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In the constructor we connect to the characterGenerated() signal of the input panel, in order to receive key presses. We'll see how it works in detail later on.
MyInputPanelContext::MyInputPanelContext()
{
inputPanel = new MyInputPanel;
connect(inputPanel, SIGNAL(characterGenerated(QChar)), SLOT(sendCharacter(QChar)));
}
In the filterEvent() function, we must look for the two event types: RequestSoftwareInputPanel and CloseSoftwareInputPanel.
bool MyInputPanelContext::filterEvent(const QEvent* event)
{
if (event->type() == QEvent::RequestSoftwareInputPanel) {
updatePosition();
inputPanel->show();
return true;
} else if (event->type() == QEvent::CloseSoftwareInputPanel) {
inputPanel->hide();
return true;
}
return false;
}
The first type will be sent whenever an input capable widget wants to ask for an input panel. Qt's input widgets do this automatically. If we receive that type of event, we call updatePosition() — we'll see later on what it does — then show the actual input panel widget. If we receive the CloseSoftwareInput, T e%, 7 T /P0/3 % $ ( 4HE )U P%
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@@ @ D @ @ @ B ! @ $ @ D @ @ @ @ @ @ @ @ ! @ @ $ A@@ @ @ @@" @ @ @ @ @D @ @ @ @ ! @ @ ! `@ 0 @ @ @ @A @ @ H @ @ H B @ 8 class MyInputPanel : public QWidget
{
Q_OBJECT
public:
MyInputPanel();
signals:
void characterGenerated(QChar character);
protected:
bool event(QEvent *e);
private slots:
void saveFocusWidget(QWidget *oldFocus, QWidget *newFocus);
void buttonClicked(QWidget *w);
private:
Ui::MyInputPanelForm form;
QWidget *lastFocusedWidget;
QSignalMapper signalMapper;
};
If we look at the member variables first, we see that there is form, which is made with Qt Designer, that contains the layout of buttons to click. Note that all the buttons in the layout have been declared with the NoFocus focus policy so that we can maintain focus on the window receiving input instead of the window containing buttons.
The lastFocusedWidget is a helper variable, which also aids in maintaining focus.
signalMapper is an instance of the QSignalMapper class and is there to help us tell which button was clicked. Since they are all very similar this is a better solution than creating a separate slot for each one.
The functions that we implement in MyInputPanel are the following:
If we look at the constructor first, we have a lot of signals to connect to!
We connect the QApplication::focusChanged() signal to the saveFocusWidget() signal in order to get focus updates. Then comes the interesting part with the signal mapper: the series of setMapping() calls sets the mapper up so that each signal from one of the buttons will result in a QSignalMapper::mapped() signal, with the given widget as a parameter. This allows us to do general processing of clicks.
MyInputPanel::MyInputPanel()
: QWidget(0, Qt::Tool | Qt::WindowStaysOnTopHint),
lastFocusedWidget(0)
{
form.setupUi(this);
connect(qApp, SIGNAL(focusChanged(QWidget*,QWidget*)),
this, SLOT(saveFocusWidget(QWidget*,QWidget*)));
signalMapper.setMapping(form.panelButton_1, form.panelButton_1);
signalMapper.setMapping(form.panelButton_2, form.panelButton_2);
signalMapper.setMapping(form.panelButton_3, form.panelButton_3);
signalMapper.setMapping(form.panelButton_4, form.panelButton_4);
signalMapper.setMapping(form.panelButton_5, form.panelButton_5);
signalMapper.setMapping(form.panelButton_6, form.panelButton_6);
signalMapper.setMapping(form.panelButton_7, form.panelButton_7);
signalMapper.setMapping(form.panelButton_8, form.panelButton_8);
signalMapper.setMapping(form.panelButton_9, form.panelButton_9);
signalMapper.setMapping(form.panelButton_star, form.panelButton_star);
signalMapper.setMapping(form.panelButton_0, form.panelButton_0);
signalMapper.setMapping(form.panelButton_hash, form.panelButton_hash);
connect(form.panelButton_1, SIGNAL(clicked()),
&signalMapper, SLOT(map()));
connect(form.panelButton_2, SIGNAL(clicked()),
&signalMapper, SLOT(map()));
connect(form.panelButton_3, SIGNAL(clicked()),
&signalMapper, SLOT(map()));
connect(form.panelButton_4, SIGNAL(clicked()),
&signalMapper, SLOT(map()));
connect(form.panelButton_5, SIGNAL(clicked()),
&signalMapper, SLOT(map()));
connect(form.panelButton_6, SIGNAL(clicked()),
&signalMapper, SLOT(map()));
connect(form.panelButton_7, SIGNAL(clicked()),
&signalMapper, SLOT(map()));
connect(form.panelButton_8, SIGNAL(clicked()),
&signalMapper, SLOT(map()));
connect(form.panelButton_9, SIGNAL(clicked()),
&signalMapper, SLOT(map()));
connect(form.panelButton_star, SIGNAL(clicked()),
&signalMapper, SLOT(map()));
connect(form.panelButton_0, SIGNAL(clicked()),
&signalMapper, SLOT(map()));
connect(form.panelButton_hash, SIGNAL(clicked()),
&signalMapper, SLOT(map()));
connect(&signalMapper, SIGNAL(mapped(QWidget*)),
this, SLOT(buttonClicked(QWidget*)));
}
The next series of connections then connect each button's clicked() signal to the signal mapper. Finally, we create a connection from the mapped() signal to the buttonClicked() slot, where we will handle it.
void MyInputPanel::buttonClicked(QWidget *w)
{
QChar chr = qvariant_cast<QChar>(w->property("buttonValue"));
emit characterGenerated(chr);
}
In the buttonClicked() slot, we extract the value of the "buttonValue" property. This is a custom property which was created in Qt Designer and set to the character that we wish the button to produce. Then we emit the characterGenerated() signal, which MyInputPanelContext is connected to. This will in turn cause it to send the input to the focused widget.
In the saveFocusWidget() slot, we test whether the newly focused widget is a child of the input panel or not, using the QWidget::isAncestorOf() call.
void MyInputPanel::saveFocusWidget(QWidget * /*oldFocus*/, QWidget *newFocus)
{
if (newFocus != 0 && !this->isAncestorOf(newFocus)) {
lastFocusedWidget = newFocus;
}
}
If it isn't, it means that the widget is outside the input panel, and we store a pointer to that widget for later.
In the event() function we handle QEvent::WindowActivate event, which occurs if the focus switches to the input panel.
case QEvent::WindowActivate:
if (lastFocusedWidget)
lastFocusedWidget->activateWindow();
break;
Since we want avoid focus on the input panel, we immediately call QWidget::activateWindow() on the widget that last had focus, so that input into that widget can continue. We ignore any other events that we receive.
The main function for the example is very similar to those for other examples. The only real difference is that it creates a MyInputPanelContext and sets it as the application-wide input context.
#include "myinputpanelcontext.h"
#include "ui_mainform.h"
int main(int argc, char **argv)
{
QApplication app(argc, argv);
MyInputPanelContext *ic = new MyInputPanelContext;
app.setInputContext(ic);
QWidget widget;
Ui::MainForm form;
form.setupUi(&widget);
widget.show();
return app.exec();
}
With the input context in place, we set up and show the user interface made in Qt Designer before running the event loop.
This example shows a specific kind of input context that uses interaction with a widget to provide input for another. Qt's input context system can also be used to create other kinds of input methods. We recommend starting with the QInputContext documentation if you want to explore further.
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