X11::Protocol::Ext::Composite(3pm)

Usage

 use X11::Protocol;
 my $X = X11::Protocol->new;
 $X->init_extension('Composite')
   or print "Composite extension not available";
 $X->CompositeRedirectWindow ($mywindow, 'Automatic');

Overview

The Composite extension holds the full pixel contents of windows in off-screen storage, ready for things like CopyArea(). Normally the server only keeps the visible parts of a window, not areas overlapped or obscured.

In "Automatic" mode the visible parts of a window are displayed on screen as normal. The off-screen storage is then a little like the backing store feature, but just when one or more clients declare an interest in the full content.

In "Manual" mode the window contents are not drawn on screen, only kept off-screen. This mode is for use by special "composite manager" programs which might make a composite display (hence the name of the extension) of the overlapping windows with partial-transparency or shadowing effects.

There's nothing here to draw or combine to actually make a composite window result. When required that's done with the usual core protocol drawing or with drawing extensions such as RENDER (see X11::Protocol::Ext::RENDER).

Requests

The following requests are made available with an init_extension(), as per "EXTENSIONS" in X11::Protocol.

    my $is_available = $X->init_extension('Composite');

Composite 0.1

"($server_major, $server_minor) = $X->CompositeQueryVersion ($client_major, $client_minor)"

Negotiate a protocol version with the server. $client_major and $client_minor is what the client would like, the returned $server_major and $server_minor is what the server will do, which might be less than requested (but not more than).

Actually the X.org server circa 1.10 will return a higher minor version than the client requests.

The current code supports up to 0.3 and the intention is to automatically negotiate in init_extension() if/when necessary.

"$X->CompositeRedirectWindow ($window, $update)"

"$X->CompositeRedirectSubwindows ($window, $update)"

"$X->CompositeUnredirectWindow ($window, $update)"

"$X->CompositeUnredirectSubwindows ($window, $update)"

Enable or disable a redirect of $window to off-screen storage.

Window() acts on just the given $window. Subwindows() acts on $window and also any subwindows it has now or in the future. The root window cannot be redirected.

$update is string "Automatic" or "Manual". Only one client at a time may use Manual mode on a given $window (normally a "composite manager" program).

Redirection is a per-client setting and is automatically unredirected if the client disconnects. An unredirect when not redirected is a "BadValue" error. Off-screen storage remains in effect while at least one current client has requested it.

"$X->CompositeCreateRegionFromBorderClip ($region, $window)"

Create $region (a new XID) as a server-side region object initialized to, umm, something about $window and its current border or visible parts or whatnot.

Region objects are from XFIXES 2.0 (X11::Protocol::Ext::XFIXES). CompositeCreateRegionFromBorderClip() can be used without init_extension() of XFIXES, but there's not much which can be done with a region except through XFIXES.

Composite 0.2

"$X->CompositeNameWindowPixmap ($window, $pixmap)"

Set $pixmap (a new XID) to refer to the off-screen storage of $window. $window must be viewable (mapped and all of its parents mapped) and must be redirected (by any client).

    my $pixmap = $X->new_rsrc;
    $X->CompositeNameWindowPixmap ($window, $pixmap);

$pixmap is released with FreePixmap() in the usual way. If $window or a parent is unmapped then $pixmap continues to exist, but it's association with $window is lost. If $window is mapped and redirected again later then it has a new off-screen storage and a new CompositeNameWindowPixmap() must be called to get a new pixmap for it.

Composite 0.3

"$overlay_window = $X->CompositeGetOverlayWindow ($window)"

Return the composite overlay window for the screen of $window.

This window covers the whole screen and is always above ordinary windows but below any screen saver, and doesn't appear in a QueryTree(). It's created when the first client asks for it, and shared by any further clients who ask.

"$X->CompositeReleaseOverlayWindow ($window)": Release the composite overlay window for the screen of $window. When all clients release it the overlay window is destroyed.

Home page

<http://user42.tuxfamily.org/x11-protocol-other/index.html>

Releases

7 releases since Debian 8 (Jessie); the text changed 4 times.