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Debugging projects not created with the Qt Quick wizards is only supported with Qt 4.8, or later. To debug Qt Quick applications running on devices, you must install Qt 4.7.4, or later, libraries on devices. To debug applications on Symbian devices, you must install also QML Viewer on them. \section1 Setting Up QML Debugging The process of setting up debugging for Qt Quick projects depends on the type of the project: Qt Quick UI or Qt Quick Application. To debug Qt Quick UI projects: \list 1 \o Select \gui Projects, and then select the \gui QML check box in the \gui {Run Settings}, to enable QML debugging. \o Compile the QML Inspector debugging helper. For more information, see \l{Debugging Helpers for QML}. \endlist To debug Qt Quick Applications: \list 1 \o Select \gui Projects, and then select the \gui {Link QML debugging library} check box in \gui {Build Steps}. You might have to compile the library first, by selecting the \gui Compile link. \image qml-link-debugging-library.png "Build Steps" \note Debugging requires opening a socket at a well-known port, which presents a security risk. Anyone on the Internet could connect to the application that you are debugging and execute any JavaScript functions. Therefore, you must make sure that the port is properly protected by a firewall. \o In the \gui {Run Settings}, select the \gui QML check box to enable QML debugging. \o Select \gui {Build > Rebuild Project} to clean and rebuild the project. \endlist To debug Qt Quick Applications on devices, install Qt 4.7.4, or later, libraries on devices. Then select the device as the target before you start debugging. \section1 Mixed C++/QML Debugging To debug both the C++ and QML parts of your application at the same time, select the checkboxes for both languages in the \gui{Run Settings}. However, C++ breakpoints are be ignored until the debugger attaches also to the QML engine. \section1 Starting QML Debugging To start the application, choose \gui {Debug > Start Debugging > Start Debugging} or press \key F5. Once the application starts running, it behaves and performs as usual. You can then perform the following tasks: \list \o Debug JavaScript functions \o Preview QML changes at runtime \o Inspect QML at runtime \endlist \section1 Debugging JavaScript Functions You can use the \QC \gui Debug mode to inspect the state of your application while debugging. You can interact with the debugger in several ways, as described in the following sections: \list \o \l{Setting Breakpoints} \o \l{Viewing Call Stack Trace} \o \l{Locals and Expressions} \endlist \section1 Executing JavaScript Expressions When the application is interrupted by a breakpoint, you can use the \gui {QML Script Console} to execute JavaScript expressions in the current context. To open it, choose \gui {Window > View > QML Script Console}. \image qml-script-console.png "QML Script Console view" You can type JavaScript expressions and use them to get information about the state or your application. For example, property values. You can see the current value of a property by hovering over it in the code editor. \section1 Applying QML Changes at Runtime If you change property values or add properties in the code editor, the changes are updated in the running application when you save them. If live preview is not supported for an element, a message appears. Click \gui Reload to preview the changes. Reloading is enabled by default. To disable it, click \inlineimage qml-observer-bar-reload.png "Apply Changes on Save button" on the toolbar. \section1 Inspecting QML at Runtime While the application is running, you can use the \gui {QML Inspector} view to explore the object structure, debug animations, and inspect colors. To open the \gui {QML Inspector} view, choose \gui {Window > View > QML Inspector}. The view shows the properties of the currently selected QML element. \image qml-observer-view.png "QML Inspector view" When you debug complex applications, you can use the inspection mode to jump to the position in code where an element is defined. You are switched to the inspection mode, when you click the \gui Select, \gui Zoom, or \gui {Color Picker} button on the toolbar. \image qml-observer-buttons.png "QML Inspector toolbar" When the \gui Select tool is enabled, you can click elements in the running application to jump to their definitions in the code. The properties of the selected element are displayed in the \gui {QML Inspector} view. The element hierarchy is displayed as a bread crumb path. You can also right-click an element in the running application to view the element hierarchy as a context menu. \image qml-observer-context-menu.png "QML Inspector" To switch to the zoom mode, click the \gui Zoom button. Click in the running application to zoom in. Right-click to open a context menu that contains zoom controls. To inspect colors, click the \gui {Color Picker} button. You can also click \inlineimage qml-observer-bar-copy-color.png "Copy Color button" to copy the color definition to the clipboard. To switch out of the inspection mode, deselect the \gui Select, \gui Zoom, and \gui {Color Picker} button. To move the application running in \QQV to the front, select the \gui {Show Application on Top} button. \section1 Debugging Animations \image qml-observer.png To play and pause animations in the running application, select the \gui {Play/Pause Animations} button on the toolbar or \gui {Debugging > Animations > Pause}, or press \key {Ctrl+.}. To change the speed at which animations are played, select a value in \gui {Debugging > Animations} or click and hold down the \gui {Play/Pause Animations} button to select a value. */