DRAW-SCREEN(2)DRAW-SCREEN(2)NAME
Screen - windows and subwindows on a display
SYNOPSIS
include "draw.m";
draw := load Draw Draw->PATH;
Screen: adt
{
id: int;
image: ref Image;
fill: ref Image;
display: ref Display;
allocate: fn(image, fill: ref Image, public: int): ref Screen;
newwindow: fn(screen: self ref Screen, r: Rect,
backing:int, rgba: int): ref Image;
top: fn(screen: self ref Screen, wins: array of ref Image);
};
DESCRIPTION
A Screen is the data structure representing a set of windows visible on
a particular Image such as the display or a parent window.
id When a Screen object is allocated (see allocate below), the
system assigns it a unique integer, id. It may be declared
``public'' and accessible to arbitrary processes and machines
with access to the screen's Display. The id value may be
used as an argument to Display.publicscreen; see draw-dis‐
play(2).
fill When windows are deleted from a screen, the system uses the
fill image to repaint the screen's base image.
image The image upon which the windows appear.
display The display upon which the screen resides.
allocate(image, fill, public)
Allocate makes a new Screen object. The image argument pro‐
vides the base image on which the windows will be made. The
fill argument provides the Screen.fill image. Allocate does
not affect the contents of image; it may be necessary after
allocation to paint the base image with fill.
Using a non-zero public argument allocates a public screen;
zero requests a private screen. Public screens may be
attached by any process on any machine with access to the
Display upon which the screen is allocated, enabling remote
processes to create windows on the screen. Knowing only the
id field of the original Screen, the remote process can call
the Display.publicscreen function to acquire a handle to the
screen. The image and fill fields of a Screen obtained this
way are nil, but they are not needed for ordinary window man‐
agement.
screen.newwindow(r, backing, rgba)
Allocates a window on the display at the specified rectangle
with the background colour rgba, expressed in 32-bit RGBA
format; the return value is an Image that may be used like
any other. The backing parameter can be Draw->Refbackup,
which provides backing store to store obscured parts of the
window when necessary, and is used by the window manager and
its clients; or Draw->Refnone, which provides no refresh, and
is used for windows that are transient, or are already pro‐
tected by backing store.
screen.top(wins)
Top organizes a group of windows on a screen. Given wins, an
array of window images, it places the wins[0] element at the
top, wins[1] behind that, and so on, with the last element of
wins in front of the all the windows on the screen not in
wins. Images in the array must be on the specified screen
(nil elements are ignored).
DRAW-SCREEN(2)
