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diff --git a/doc/src/examples/inputpanel.qdoc b/doc/src/examples/inputpanel.qdoc new file mode 100644 index 0000000000..53051085cb --- /dev/null +++ b/doc/src/examples/inputpanel.qdoc @@ -0,0 +1,224 @@ +/**************************************************************************** +** +** Copyright (C) 2011 Nokia Corporation and/or its subsidiary(-ies). +** All rights reserved. +** Contact: Nokia Corporation (qt-info@nokia.com) +** +** This file is part of the documentation of the Qt Toolkit. +** +** $QT_BEGIN_LICENSE:FDL$ +** No Commercial Usage +** This file contains pre-release code and may not be distributed. +** You may use this file in accordance with the terms and conditions +** contained in the Technology Preview License Agreement accompanying +** this package. +** +** GNU Free Documentation License +** Alternatively, this file may be used under the terms of the GNU Free +** Documentation License version 1.3 as published by the Free Software +** Foundation and appearing in the file included in the packaging of this +** file. +** +** If you have questions regarding the use of this file, please contact +** Nokia at qt-info@nokia.com. +** $QT_END_LICENSE$ +** +****************************************************************************/ + +/*! + \example tools/inputpanel + \title Input Panel Example + + The Input Panel example shows how to create an input panel that + can be used to input text into widgets using only the pointer and + no keyboard. + + \image inputpanel-example.png + + The input fields in the main window have no function other than + to accept input. The main focus is on how the extra input panel + can be used to input text without the need for a real keyboard or + keypad. + + \section1 Main Form Class Definition + + Because the main window has no other function than to accept + input, it has no class definition. Instead, its whole layout is + made in Qt Designer. This emphasizes the point that no widget + specific code is needed to use input panels with Qt. + + \section1 MyInputPanelContext Class Definition + + \snippet examples/tools/inputpanel/myinputpanelcontext.h 0 + + The \c MyInputPanelContext class inherits QInputContext, which is + Qt's base class for handling input methods. + \c MyInputPanelContext is responsible for managing the state of + the input panel and sending input method events to the receiving + widgets. + + The \c inputPanel member is a pointer to the input panel widget + itself; in other words, the window that will display the buttons + used for input. + + The \c identifierName(), \c language(), \c isComposing() and + \c reset() functions are there mainly to fill in the pure virtual + functions in the base class, QInputContext, but they can be + useful in other scenarios. The important functions and slots are + the following: + + \list + \o \c filterEvent() is where we receive events telling us to open + or close the input panel. + \o \c sendCharacter() is a slot which is called when we want to + send a character to the focused widget. + \o \c updatePosition() is used to position the input panel + relative to the focused widget, and will be used when opening + the input panel. + \endlist + + \section1 MyInputPanelContext Class Implementation + + In the constructor we connect to the \c characterGenerated() + signal of the input panel, in order to receive key presses. We'll + see how it works in detail later on. + + \snippet examples/tools/inputpanel/myinputpanelcontext.cpp 0 + + In the \c filterEvent() function, we must look for the two event + types: \c RequestSoftwareInputPanel and \c CloseSoftwareInputPanel. + + \snippet examples/tools/inputpanel/myinputpanelcontext.cpp 1 + + 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 \c updatePosition() \mdash we'll see later on what it + does \mdash then show the actual input panel widget. If we receive + the \c CloseSoftwareInputPanel event, we do the opposite, and + hide the input panel. + + \snippet examples/tools/inputpanel/myinputpanelcontext.cpp 2 + + We implement the \c sendCharacter() function so that it sends the + supplied character to the focused widget. All QInputContext based + classes are always supposed to send events to the widget returned + by QInputContext::focusWidget(). Note the QPointer guards to make + sure that the widget does not get destroyed in between events. + + Also note that we chose to use key press events in this example. + For more complex use cases with composed text it might be more + appropriate to send QInputMethodEvent events. + + The \c updatePosition() function is implemented to position the + actual input panel window directly below the focused widget. + + \snippet examples/tools/inputpanel/myinputpanelcontext.cpp 3 + + It performs the positioning by obtaining the coordinates of the + focused widget and translating them to global coordinates. + + \section1 MyInputPanel Class Definition + + The \c MyInputPanel class inherits QWidget and is used to display + the input panel widget and its buttons. + + \snippet examples/tools/inputpanel/myinputpanel.h 0 + + If we look at the member variables first, we see that there is + \c 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 \c NoFocus focus policy so that we can + maintain focus on the window receiving input instead of the + window containing buttons. + + The \c lastFocusedWidget is a helper variable, which also aids in + maintaining focus. + + \c 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 \c MyInputPanel are the + following: + + \list + \o \c event() is used to intercept and manipulate focus events, + so we can maintain focus in the main window. + \o \c saveFocusWidget() is a slot which will be called whenever + focus changes, and allows us to store the newly focused widget + in \c lastFocusedWidget, so that its focus can be restored + if it loses it to the input panel. + \o \c buttonClicked() is a slot which will be called by the + \c signalMapper whenever it receives a \c clicked() signal + from any of the buttons. + \endlist + + \section1 MyInputPanel Class Implementation + + If we look at the constructor first, we have a lot of signals to + connect to! + + We connect the QApplication::focusChanged() signal + to the \c saveFocusWidget() signal in order to get focus updates. + Then comes the interesting part with the signal mapper: the + series of \c 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. + + \snippet examples/tools/inputpanel/myinputpanel.cpp 0 + + The next series of connections then connect each button's + \c clicked() signal to the signal mapper. Finally, we create + a connection from the \c mapped() signal to the + \c buttonClicked() slot, where we will handle it. + + \snippet examples/tools/inputpanel/myinputpanel.cpp 3 + + In the \c 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 \c characterGenerated() + signal, which \c MyInputPanelContext is connected to. This will + in turn cause it to send the input to the focused widget. + + In the \c saveFocusWidget() slot, we test whether the newly + focused widget is a child of the input panel or not, using the + QWidget::isAncestorOf() call. + + \snippet examples/tools/inputpanel/myinputpanel.cpp 2 + + 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 \c event() function we handle QEvent::WindowActivate + event, which occurs if the focus switches to the input panel. + + \snippet examples/tools/inputpanel/myinputpanel.cpp 1 + + 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. + + \section1 Setting the Input Context + + The main function for the example is very similar to those for other + examples. The only real difference is that it creates a + \c MyInputPanelContext and sets it as the application-wide input + context. + + \snippet examples/tools/inputpanel/main.cpp main + + With the input context in place, we set up and show the user interface + made in Qt Designer before running the event loop. + + \section1 Further Reading + + 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. +*/ |