Deployment Guide

Overview

This document describes how to deploy and use the Qt Virtual Keyboard plugin with Qt applications.

Deployment

The various Qt Virtual Keyboard plugins and files are deployed in the following locations:

Dependencies

Read more at Deploying Qt's Libraries.

Integration Method

Qt Virtual Keyboard currently supports two alternative integration methods for using the plugin:

• Desktop: requires no changes to existing applications. The virtual keyboard is available to all Qt applications in the system.

  In this integration method, the keyboard is shown in a dedicated top-level window.

• Application: the virtual keyboard is embedded within the Qt application itself by instantiating an InputPanel item in QML.

  This method is mandatory in environments where there is no support for multiple top-level windows (such as embedded devices), but can be used in desktop applications too.

  This method can also be used by Qt Wayland compositors in order to provide a server-side virtual keyboard. See the section below for details.

The integration method is automatically selected by the project files. However, in desktop environments, it is possible to override the desktop integration method and use the application integration method instead, by using the QT_VIRTUALKEYBOARD_DESKTOP_DISABLE environment variable, or by adding -no-vkb-desktop to the configure command line.

Using Qt Virtual Keyboard with Qt Wayland

This section explains how to use Qt Virtual Keyboard to interact with the Qt Widgets Line Edits example using the Fancy Compositor example as a compositor.

We will be using Ubuntu 18.04 to run the example, using the X11 as the windowing system. The example compositor (fancy-compositor) will open as a window within an X11 session.

1. Start the compositor:

    QT_XCB_GL_INTEGRATION=xcb_egl QT_WAYLAND_CLIENT_BUFFER_INTEGRATION=xcomposite-egl \
    QT_IM_MODULE=qtvirtualkeyboard ./fancy-compositor -platform xcb
   

2. Before running the client application, ensure that QT_IM_MODULE is unset:

    unset QT_IM_MODULE
   

3. Start the Line Edits example as the client:

    ./lineedits -platform wayland
   

4. Click on a line edit and Qt Virtual Keyboard's input panel will open.

If issues are encountered, the following environment variables can be set when running the compositor to get debug output that can help diagnose the issue:

 WAYLAND_DEBUG=1
 QT_LOGGING_RULES="qt.virtualkeyboard=true;qt.qpa.wayland*=true"

Loading the Plugin

In both integration methods, the application must use the QT_IM_MODULE environment variable to load the plugin. For example:

 $ QT_IM_MODULE=qtvirtualkeyboard myapp

or in the main() function:

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

In the desktop integration method, this step is all that is required to use Qt Virtual Keyboard. In the application integration method, the application is required to create an instance of InputPanel as explained in the following chapter.

Creating InputPanel

The following example shows how to create an InputPanel and how to divide the screen area with the application container.

 import QtQuick
 import QtQuick.VirtualKeyboard

 Item {
     id: root
     Item {
         id: appContainer
         anchors.left: parent.left
         anchors.top: parent.top
         anchors.right: parent.right
         anchors.bottom: inputPanel.top
         ...
     }
     InputPanel {
         id: inputPanel
         y: Qt.inputMethod.visible ? parent.height - inputPanel.height : parent.height
         anchors.left: parent.left
         anchors.right: parent.right
     }
 }

The input panel must be a sibling element next to the application container. It is important not to put the input panel within the application container, as it would then overlap with the contents of the application. Also, the input panel height will be automatically updated according to the available width; the aspect ratio of the input panel is constant.

Environment Variables

There are several environment variables defined by the module that are listed below: