gobject:object, common-lisp:standard-object, common-lisp:t

None

Onscreen display areas in the target window system. A gdk:window object is a usually rectangular region on the screen. It is a low-level object, used to implement high-level objects such as gtk:widget and gtk:window widgets on the GTK level. A gtk:window widget is a toplevel window, the thing a user might think of as a "window" with a titlebar and so on. A gtk:window widget may contain many gdk:window objects. For example, each gtk:button widget has a gdk:window object associated with it.

Composited Windows

Normally, the windowing system takes care of rendering the contents of a child window onto its parent window. This mechanism can be intercepted by calling the gdk:window-composited function on the child window. For a composited window it is the responsibility of the application to render the window contents at the right spot.

Offscreen Windows

Offscreen windows are more general than composited windows, since they allow not only to modify the rendering of the child window onto its parent, but also to apply coordinate transformations.

To integrate an offscreen window into a window hierarchy, one has to call the gdk:offscreen-window-embedder function and handle a number of signals. The "pick-embedded-child" signal on the embedder window is used to select an offscreen child at given coordinates, and the "to-embedder" and "from-embedder" signals on the offscreen window are used to translate coordinates between the embedder and the offscreen window.

For rendering an offscreen window onto its embedder, the contents of the offscreen window are available as a surface, via the gdk:offscreen-window-surface function.

The "create-surface" signal

lambda (window width height)    :run-last      

The signal is emitted when an offscreen window needs its surface (re)created, which happens either when the the window is first drawn to, or when the window is being resized. The first signal handler that returns a non-nil surface will stop any further signal emission, and its surface will be used. Note that it is not possible to access the window's previous surface from within any callback of this signal. Calling the gdk:offscreen-window-surface function will lead to a crash.

window

The gdk:window offscreen window on which the signal is emitted.

width

An integer with the width of the offscreen surface to create.

height

An integer with the height of the offscreen surface to create.

Returns

The newly created cairo:surface-t instance for the offscreen window.

The "from-embedder" signal

lambda (window xembedder yembedder xoffscreen yoffscreen)    :run-last      

The signal is emitted to translate coordinates in the embedder of an offscreen window to the offscreen window. See also the "to-embedder" signal.

window

The gdk:window offscreen window on which the signal is emitted.

xembedder

An double float with the x coordinate in the embedder window.

yembedder

An double float with the y coordinate in the embedder window.

xoffscreen

A double float return location for the x coordinate in the offscreen window.

yoffscreen

A double float return location for the y coordinate in the offscreen window.

The "moved-to-rect" signal

lambda (window flipped final xflipped yflipped)    :run-first      

Emitted when the position of window is finalized after being moved to a destination rectangle. window might be flipped over the destination rectangle in order to keep it on-screen, in which case xflipped and yflipped will be set to true accordingly. flipped is the ideal position of window after any possible flipping, but before any possible sliding. final is flipped, but possibly translated in the case that flipping is still ineffective in keeping window on-screen. Since 3.22

window

The gdk:window object that moved.

flipped

The position of window after any possible flipping or nil if the backend cannot obtain it.

final

The final position of window or nil if the backend cannot obtain it.

xflipped

True if the anchors were flipped horizontally.

yflipped

True if the anchors were flipped vertically.

The "pick-embedded-child" signal

lambda (window x y)    :run-last      

The signal is emitted to find an embedded child at the given position.

window

The gdk:window object on which the signal is emitted.

x

A double float with the x coordinate in the window.

y

A double float with the y coordinate in the window.

Returns

The gdk:window object of the embedded child at x, y, or nil.

The "to-embedder" signal

lambda (window xoffscreen yoffscreen xembedder yembedder)    :run-last      

The signal is emitted to translate coordinates in an offscreen window to its embedder. See also the "from-embedder" signal.

window

The gdk:window object with the offscreen window on which the signal is emitted.

xoffscreen

A double float with the x coordinate in the offscreen window.

yoffscreen

A double float with the y coordinate in the offscreen window.

xembedder

A double float return location for the x coordinate in the embedder window.

yembedder

A double float return location for the y coordinate in the embedder window.