Building Qt Virtual Keyboard

Overview

This document describes how to build the Qt Virtual Keyboard plugin.

The project is split into the following subprojects:

The input methods are implemented either in C++ or QML. Qt Virtual Keyboard provides implementations of PlainInputMethod, MultitapInputMethod and HunspellInputMethod. The MultitapInputMethod is implemented in QML while the others are implemented in C++.

Build Instructions

The Qt Virtual Keyboard can be built for Linux Desktop/X11, Windows Desktop or Boot2Qt targets. The target is automatically detected by QMAKE and requires no special configuration parameters.

Qt Creator is the preferred build environment for Qt Virtual Keyboard as you can then leverage the shadow build functionality and rapidly switch between build targets.

Configuration Options

The table below contains the top-level options for configuring the virtual keyboard features.

Advanced Configuration Options

The table below shows the advanced configuration options that will be applied automatically when activating a certain top-level feature. The options can also be used for enabling or disabling a specific feature.

In most cases, these options are not needed, but there are also cases where their use is justified. For example, the Traditional Chinese language (CONFIG=lang-zh_TW) will include both Zhuyin and Cangjie input methods by default. This behavior can be changed by adding the preferred input method to the configuration, e.g., CONFIG+="lang-zh_TW zhuyin".

Building Documentation

Hunspell Integration

By default, HunspellInputMethod will not be available unless the Hunspell library and development headers are found. For Linux/X11 targets, the Hunspell library can be provided by installing the libhunspell-dev package. Alternatively, the Hunspell sources can be extracted into the src/plugins/hunspell/3rdparty/hunspell directory. The sources are automatically detected by the qmake and the project will be configured to use the local Hunspell. If Hunspell sources are used, then the dictionary files must also be copied into the src/plugins/hunspell/3rdparty/hunspell/data directory.

An example of how the directory structure should look after copying in the Hunspell sources and dictionary files is listed below:

 3rdparty
 └── hunspell
     ├── data
     │   ├── en_GB.aff
     │   └── en_GB.dic
     ├── hunspell.pro
     └── src
         └── hunspell
             ├── affentry.cxx
             ├── affentry.hxx
             (etc.)

T9 Write Integration

T9 Write integration supports the T9 Write Alphabetic and T9 Write CJK engines. Both engines are integrated via T9WriteInputMethod. The input method can be initialized with either of the engines at runtime. The engine selection happens automatically based on input locale and input mode from the keyboard.

T9 Write Compatibility

Qt Virtual Keyboard is compatible with T9 Write v7.5.0 onward.

The latest tested version is v7.8.1.

T9 Write Build Preparations

The contents of the SDK must be either manually copied to the directory structure described below, or by using the unpack.py script found in the t9write directory.

To unpack the SDK using the script:

 $ cd src/plugins/t9write/3rdparty/t9write/
 $ python unpack.py T9Write_Alpha_v7-8-0_SDK.zip .

 3rdparty
 └── t9write
     ├─── api
     │   ├─── decuma*.h
     │   ├─── t9write*.h
     │   └─── xxt9w*.h
     ├─── data
     │   ├─── arabic
     │   │   └─── *.bin [T9 Write Arabic]
     │   ├─── hebrew
     │   │   └─── *.bin [T9 Write Hebrew]
     │   ├─── *.bin [T9 Write Alphabetic]
     │   ├─── *.hdb
     │   ├─── *.phd
     │   └─── *.ldb [T9 Write v7.5]
     └─── lib
         ├─── arm
         │   ├─── shared
         │   │   ├─── alphabetic
         │   │   │   └─── *.so
         │   │   └─── cjk
         │   │       └─── *.so
         │   └─── static
         │       ├─── alphabetic
         │       │   └─── *.a / *.o
         │       └─── cjk
         │           └─── *.a / *.o
         ├─── linux-x86
         │   ├─── shared
         │   │   ├─── alphabetic
         │   │   │   └─── *.so
         │   │   └─── cjk
         │   │       └─── *.so
         │   └─── static
         │       ├─── alphabetic
         │       │   └─── *.a / *.o
         │       └─── cjk
         │           └─── *.a / *.o
         └─── win32
             ├─── shared
             │   ├─── alphabetic
             │   │   ├─── *.dll
             │   │   └─── *.lib
             │   └─── cjk
             │       ├─── *.dll
             │       └─── *.lib
             └─── static
                 ├─── alphabetic
                 │   └─── *.lib / *.obj
                 └─── cjk
                     └─── *.lib / *.obj

Where the contents of each directory are:

Finally, the SDK is included in the build by adding CONFIG+=t9write to the qmake command line.

MyScript Text SDK Integration

MyScript Text is designed for building applications that enable the recognition of handwritten text. MyScript Text supports the recognition of isolated characters, cursive, print and superimposed writing. MyScript superimposed writing is integrated into Qt Virtual Keyboard. It enables the recognition of letters, words or parts of words written one over the other, without any explicit separation between consecutive fragments. It is capable of running on memory and CPU constrained devices.

Input handwriting styles of MyScript Text SDK

The end-user can write one word fragment over the other, or one character over the other, as depicted below. Space between two written words are automatically added, so that there is no need for an explicit gesture.

Language coverage of MyScript Text SDK

MyScript Superimposed supports 70 languages.

MyScript Text SDK Packages Installation

The MyScript delivery team can provide you the packages with various .zip archives. To access all the code, tools, and resources needed for building your own handwriting application, extract all the packages in the same destination folder as src/plugins/myscript/3rdparty/myscript.

The file hierarchy should look like below:

 3rdparty
 └── myscript
     ├─── conf
     ├─── doc
     ├─── edk
     ├─── engine
     │   └─── bin
     │       ├─── lin-arm64
     │       │   └─── *.so
     │       ├─── lin-armv7
     │       │   └─── *.so
     │       ├─── lin-x64
     │       │   └─── *.so
     │       ├─── lin-x86
     │       │   └─── *.so
     │       ├─── win-x64
     │       │   └─── *.dll
     │       ├─── win-x86
     │       │   └─── *.dll
     │       (etc.)
     ├─── rdk
     ├─── resources
     │   ├─── ar
     │   │   └─── *.res
     │   ├─── en_GB
     │   │   └─── *.res
     │   ├─── ja_JP
     │   │   └─── *.res
     │   ├─── ko_KR
     │   │   └─── *.res
     │   ├─── zh_CN
     │   │   └─── *.res
     │   (etc.)
     ├─── tools
     └─── voim
         ├─── api
         ├─── bin
         │   ├─── lin-arm64
         │   │   └─── *.so
         │   ├─── lin-armv7
         │   │   └─── *.so
         │   ├─── lin-x64
         │   │   └─── *.so
         │   ├─── lin-x86
         │   │   └─── *.so
         │   ├─── win-x64
         │   │   └─── *.dll
         │   ├─── win-x86
         │   │   └─── *.dll
         │   (etc.)
         └─── conf

The description for the contents of each directory are:

Setting the Certificate of MyScript Text SDK

A valid certificate is mandatory to use the MyScript Text SDK. This is a security measure that uniquely identifies you as a legitimate customer of MyScript technologies. The certificate helps MyScript trace customers' identify and the products that have been purchased.

The certificate is delivered in the /c [your_login].vo.zip package. When you unzip this package, the certificate is automatically put in the appropriate location. This ensure that the certificate is instantly working within the services and code samples that you have been provided with.

How to build Qt Virtual Keyboard with MyScript Text SDK

The MyScript Text SDK is included in the build of Qt Virtual Keyboard by either adding CONFIG+=handwriting or CONFIG+=myscript to the qmake command line.

Static builds

The virtual keyboard can be built and linked statically against the application. This implies that Qt is also built statically (using the -static option in the configure command line).

Static builds of the virtual keyboard are enabled by adding CONFIG+=static to the qmake command line and then rebuilding.

Some third party modules used by the virtual keyboard are always built as shared libraries. These modules are Hunspell and Lipi Toolkit.

Using the static plugin

The following section should be added to the application project file that uses the statically built virtual keyboard.

 static {
     QTPLUGIN += qtvirtualkeyboardplugin
     QT += svg
 }

QTPLUGIN causes qmake to pull linker dependencies for the virtual keyboard plugin. The SVG module is required as an extra dependency for Qt, since the SVG format is required by the default styles.

From here on, using a statically built virtual keyboard is no different from the normal case.

Deployment

Desktop Targets

Add a Deploy Step that executes the make install command, then deploy using the Deploy All command.

Boot2Qt Targets

The installation is done by copying the necessary files to the memory card, or by using the adb push command.