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44 lines
1.8 KiB
44 lines
1.8 KiB
.. _libweston-head:
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Heads
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=====
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A head is represented by a :type:`weston_head` object.
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A head refers to a monitor when driving hardware, but it can also be a window
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in another window system, or a virtual concept. Essentially a head is a place
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where you could present an image. The image will be produced by a weston_output
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where the head is attached to.
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In display hardware, a head represents a display connector in a computer
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system, not the actual monitor connected to the connector. A head carries
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monitor information, if present, like make and model, EDID and possible video
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modes. Other properties are DPMS mode and backlight control.
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In terms of Wayland protocol, a head corresponds to a wl_output. If one
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:type:`weston_output` has several heads, meaning that the heads are cloned,
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each head is represented as a separate wl_output global in wl_registry. Only
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the heads of an enabled output are exposed as wl_outputs.
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Heads can appear and disappear dynamically, mainly because of DisplayPort
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Multi-Stream Transport where connecting a new monitor may expose new
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connectors. Window and virtual outputs are often dynamic as well.
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Heads are always owned by libweston which dictates their lifetimes. Some
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backends may offer specific API to create and destroy heads, but hardware
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backends like DRM-backend create and destroy heads on their own.
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.. note::
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:func:`weston_head_init` and :func:`weston_head_release` belong to the
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private/internal backend API and should be moved accordingly once that
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section has been created. There are many other functions as well that are
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intended only for backends.
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A :type:`weston_head` must be attached/detached from a :type:`weston_output`.
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To that purpose you can use :func:`weston_output_attach_head`, respectively
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:func:`weston_head_detach`.
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.. doxygengroup:: head
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:content-only:
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