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diff --git a/examples/wayland/qtshell/doc/src/qtshell.qdoc b/examples/wayland/qtshell/doc/src/qtshell.qdoc new file mode 100644 index 000000000..2da1c1874 --- /dev/null +++ b/examples/wayland/qtshell/doc/src/qtshell.qdoc @@ -0,0 +1,150 @@ +// Copyright (C) 2021 The Qt Company Ltd. +// SPDX-License-Identifier: LicenseRef-Qt-Commercial OR GFDL-1.3-no-invariants-only + +/*! + * \title QtShell Compositor + * \example qtshell + * \examplecategory {Embedded} + * \brief QtShell Compositor shows how to use the QtShell shell extension. + * \ingroup qtwaylandcompositor-examples + * + * QtShell Compositor is a desktop-style Wayland compositor example implementing a + * complete Qt Wayland Compositor which uses the specialized + * \l{Shell Extensions - Qt Wayland Compositor}{shell extension protocol} called \l{QtShell}. + * + * \image qtshell.jpg + * + * The compositor is implemented with Qt Quick and QML. + * + * \section1 Making the Connection + * + * The example lists QtShell as the only extension to the WaylandCompositor object. This means that + * any client connecting to the server must also support this extension, thus they should be Qt + * applications running against the same version of Qt as the compositor. + * + * \snippet qtshell/qml/main.qml shell + * + * When a client connects to the QtShell interface, it creates a \l{QtShellSurface}. The compositor + * is notified of this by the emission of the + * \l [QML] {QtShell::}{qtShellSurfaceCreated} signal. The + * example then adds the shell surface to a ListModel for easy access later. + * + * \snippet qtshell/qml/CompositorScreen.qml handleShellSurface + * + * The ListModel is used as the model for a \l{Repeater} which creates the Qt Quick items required + * to display the client contents on screen. + * + * \snippet qtshell/qml/CompositorScreen.qml repeater + * + * It uses the local \c Chrome type, which handles window states and decorations. + * + * \section1 Chrome + * + * The \c Chrome is the type that ensures the client contents are visible and also handles window + * state, position, size, and so on. It uses the built-in QtShellChrome as a basis, which + * automatically handles window state (maximized, minimized, fullscreen) and window activation + * (ensuring that only a single window is active at the time). + * + * Its behavior can be customized to some extent, but it is also possible to write the \c Chrome + * functionality from scratch, building from a basic \l{Item} type instead. QtShellChrome is a + * convenience class which provides typical compositor behavior, and saves us the time of + * implementing this logic in the example. + * + * However the \c Chrome is written, it should have a ShellSurfaceItem to hold the client contents. + * + * \snippet qtshell/qml/Chrome.qml shellsurfaceitem + * + * The ShellSurfaceItem is the visual representation of the client's contents in the Qt Quick scene. + * Its size should usually match the size of the client's buffer, otherwise it may look stretched or + * squeezed. QtShellChrome will automatically be sized to the \l{QtShellSurface}'s + * \l{QtShellSurface::windowGeometry}{windowGeometry}, which is size of the + * client's buffer plus the size of the frame margins. The frame margins are reserved areas on the + * sides of the \c Chrome which can be used to contain window decorations. + * + * The ShellSurfaceItem is therefore anchored to the window decorations to fill the area reserved + * for the client buffer. + * + * \section1 Window Decorations + * + * The window decoration is usually a frame around a client's contents which adds information + * (such as a window title) and the possibility of user interaction (such as resizing, closing, + * moving the window, and so on.) + * + * With \l{QtShell}, window decorations are always drawn by the compositor and not by the client. + * In order for sizes and positions to be communicated correctly, QtShell also needs to know how + * much of the window is reserved for these decorations. This can be handled automatically by + * QtShellChrome, or manually, by setting + * \l{QtShellChrome::frameMarginLeft}{frameMarginLeft}, + * \l{QtShellChrome::frameMarginRight}{frameMarginRight}, + * \l{QtShellChrome::frameMarginTop}{frameMarginTop} and + * \l{QtShellChrome::frameMarginBottom}{frameMarginBottom}. + * + * For typical cases where there are resize handles around the window and a title bar at the top, + * it is more convenient to rely on the default frame margins. The QtShell Compositor example + * does this. + * + * First, we create Qt Quick items to represent the different parts of the window's decorations. + * On the left side, for example, there should be a resize handle that the user can grab and drag in + * order to resize the window. + * + * \snippet qtshell/qml/Chrome.qml leftResizeHandle + * + * We simply make this a five-pixel wide rectangle in the example, anchored to the top, bottom and + * left side of the \c Chrome. + * + * Similarly, we add Qt Quick items that represent the right, top, bottom, top-left, top-right, + * bottom-left and bottom-right resize handles. We also add a title bar. When the decorations have + * been created and anchored correctly to the sides of the \c{Chrome}, we set corresponding + * properties in QtShellChrome. + * + * \snippet qtshell/qml/Chrome.qml decorations + * + * When the decoration properties are set, the default resizing and repositioning behavior will be + * added automatically. The user will be able to interact with the resize handles in order to resize + * the window, and drag the title bar to reposition it. The frame margins of the QtShellSurface will + * also be set automatically to account for the size of the decorations (as long as none of the + * frame margins properties have been set explicitly.) + * + * The visibility of the decorations will be handled automatically by the QtShellChrome based on + * the window flags of the QtShellSurface. + * + * \section1 Window Management + * + * As part of the decorations, it is common to have tool buttons which manage the window state + * and life span. In the example, these are added to the title bar. + * + * \snippet qtshell/qml/Chrome.qml buttons + * + * The visibility of each button is conditional on the window flag for that button, and when each + * of them is clicked, we simply call the corresponding method in QtShellChrome. The exception is + * the "close" button, which calls the + * \l{QtWaylandCompositor::QtShellSurface::sendClose()}{sendClose()} method in QtShellSurface. + * This instructs the client to close itself, and ensures a graceful shutdown of the application. + * + * \snippet qtshell/qml/CompositorScreen.qml taskbar + * + * As an additional window management tool, the example has a "task bar". This is just a row of + * tool buttons at the bottom with the window titles. The buttons can be clicked to de-minimize + * applications and bring them to the front if they are obscured by other windows. Similarly + * to the \c{Chrome}, we use a \l{Repeater} for creating the tool buttons and use the shell surface + * list as model for this. For simplicity, the example does not have any handling of overflow (when + * there are too many applications for the task bar), but in a proper compositor, this is also + * something that should be considered. + * + * Finally, to avoid maximized applications expanding to fill the area covered by the task bar, we + * create a special item to manage the parts of the WaylandOutput real estate that is available to + * client windows. + * + * \snippet qtshell/qml/CompositorScreen.qml usableArea + * + * It is simply anchored to the sides of the WaylandOutput, but its bottom anchor is at the top + * of the task bar. + * + * In the \c{Chrome}, we use this area to define the \l{QtShellChrome::maximizedRect}{maximizedRect} + * of the window. + * + * \snippet qtshell/qml/Chrome.qml maximizedRect + * + * By default, this property will match the full WaylandOutput. In our case, however, we do not want + * to include the task bar in the available area, so we override the default. + */ |