Qt5 Virtual Keyboard C++ Integration and Implementation

reference:

Building Qt Virtual Keyboard
keyboardDesignWidth and Height

I. Download Source Code

Go to the official github to download the required version of the source code:
https://github.com/qt/qtvirtualkeyboard/releases
The version I downloaded is:
https://github.com/qt/qtvirtualkeyboard/archive/v5.10.0.tar.gz

II. Settings

Configure the required language
1). Configured by Qt Creator
Open the Qt project file and open the left side of the project Projects->Build->Build Steps->qmake->Additional arguments
Add configuration parameters in Additional arguments:
```
CONFIG+="lang-ar_AR lang-da_DK lang-de_DE lang-en_GB lang-es_ES lang-fa_FA lang-fi_FI lang-fr_FR lang-hi_IN lang-it_IT lang-ja_JP lang-ko_KR lang-nb_NO lang-pl_PL lang-pt_PT lang-ru_RU lang-sv_SE lang-zh_CN lang-zh_TW"
```
Select the desired language as needed, of course, if you simply configure it for all languages, then as the following:
```
CONFIG+=lang-all
```
Configure the required language
2). Configure and generate the makefile directly from the command line.
```
/opt/Qt5.10.1/5.10.1/gcc_64/bin/qmake qtvirtualkeyboard.pro -spec linux-g++ 'CONFIG+=lang-all'
```
Specify the linux platform with the -spec parameter.
The virtualkeyboard.pro configuration file add the following content:
```
LIBS+=-L../../lib
```
The reason for this is because when integrating Chinese language, Japanese, etc. with the language of the three-party library, the generated three-party library will not be found when the qtvirtualkeyboard is finally generated. We only need to add a path to solve this problem.

III. C++ integration

In order to use Qt Virtual Keyboard in the traditional QWidget program (corresponding to QML), we only need to add the following code at the entry of the program:

qputenv("QT_IM_MODULE", QByteArray("qtvirtualkeyboard"));

Finally, the program looks like this

int main(int argc, char *argv[])
{
    qputenv("QT_IM_MODULE", QByteArray("qtvirtualkeyboard"));

    QApplication a(argc, argv);
    MainWindow w;
    w.show();

    return a.exec();
}

IV. Customize keyboard size and location

We need to change the InputPanel.qml file

Item {
    id: inputPanel

    property int screenHeight: Screen.desktopAvailableHeight; 
    anchors.fill: parent;

    Keyboard {
        id: keyboard

        anchors.horizontalCenter: parent.horizontalCenter
        width: Screen.desktopAvailableWidth * 2 / 3
        y: getInputY()

        function getInputY(){
            return 0
        }
    }
}

The sample code is shown above, defining the horizontal center position and width of the keyboard. The vertical position of the keyboard is set by y and returned by the getInputY() function. I does not give a concrete implementation. A more general idea can be according to the position of the input box to adapt the position of the keyboard, of course, this also needs to change the c++ code of the qtvirtualkeyboard related files, I will not be described here.