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/*!
    \page quick-states.html
    \if defined(qtdesignstudio)
    \previouspage quick-property-bindings.html
    \else
    \previouspage quick-connections-backend.html
    \endif
    \nextpage studio-3d.html

    \title Adding States

    UIs are designed to present different UI configurations in different
    scenarios, or to modify their appearances in response to user
    interaction. Often, there are a set of changes that are made concurrently,
    such that the UI could be seen to be internally changing from one
    \e state to another.

    This applies generally to UIs regardless of their complexity. A photo
    viewer may initially present images in a grid, and when an image is clicked,
    change to a detailed state where the individual image is expanded and the
    interface is changed to present new options for image editing. At the other
    end of the scale, when a button is pressed, it may change to a
    \e pressed state in which its color and position are modified so that it
    appears to be pressed down.

    Any component can change between different states to apply sets of
    changes that modify the properties of relevant components. Each state can
    present a different configuration that can, for example:

    \list
        \li Show some UI components and hide others.
        \li Present different available actions to the user.
        \li Start, stop, or pause animations.
        \li Execute some script required in the new state.
        \li Change a property value for a particular component.
        \li Show a different view.
    \endlist

    You can animate transitions between states in \l{Transition Editor}.

    \section1 Creating States

    You can create states in the \l States view, by selecting
    \uicontrol {Create New State}.

    \image qmldesigner-transitions.png "States view"

    Click the new state to switch to it in \l {Form Editor}, and then modify the
    properties of components in \l Properties.

    For example, to change the appearance of a button, you can hide the button
    image and show another image in its place. Or, to add movement to the view,
    you can change the position of a component in \uicontrol {Form Editor}
    and then add animation to the change between the states.

    The properties that you change in a state are highlighted with blue color.
    In \l{Text Editor}, you can see the changes recorded as changes
    to the base state.

    \image qmldesigner-states.png "States and Properties views"

    \note If you have \l{Locking Components}{locked a component} in
    \l Navigator, and you attempt to remove states where you change the
    values of its properties, you are prompted to confirm the removal.

    For more information, watch the following video:

    \youtube FzmLuRHQXaw

    \section1 Setting the Default State

    To determine the startup state of the application,
    select \inlineimage icons/action-icon.png
    to open the \uicontrol Actions menu, and then select
    \uicontrol {Set as Default}.

    To reset the state later, select \uicontrol Actions >
    \uicontrol {Reset Default}.

    \section1 Applying States

    To determine when a state should be applied, select \uicontrol Actions >
    \uicontrol {Set when Condition}. In \uicontrol {Binding Editor}, specify
    a \l [QtQuick]{State::when}{when} property for the state. Set the value of
    the property to a boolean expression that evaluates to \c true when you want
    the state to be applied.

    This enables you to evaluate the truthfulness of several components'
    properties and move the UI to the state in which these conditions apply.
    You can evaluate whether something is true or false, greater than or equal
    to something else, and so on. You can also use operators, such as AND or
    OR, to evaluate the truthfulness of several components.

    The when conditions are evaluated from left to right and in order of
    appearance in the code. Therefore, if you have two conditions for two
    different states that both evaluate to \c true, the first state is applied.

    In \uicontrol {Binding Editor}, select the component and property to
    create the expression. For example, to change the state when a button is
    pressed, you could select a button component and its pressed property.

    \image qtquick-states-binding-editor.png "Binding Editor in States view"

    When you compose the expressions in \uicontrol {Binding Editor}, the
    \l{Completing Code}{code completion} feature lists the components and
    their properties you can use in the expressions.

    \include creator-logical-operators.qdocinc logical operators

    \section2 Examples of when Conditions

    To apply a state to a button when the button is pressed, you could simply
    write:

    \badcode
    when: control.pressed
    \endcode

    To apply a state when the button is not pressed, select the \uicontrol NOT
    check box.

    \image qtquick-states-binding-editor-not.png "NOT check box in Binding Editor"

    To apply a state when the button is not pressed, selected, nor hovered on,
    you could combine conditions, as follows:

    \badcode
    when: !control.pressed && !control.checked && !control.hovered
    \endcode

    To apply a state when the button is pressed or selected, but not hovered on,
    you could write:

    \badcode
    when: control.pressed || control.checked && !control.hovered
    \endcode

    \section1 Using States

    To keep the code clean, you should create a base state that contains all
    the components you will need in the application. You can then create states,
    in which you hide and show a set of components and modify their properties.
    This allows you to:

    \list
        \li Align components on different views with each other.
        \li Avoid excessive property changes. If a component is invisible in
            the base state, you must define all changes to its child components
            as property changes, which leads to complicated code.
        \li Minimize the differences between the base state and the other states
            to keep the code short and readable and to improve performance.
        \li Avoid problems when using transitions and animation when changing
            states.
    \endlist

    To create views for an application by using states:

    \image qmldesigner-screen-design.png "Designing views"

    \list 1
        \li In the base state, add all components you will need in the
            application (1). While you work on one view, you can click the
            \inlineimage eye_open.png
            icon in \l Navigator to hide components on the canvas that are
            not part of a view.
        \li In \uicontrol States, select \uicontrol {Create New State} to create
            a new state and give it a name. For example, \c Normal.
        \li In \l Properties (2), deselect the \uicontrol Visibility
            check box or set \uicontrol Opacity to 0 for each component that
            is not needed in this view. If you specify the setting for the
            parent component, all child components inherit it and are also
            hidden.
        \li Create additional states for each view and set the visibility
            or opacity of the components in the view.
        \li To determine which state is applied when the application starts,
            select \uicontrol Actions > \uicontrol {Set as Default}.
    \endlist

    \if defined(qtcreator)
    \include qtquick-states-scxml.qdocinc scxml state machines
    \endif
*/
