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111 lines
4.7 KiB
111 lines
4.7 KiB
Weston IVI-shell
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================
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Weston's IVI-shell is a highly customizable shell targeted at use cases which
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need custom control over the shell's window layout with one or more applications
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without interactive configuration of the layout by the user.
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Example use cases for the IVI-shell are IVI applications or industrial human
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machine interfaces. In general, whenever the user interface requires the exact
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positioning of multiple application surfaces on one or more screens.
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The IVI-shell also provides a means for applications to identify themselves to
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the shell by application IDs via the ivi_application Wayland protocol.
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IVI-shell client protocol
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-------------------------
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Wayland clients can implement the ``ivi_application`` Wayland protocol, which
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allows them to specify an ``ivi_id`` to allow the IVI controller to identify the
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application. This allows the controller to implement special behavior for
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well-known applications.
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The IVI-shell is able to also handle clients that use the ``xdg-shell``
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protocol, but in these cases the IVI-shell needs other means to identify client
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applications.
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See ``ivi-application.xml`` for the protocol specification.
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IVI-shell Weston modules
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------------------------
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The IVI-shell consists of two main components: The ``ivi-shell.so`` and custom
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IVI controller (with the ``hmi-controller.so`` example implementation).
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The ``ivi-shell.so`` is responsible for handling the application IDs and for
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providing abstractions to configure the window layout via the
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``ivi_layout_interface``. This interface is discussed in `IVI-shell compositor
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implementation`.
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The IVI controller uses the ``ivi_layout_interface`` to implement a window
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manager and is responsible for configuring the window layout, i.e. the position
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of the applications on the screens.
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Due to this separation, both modules must be loaded in your ``weston.ini`` to
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use the IVI-shell.
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.. code-block:: ini
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[core]
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shell=ivi-shell.so
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modules=hmi-controller.so
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If you are using your custom controller, replace ``hmi-controller.so`` with the
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name of your own controller module.
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.. figure:: images/ivi-shell.png
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:alt: IVI-shell architecture overview
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Controlling the IVI-shell
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-------------------------
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The IVI-shell provides the ``ivi_layout_interface`` API that a controller must
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use to control the window layout of the IVI-shell. See
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``ivi-shell/ivi-layout-export.h`` for the definition of this API.
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For the initial configuration, the controller has to create at least one
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``ivi_layout_layer`` and add the ``ivi_layout_layer`` to a ``weston_output``.
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The layers allow to group multiple applications surfaces and control them
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together and are the main mechanism to group and organize surfaces. These are
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always necessary to show something using the IVI-shell. The IVI-shell will
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internally create an ``ivi_layout_screen``, but a controller always uses the
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``weston_output`` directly.
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To get control over the client surfaces, the controller must use notifiers that
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trigger whenever there are changes to the client surfaces. The client surfaces
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then show up as ``ivi_layout_surface``. These have an ID, which allows the
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controller to identify the surface and reconfigure the window layout
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accordingly.
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The controller must add the ``ivi_layout_surface`` to an ``ivi_layout_layer``
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and configure it's position and z-order wrt. the other surfaces in the layer.
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Otherwise, the newly added surface will not show up on the screen.
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The IVI-shell will internally create an ``ivi_layout_view`` for each layer that
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the surface was added to. However, the views are not provided to the IVI
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controller.
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After configuring all expected changes, the controller must call the
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``commit_changes`` to atomically update the display layout.
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IVI-shell example implementation
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--------------------------------
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The IVI-shell comes with an example implementation of an IVI controller -- the
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`hmi-controller`. The hmi-controller will usually replaced by a custom
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implementation that implements the use-case-specific behavior.
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The hmi-controller is split into two parts:
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The ``hmi-controller.so`` is a Weston Plugin that uses the
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``ivi_layout_interface`` to perform the window manager tasks. It allows some
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reconfiguration of the window layout via the ``ivi_hmi_controller`` protocol.
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Other implementations may keep all window management inside the module or may
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expose even more window management via a custom protocol to an external process.
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The ``weston-ivi-shell-user-interface`` is an example hmi-controller helper
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client that serves as a user interface for controlling the hmi-controller.
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The hmi-controller can be customized using the ``[ivi-shell]`` section in the
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``weston.ini``. An example configuration will be generated in
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``<build_dir>/ivi-shell/weston.ini``.
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