updated to the graph. This is handled again by the active proxy with mapping between the data + in the table widget and itself. \image bars-example.png - TODO + \section1 Example contents */ |