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/*!
    \contentspage {Qt Creator Manual}
    \previouspage creator-analyze-mode.html
    \page creator-qml-performance-monitor.html
    \nextpage creator-valgrind-overview.html

    \title Profiling QML Applications

    To monitor the performance of an application in the QML Profiler:

    \list 1

        \li To be able to profile an application, you must set up QML debugging
            for the project. For more information, see
            \l{Setting Up QML Debugging}.

        \li In the \gui Projects mode, select a \l{glossary-buildandrun-kit}
            {kit} with Qt version 4.7.4 or later.

            \note To profile applications on devices, you must install Qt 4.7.4
            or later libraries on them.

        \li Select \gui {Analyze > QML Profiler} to profile the current
            application.

        \li Select the
            \inlineimage qtcreator-analyze-start-button.png
            (\gui Start) button to start the application from the
            QML Profiler.

            \note If data collection does not start automatically, select the
            \inlineimage qtcreator-analyzer-button.png
            (\gui {Enable Profiling}) button.

    \endlist

    When you start analyzing an application, the application is launched, and
    the QML Profiler immediately begins to collect data. This is indicated by
    the time running in the \gui Elapsed field.

    Data is collected until you select the \gui {Enable Profiling} button. Data
    collection
    takes time, and therefore, there might be a delay
    before the data is displayed.

    Do not use application commands to exit the application, because data is
    sent to the QML Profiler when you select the \gui {Enable Profiling} button.
    The application continues to run for some seconds, after which it is stopped
    automatically. If you exit the application, the data is not sent.

    Select the \gui {Disable Profiling} button to disable the automatic
    start of the data collection when an
    application is launched. Data collection starts when you select the button
    again.

    To save all the collected data, right-click any QML Profiler view to open
    the context menu, and then select \gui {Save QML Trace}. To view the saved
    data, select \gui {Load QML Trace}. You can also deliver the saved data to
    other developers for examination or load data saved by them.

    \section1 Attaching to Running Qt Quick Applications

    To profile Qt Quick applications that are not launched by \QC, select
    \gui {Analyze > QML Profiler (External)}. You must enable QML debugging for
    the application in the project build settings. For more information, see
    \l{Setting Up QML Debugging}.

    In the \gui {QML Profiler} dialog, \gui Port field, specify the port to
    listen to.

    \section1 Analyzing Collected Data

    The \gui Timeline view displays graphical representations of:

    \list
    \if defined(enterprise)
        \li Pixmap loading times and cache sizes

        \li Scene graph events
    \endif

        \li Painting operations

        \li Compiling the QML sources

        \li Creating items using QML types

        \li Binding evaluations

        \li Signal handling

        \li Executing JavaScript behind bindings and signal handlers

        \li Summary of the recorded period

    \endlist

    \if defined(enterprise)
    Information about the pixmap cache and scene graph events are only available
    from Qt 5.1 onwards.

    \image qtcreator-qml-performance-monitor-enterprise.png "QML Profiler"
    \else
    \image qtcreator-qml-performance-monitor.png "QML Profiler"
    \endif

    Each row in the timeline (6) describes a type of QML events that were
    recorded. Move the cursor on an event on a row to see how long it takes and
    where in the source it is being called. To display the information only when
    an event is selected, disable the \gui {View Event Information on Mouseover}
    button (5).

    The outline (10) summarizes the period for which data was collected. Drag
    the zoom range (8) or click the outline to move on the outline. You can
    also move between events by selecting the \gui {Jump to Previous Event} (1)
    and \gui {Jump to Next Event} (2) buttons.

    Select the \gui {Show Zoom Slider} button (3) to open a slider that you can
    use to set the zoom level. You can also drag the zoom handles (9). To reset
    the default zoom level, right-click the timeline to open the context menu,
    and select \gui {Reset Zoom}.

    \section2 Selecting Event Ranges

    You can select an event range (7) to view the frame rate of events and to
    compare it with the frame rate of similar events. Select the
    \gui {Select Range} button (4) to activate the selection tool. Then click in
    the timeline to specify the beginning of the event range. Drag the selection
    handle to define the end of the range. The length of the range indicates the
    frame rate of the event.

    You can use event ranges also to measure delays between two subsequent
    events. Place a range between the end of the first event and the beginning
    of the second event. The \gui Duration field displays the delay between the
    events in milliseconds.

    To zoom into an event range, double-click it.

    To remove an event range, close the \gui Selection dialog.

    \section2 Evaluating Bindings

    On the \gui Binding row, you can see when a binding is evaluated and how
    long the evaluation takes. Move the mouse over the binding for details
    about the binding: location in the source code, duration, and source
    code.

    Click the binding to move the cursor in the code editor to the part of the
    code where the binding is called.

    \section2 Evaluating JavaScript Events

    On the \gui JavaScript row, you can see the time spent executing the actual
    JavaScript behind bindings and signal handlers. It lists all the JavaScript
    functions you may be using to evaluate bindings or handle signals.

    This information is displayed for applications that use the V4 engine and
    are built with Qt 5.3, or later.

    For applications that use the V8 engine and are built with Qt 5.0 or 5.1,
    you can view information about JavaScript events in the \gui JavaScript
    view.

    \section1 Viewing Events

    The \gui Events view displays the number of times each binding, create,
    compile, JavaScript, or signal event is triggered and the average time it
    takes. This allows you to examine which events you need to optimize. A high
    number of occurrences might indicate that an event is triggered
    unnecessarily. To view the median, longest, and shortest time for the
    occurrences, select \gui {Extended Event Statistics} in the context menu.

    Click on an event to move to it in the source code
    in the code editor.

    JavaScript events often duplicate bindings or signals, so you can show and
    hide them by selecting \gui {Show JavaScript Events} in the context menu.
    To show and hide QML events (\gui Create, \gui Compile, and \gui Signal),
    select \gui {Show QML Events}.

    \image qtcreator-analyzer-bindings.png "Events view"

    The \gui Callers and \gui Callees panes show dependencies between events.
    They allow you to examine the internal functions of the application.
    The \gui Callers pane summarizes the QML events that trigger a binding.
    This tells you what caused a change in a binding.
    The \gui Callees pane summarizes the QML events that a binding triggers.
    This tells you which QML events are affected if you change a binding.

    Click on an event to move to it in the source code in the code editor.

    When you select an event in the \gui Timeline view, information about it is
    displayed in the \gui Events view. To view an event range in the \gui Events
    view, select \gui {Limit Events Pane to Current Range} in the context menu
    in the \gui Timeline view.

    To copy the contents of one view or row to the clipboard, select
    \gui {Copy Table} or \gui {Copy Row} in the context menu.

    \section2 Viewing More Data

    The QML JavaScript engine optimizes trivial bindings. The QML Profiler
    does not receive information about optimized bindings, and
    therefore, it displays the text \gui {<bytecode>} and the message
    \gui {Source code not available} in the \gui Callers and \gui {Callees}
    panes.

    To inspect the optimized bindings, turn off the QML optimizer by setting the
    environment variable QML_DISABLE_OPTIMIZER to 1. To set the environment
    variable for the current project in the project settings:

    \list 1

        \li Select \gui {Projects > Run}.

        \li In \gui {Run Environment}, click \gui Add.

        \li Add the QML_DISABLE_OPTIMIZER variable and set its value to 1.

    \endlist

*/
