Development/Tutorials/Plasma4/QML/GettingStarted: Difference between revisions

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    == Abstract ==
    == Abstract ==


    Writing a plasma applet in QML is very easy, in fact, with KDE 4.6 and Qt 4.7 it just works.
    Writing a Plasma applet in QML is very easy, in fact, with Workspaces 4.6 and Qt 4.7 it just works.
     
    == QML Basics ==
     
    It is recommended that you have read through the [http://qt-project.org/doc/qt-4.8/qtquick.html Qt QML Tutorials], as there are quite a few and they are explained thoroughly. There is also a list of all [http://qt-project.org/doc/qt-4.8/qdeclarativeelements.html standard QML elements].
     
    Essentially, most of the content is the same. The exceptions to be noted are how data is gathered... since we use Data Engines, it is a bit different. Text color and font should be made to use PlasmaCore.Theme.
     
    See the [https://projects.kde.org/projects/kde/kdeexamples/repository KDE Examples] repository for more KDE-related helpful resources. Also of use (which use QML and Plasma) are: [https://projects.kde.org/projects/playground/base/plasma-mobile/repository Plasma Mobile], [https://projects.kde.org/projects/playground/base/declarative-plasmoids/repository Declarative Plasmoids (playground)], for WIP ports of C++ originals.
     
    === Root Item ===
     
    The root item can be anything that inherits QGraphicsItem. For example, in this case it is QGraphicsWidget which is a plasmoid. It can also simply be an Item. I also noticed that PathView does not respond to mouse inputs automatically (so flicking doesn't work). Probably because events are being intercepted. So take note, it'll have to be e.g. an Item, for that case.
     
    === Layouts ===
     
    ==== Row and Column ====
    Coloums and Rows are very easy way to grouping items and is very simular to the "normal layout management" with [http://doc.qt.digia.com/stable/qhboxlayout.html QHBoxLayout] and [http://doc.qt.digia.com/stable/qvboxlayout.html  QVBoxLayout]. In QML these are named:
     
    * Column arranges its children in a column
    * Row arranges its children in a row
    * Grid arranges its children in a grid
    * Flow arranges its children like words on a page
     
    They have a special property '''spacing'''(int) to define the distance in pixels between two children.
     
    For furture help please look at [http://qt-project.org/doc/qt-4.8/qml-positioners.html Using QML Positioner and Repeater Items from qt-project.org]
     
    Some example:
    <syntaxhighlight lang="javascript">
    import QtQuick 1.0
    import org.kde.plasma.core 0.1 as PlasmaCore
     
    Item {
            Column{
                    spacing: 10
                    Row { 
                            spacing: 5
                            Text{text: 'Local'}
                            Text {
                                    id: local
                                    text: "XX:XX:XX"
                            }
                    }
                    Row { 
                            spacing: 5
                            Text{text: 'UTC'}
                            Text {
                                    id: utc
                                    text: "XX:XX:XX"
                            }
                    }
            }
    }
    </syntaxhighlight>
    ==== Anchors ====
    Anchor layouts offer a nice way of grouping UI elements nicely together. The idea is that you connect edges or corners of one element to the edge or corner of another widget. Available anchors are:
    * left
    * horizontalCenter
    * right
    * top
    * verticalCenter
    * baseline, and bottom.
     
     
    Some examples:
    <syntaxhighlight lang="javascript">
    import QtQuick 1.0
    import org.kde.plasma.core 0.1 as PlasmaCore
     
     
    Item {
        width: 200
        height: 300
     
     
        Text {
            id: first
            text: i18n("1st line")
            anchors {
                top: parent.top;
                left: parent.left;
                right: parent.right;
            }
        }
        Text {
            id: second
            text: i18n("2nd line")
            anchors {
                top: first.bottom;
                left: parent.left;
                right: parent.right;
                bottom: parent.bottom;
            }
        }
    }
    </syntaxhighlight>
     
    Keep in mind, that you can only use elements that are a parent or a sibling.
     
    Here a WRONG example ('first'' and ''second'' are no siblings):
     
    <syntaxhighlight lang="javascript">
        Text {
            id: first
            text: i18n("1st line")
        }
        Item{
            id: breakIt
            Text {
                id: second
                text: i18n("2nd line")
                anchors {
                    top: first.bottom;
                }
            }
        }
    </syntaxhighlight>
    Plasmoidviewer will show you the following explanation:
     
        file:///XXXX/contents/ui/main.qml:69:9: QML Text: Cannot anchor to an item that isn't a parent or sibling.
     
     
    More examples you will find on the  [http://qt-project.org/doc/qt-4.8/qml-anchor-layout.html Anchor-based Layout in QML from the qt-project.org].
     
    === Buttons ===
     
     
    === Animations ===


    == Package Structure ==
    == Package Structure ==


    You create a .desktop file and the .qml file. They have to be in the usual plasma package structure.
    You create a .desktop file and the .qml file. They have to be in the usual Plasma package structure:


    plasmoid-qml/metadata.desktop
    * plasmoid-qml/metadata.desktop
    plasmoid-qml/contents/ui/main.qml
    * plasmoid-qml/contents/ui/main.qml


    === <tt>metadata.desktop</tt> ===
    === <tt>metadata.desktop</tt> ===
    <code ini>
    <syntaxhighlight lang="ini">
    [Desktop Entry]
    [Desktop Entry]
    Name=Hello QML
    Name=Hello QML
    Line 33: Line 161:
    X-KDE-ServiceTypes=Plasma/Applet
    X-KDE-ServiceTypes=Plasma/Applet
    Type=Service
    Type=Service
    </code>
    </syntaxhighlight>
     
    The line below indicates the default size of the plasmoid. The applet's starting size will be this, when added to a scene:
     
    <syntaxhighlight lang="ini">
    X-Plasma-DefaultSize=200,100
    </syntaxhighlight>


    ===  <tt>main.qml</tt> ===
    ===  <tt>main.qml</tt> ===
    <code javascript>
    <syntaxhighlight lang="javascript">
    import Qt 4.7
    import QtQuick 1.0


    Text {
    Text {
         text: "Hello world!";
         text: "Hello world!";
    }
    }
    </code>
    </syntaxhighlight>


    == Installing ==
    == Installing ==
    You can install your plasmoid:
    You can install your plasmoid, though obviously this is just temporary. CMake, below, is recommended:
    <syntaxhighlight lang="bash">
    plasmapkg --install plasmoid-qml
    plasmapkg --install plasmoid-qml
    </syntaxhighlight>
    === Installation through CMake ===
    In your CMakeLists.txt:
    <syntaxhighlight lang="cmake">
    project(helloqml)
    find_package(KDE4 REQUIRED)
    include(KDE4Defaults)
    install(DIRECTORY package/
            DESTINATION ${DATA_INSTALL_DIR}/plasma/plasmoids/org.kde.plasma.applet.myapplet)
    install(FILES package/metadata.desktop
            DESTINATION ${SERVICES_INSTALL_DIR} RENAME plasma-applet-myapplet.desktop)
    </syntaxhighlight>
    Your directory structure should now be as follows:
    <syntaxhighlight lang="bash">
    myproject/CMakeLists.txt
    myproject/package/
    myproject/package/metadata.desktop
    myproject/package/contents/
    myproject/package/contents/ui/
    myproject/package/contents/ui/helloworld.qml
    </syntaxhighlight>
    (if you have a configuration file (.ui file) to load the right-click 'plasmoid settings' menu, then your structure will also have myproject/package/contents/config/config.ui, or so)


    == plasmoidviewer ==
    == plasmoidviewer ==
    Line 61: Line 227:
    and use everything up to org of that path.
    and use everything up to org of that path.


    Hovewer it's '''strongly discouraged''' to use qmlviewer to develop plasmoids, because some features won't be available there:
    Hovewer it's '''strongly discouraged''' to use qmlviewer to develop plasmoids, because '''some features won't be available there, like the following''':
    * localization with i18n()
    * localization with i18n()
    * access to the global ''plasmoid'' object
    * access to the global ''plasmoid'' object
    * device specific qml files imported with plasmapackage:// urls
    * device specific qml files imported with plasmapackage:// urls
    * bindings for qicons, KJobs and KConfig
    * bindings for qicons, KJobs, services and KConfig
    * retrieving data from a DataEngine
     
    Therefore, it is recommended to simply use '''plasmoidviewer'''
     
    = Features only available in Plasma widgets =
    In order to have a better integration with the KDE platform and to reach an higher degree of expressivity, the stock features of QML have been expanded with the following features, that strictly follow the Plasmoid JavaScript API:
     
    == Minimum size ==
    if the root object of the plasmoid has the properties minimumWidth and minimumHeight, they will be used as the minimum size for the plasmoid. If they will change during the plasmoid execution, the plasmoid minimum size will be updated accordingly.
    <syntaxhighlight lang="javascript">
    import QtQuick 1.0
     
    Text {
        property int minimumWidth: paintedWidth
        property int minimumHeight: paintedHeight
        text: "Hello world!";
    }
    </syntaxhighlight>
     
    In the above example, the minimum size is bound to the paintedWidth/paintedHeight properties of the Text element, ensuring there will always be enough room for the whole text to be displayed.
     
    == Plasmoid object ==
    Every QML plasmoid will have an object called ''plasmoid'', that will give access to the configuration, the formfactor, immutability and so on. It offers the same api as the object with the same name in the Javascript API.
     
    For specific info on this, see [http://techbase.kde.org/Development/Tutorials/Plasma/JavaScript/API-PlasmoidObject Javascript API-Plasmoid Object]
     
    == Localization ==
    It is possible to localize strings with the usual i18n(), i18nc(), i18np() global functions.
     
    == Extra types ==
    Some extra types are available from withing JavaScript, namely
     
    * KConfigGroup: it's an object with its config keys readable and writable as properties
    * QIcon: can be constructed with QIcon("fdo name") such as QIcon("konqueror")
    * KJob
    * Plasma Service api
     
    = Plasma specific imports =
    To use some Plasma specific features and to take advantage of them in order for your applet to become a true Plasma applet, it is necessary to use some particular QML imports. See [http://techbase.kde.org/Development/Tutorials/Plasma/QML/API Plasma QML API].
     
    == Extra Qt features ==
    org.kde.qtextraimports
    To use, do:
     
    <syntaxhighlight lang="javascript">
    import org.kde.qtextracomponents 0.1 as QtExtraComponents
    </syntaxhighlight>
     
    * QPixmapItem
    * QImageItem
    * QIconItem


    == Plasma Widgets in QML ==
    == Plasma Widgets in QML ==
    To use plasma widgets, you simply add an import line for them.
    To use standard plasma widgets (e.g. Plasma::LineEdit, etc.), you simply add an import line for them.
    All properties, signals and slots from ordinary Plasma widgets are available there
    All properties, signals and slots from ordinary Plasma widgets are available there.
    '''These widgets are provided as a transition tool, intended to be replaced by the Plasma version of QtComponents''', which is currently in development by a gsoc. (note that the Plasma QtComponents have nothing to do with the QtExtraComponents module described above)


    <code javascript>
    <syntaxhighlight lang="javascript">
    import Qt 4.7
    import QtQuick 1.0
    import org.kde.plasma.graphicswidgets 0.1 as PlasmaWidgets
    import org.kde.plasma.graphicswidgets 0.1 as PlasmaWidgets


    Line 84: Line 302:
         }
         }
    }
    }
    </code>
    </syntaxhighlight>
    To get a list of icons installed on system, run the command:
    $ kdialog --geticon actions

    Revision as of 12:59, 9 May 2013

    Abstract

    Writing a Plasma applet in QML is very easy, in fact, with Workspaces 4.6 and Qt 4.7 it just works.

    QML Basics

    It is recommended that you have read through the Qt QML Tutorials, as there are quite a few and they are explained thoroughly. There is also a list of all standard QML elements.

    Essentially, most of the content is the same. The exceptions to be noted are how data is gathered... since we use Data Engines, it is a bit different. Text color and font should be made to use PlasmaCore.Theme.

    See the KDE Examples repository for more KDE-related helpful resources. Also of use (which use QML and Plasma) are: Plasma Mobile, Declarative Plasmoids (playground), for WIP ports of C++ originals.

    Root Item

    The root item can be anything that inherits QGraphicsItem. For example, in this case it is QGraphicsWidget which is a plasmoid. It can also simply be an Item. I also noticed that PathView does not respond to mouse inputs automatically (so flicking doesn't work). Probably because events are being intercepted. So take note, it'll have to be e.g. an Item, for that case.

    Layouts

    Row and Column

    Coloums and Rows are very easy way to grouping items and is very simular to the "normal layout management" with QHBoxLayout and QVBoxLayout. In QML these are named:

    • Column arranges its children in a column
    • Row arranges its children in a row
    • Grid arranges its children in a grid
    • Flow arranges its children like words on a page

    They have a special property spacing(int) to define the distance in pixels between two children.

    For furture help please look at Using QML Positioner and Repeater Items from qt-project.org

    Some example:

    import QtQuick 1.0
    import org.kde.plasma.core 0.1 as PlasmaCore
    
    Item { 
            Column{
                    spacing: 10
                    Row {  
                             spacing: 5
                            Text{text: 'Local'}
                            Text { 
                                    id: local
                                    text: "XX:XX:XX"
                            }
                    }
                    Row {  
                             spacing: 5
                            Text{text: 'UTC'}
                            Text { 
                                    id: utc
                                    text: "XX:XX:XX"
                            }
                    }
            }
    }
    

    Anchors

    Anchor layouts offer a nice way of grouping UI elements nicely together. The idea is that you connect edges or corners of one element to the edge or corner of another widget. Available anchors are:

    • left
    • horizontalCenter
    • right
    • top
    • verticalCenter
    • baseline, and bottom.


    Some examples:

    import QtQuick 1.0
    import org.kde.plasma.core 0.1 as PlasmaCore
    
    
    Item {
        width: 200
        height: 300
    
    
        Text {
            id: first
            text: i18n("1st line")
            anchors { 
                top: parent.top;
                left: parent.left;
                right: parent.right;
            }
        }
        Text {
            id: second
            text: i18n("2nd line")
            anchors {
                top: first.bottom;
                left: parent.left;
                right: parent.right;
                bottom: parent.bottom;
            }
        }
    }
    

    Keep in mind, that you can only use elements that are a parent or a sibling.

    Here a WRONG example ('first and second are no siblings):

        Text {
            id: first
            text: i18n("1st line")
        }
        Item{
             id: breakIt
            Text {
                id: second
                text: i18n("2nd line")
                anchors {
                     top: first.bottom;
                }
            }
        }
    

    Plasmoidviewer will show you the following explanation:

       file:///XXXX/contents/ui/main.qml:69:9: QML Text: Cannot anchor to an item that isn't a parent or sibling.
    


    More examples you will find on the Anchor-based Layout in QML from the qt-project.org.

    Buttons

    Animations

    Package Structure

    You create a .desktop file and the .qml file. They have to be in the usual Plasma package structure:

    • plasmoid-qml/metadata.desktop
    • plasmoid-qml/contents/ui/main.qml

    metadata.desktop

    [Desktop Entry]
    Name=Hello QML
    Comment=A hello world widget in QML
    Icon=chronometer
    
    X-Plasma-API=declarativeappletscript
    X-Plasma-MainScript=ui/main.qml
    X-Plasma-DefaultSize=200,100
    
    X-KDE-PluginInfo-Author=Frederik Gladhorn
    X-KDE-PluginInfo-Email=[email protected]
    X-KDE-PluginInfo-Website=http://plasma.kde.org/
    X-KDE-PluginInfo-Category=Examples
    X-KDE-PluginInfo-Name=org.kde.hello-qml
    X-KDE-PluginInfo-Version=0.0
    
    X-KDE-PluginInfo-Depends=
    X-KDE-PluginInfo-License=GPL
    X-KDE-PluginInfo-EnabledByDefault=true
    X-KDE-ServiceTypes=Plasma/Applet
    Type=Service
    

    The line below indicates the default size of the plasmoid. The applet's starting size will be this, when added to a scene:

    X-Plasma-DefaultSize=200,100
    

    main.qml

    import QtQuick 1.0
    
    Text {
        text: "Hello world!";
    }
    

    Installing

    You can install your plasmoid, though obviously this is just temporary. CMake, below, is recommended:

    plasmapkg --install plasmoid-qml
    

    Installation through CMake

    In your CMakeLists.txt:

    project(helloqml)
    
    find_package(KDE4 REQUIRED)
    
    include(KDE4Defaults)
    
    install(DIRECTORY package/
            DESTINATION ${DATA_INSTALL_DIR}/plasma/plasmoids/org.kde.plasma.applet.myapplet)
    
    install(FILES package/metadata.desktop
            DESTINATION ${SERVICES_INSTALL_DIR} RENAME plasma-applet-myapplet.desktop)
    

    Your directory structure should now be as follows:

    myproject/CMakeLists.txt
    myproject/package/
    myproject/package/metadata.desktop
    myproject/package/contents/
    myproject/package/contents/ui/
    myproject/package/contents/ui/helloworld.qml
    

    (if you have a configuration file (.ui file) to load the right-click 'plasmoid settings' menu, then your structure will also have myproject/package/contents/config/config.ui, or so)

    plasmoidviewer

    You can run it in plasmoidviewer as usual: plasmoidviewer plasmoid-qml

    qmlviewer

    It's possible to use Plasma specific imports in qml files loaded by qmlviewer:

    qmlviewer -I /usr/lib/kde4/imports/ plasmoid-qml/contents/qml/main.qml

    Where the -I is the path to the plasma plugin for qml. Try to look for the path of /usr/lib/kde4/imports/org/kde/plasma/graphicswidgets/libgraphicswidgetsbindingsplugin.so and use everything up to org of that path.

    Hovewer it's strongly discouraged to use qmlviewer to develop plasmoids, because some features won't be available there, like the following:

    • localization with i18n()
    • access to the global plasmoid object
    • device specific qml files imported with plasmapackage:// urls
    • bindings for qicons, KJobs, services and KConfig
    • retrieving data from a DataEngine

    Therefore, it is recommended to simply use plasmoidviewer

    Features only available in Plasma widgets

    In order to have a better integration with the KDE platform and to reach an higher degree of expressivity, the stock features of QML have been expanded with the following features, that strictly follow the Plasmoid JavaScript API:

    Minimum size

    if the root object of the plasmoid has the properties minimumWidth and minimumHeight, they will be used as the minimum size for the plasmoid. If they will change during the plasmoid execution, the plasmoid minimum size will be updated accordingly.

    import QtQuick 1.0
    
    Text {
        property int minimumWidth: paintedWidth
        property int minimumHeight: paintedHeight
        text: "Hello world!";
    }
    

    In the above example, the minimum size is bound to the paintedWidth/paintedHeight properties of the Text element, ensuring there will always be enough room for the whole text to be displayed.

    Plasmoid object

    Every QML plasmoid will have an object called plasmoid, that will give access to the configuration, the formfactor, immutability and so on. It offers the same api as the object with the same name in the Javascript API.

    For specific info on this, see Javascript API-Plasmoid Object

    Localization

    It is possible to localize strings with the usual i18n(), i18nc(), i18np() global functions.

    Extra types

    Some extra types are available from withing JavaScript, namely

    • KConfigGroup: it's an object with its config keys readable and writable as properties
    • QIcon: can be constructed with QIcon("fdo name") such as QIcon("konqueror")
    • KJob
    • Plasma Service api

    Plasma specific imports

    To use some Plasma specific features and to take advantage of them in order for your applet to become a true Plasma applet, it is necessary to use some particular QML imports. See Plasma QML API.

    Extra Qt features

    org.kde.qtextraimports To use, do:

    import org.kde.qtextracomponents 0.1 as QtExtraComponents
    
    • QPixmapItem
    • QImageItem
    • QIconItem

    Plasma Widgets in QML

    To use standard plasma widgets (e.g. Plasma::LineEdit, etc.), you simply add an import line for them. All properties, signals and slots from ordinary Plasma widgets are available there. These widgets are provided as a transition tool, intended to be replaced by the Plasma version of QtComponents, which is currently in development by a gsoc. (note that the Plasma QtComponents have nothing to do with the QtExtraComponents module described above)

    import QtQuick 1.0
    import org.kde.plasma.graphicswidgets 0.1 as PlasmaWidgets
    
    Item {
        width: 64
        height: 64
        PlasmaWidgets.IconWidget {
            id: icon
            Component.onCompleted: setIcon("flag-red")
            anchors.centerIn: parent
        }
    }
    

    To get a list of icons installed on system, run the command:

    $ kdialog --geticon actions