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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. For an example of how to debug Qt Quick Projects, see \l{Debugging a Qt Quick Example Application}. \section1 Setting Up QML Debugging The process of setting up debugging for Qt Quick projects depends on the \l{Creating Qt Quick Projects}{type of the project}: Qt Quick UI or Qt Quick Application, and the Qt version used. 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 For Qt 4.7, compile the QML Inspector debugging helper. For more information, see \l{Debugging Helpers for QML}. \endlist To debug Qt Quick Applications: \list 1 \o Debugging is enabled by default for Qt 4.8, or later. For Qt 4.7, select \gui Projects, and then select the \gui {Enable QML debugging} check box in the \gui qmake section 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. \o To debug applications on devices, check that Qt 4.7.4, or later, libraries are installed on the device and \l{Running on Multiple Targets}{select the device as the target} before you start debugging. \endlist \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}. \image qtquick-debugging-settings.png \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 Execute JavaScript expressions to get information about the state of the application \o Change QML code and immediately see the changes at runtime \o Inspect QML code and change it at runtime without changing the code \o Debug animations \endlist To debug already running applications: \list 1 \o Start the application. \o Select \gui {Debug > Start Debugging > Attach to QML Port}. When debugging on the desktop, you can use the default values for the connection. When debugging on devices, enter the device IP address in the \gui Host field. \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 by: \list \o \l{Setting Breakpoints}{Setting breakpoints} \o \l{Viewing Call Stack Trace}{Viewing call stack trace} \o \l{Locals and Expressions}{Viewing 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. You can change property values temporarily, without editing the source, and view the results in the running application. You can change the property values permanently in the code editor. \section1 Applying QML Changes at Runtime If you change property values or add properties in the code editor, the debugger can update the properties in the running application when you save the file. This is enabled by default. To disable it, click \inlineimage qml-observer-bar-reload.png "Apply Changes on Save button" on the toolbar. When you change property values in the \gui {QML Script Console} or \gui {QML Inspector}, they are immediately updated in the running application, but not in the source code. \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" To keep the application visible while you interact with the inspector, click \inlineimage qml-inspector-app-on-top.png (\gui {Show Application on Top}). To display a QML element in the \gui {QML Inspector} view: \list \o Select the element in the code editor. \o Click \inlineimage qml-inspector-select-button.png (\gui Select) to activate selection mode and then click an element in the running application. \o Select a child element of an element in the menu in the \gui {QML Inspector} view: \image qtquick-example-children.png \o Select an element in the element path in the \gui {QML Inspector} view. \endlist To change property values temporarily, without editing the source, double-click them and enter the new values. You can view the results in the running application. When you select an element, the cursor moves to it in the code editor, where you can change the value permanently. \section1 Debugging Animations 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. To play and pause animations in the running application, select \inlineimage qml-inspector-play.png and \inlineimage qml-inspector-pause.png on the toolbar. To change the speed at which animations are played, click and hold down \inlineimage qml-inspector-play.png or \inlineimage qml-inspector-pause.png and select a value. */