WINDOW(2)WINDOW(2)
NAME
Screen, allocscreen, publicscreen, freescreen, allocwindow, bottomwindow, bottomnwindows, topwindow, topnwindows, originwindow – window management
SYNOPSIS
#include <u.h>
#include <libc.h>
#include <draw.h>
typedef
struct Screen
{
Display *display; /* display holding data */
int id; /* id of system-held Screen */
Image *image; /* unused; for reference only */
Image *fill; /* color to paint behind windows */
} Screen;
Screen* allocscreen(Image *image, Image *fill, int public)
Screen* publicscreen(Display *d, int id, ulong chan)
int freescreen(Screen *s)
Image* allocwindow(Screen *s, Rectangle r, int ref, ulong col)
void bottomwindow(Image *w)
void bottomnwindows(Image **wp, int nw)
void topwindow(Image *w)
void topnwindows(Image **wp, int nw)
int originwindow(Image *w, Point log, Point scr)
enum
{
/* refresh methods */
Refbackup = 0,
Refnone = 1,
Refmesg = 2
};
DESCRIPTION
Windows are represented as
Images
and may be treated as regular images for all drawing operations.
The routines discussed here permit the creation, deletion, and shuffling
of windows, facilities that do not apply to regular images.
To create windows, it is first necessary to allocate a
Screen
data structure to gather them together.
A
Screen
turns an arbitrary image into something that may have windows upon it.
It is created by
allocscreen,
which takes an
image
upon which to place the windows (typically
display->image),
a
fill
image to paint the background behind all the windows on the image,
and a flag specifying whether the result should be publicly visible.
If it is public, an arbitrary other program connected to the same
display may acquire a pointer to the same screen by calling
publicscreen
with the
Display
pointer and the
id
of the published
Screen,
as well as the expected channel descriptor, as a safety check.
It will usually require some out-of-band coordination for programs to share a screen profitably.
Freescreen
releases a
Screen,
although it may not actually disappear from view until all the windows upon it have also been deallocated.
Unlike
allocwindow,
allocscreen
does
not
initialize the appearance of the
Screen.
Windows are created by
allocwindow,
which takes a pointer to the
Screen
upon which to create the window, a rectangle
r
defining its geometry, an integer pixel value
col
to color the window initially, and a refresh method
ref.
The refresh methods are
Refbackup,
which provides backing store and is the method used by
rio(1)
for its clients;
Refnone,
which provides no refresh and is designed for temporary uses
such as sweeping a display rectangle, for windows that are
completely covered by other windows, and for windows that
are already protected by backing store; and
Refmesg,
which causes messages to be delivered to the owner of the window
when it needs to be repainted.
Refmesg
is not fully implemented.
The result of
allocwindow
is an
Image
pointer that may be treated like any other image.
In particular, it is freed by calling
freeimage
(see
allocimage(2)).
The following functions, however, apply only to windows, not regular images.
Bottomwindow
pushes window
w
to the bottom of the stack of windows on its
Screen,
perhaps obscuring it.
Topwindow
pulls window
w
to the top, making it fully visible on its
Screen.
(This
Screen
may itself be within a window that is not fully visible;
topwindow
will not affect the stacking of this parent window.)
Bottomnwindows
and
Topnwindows
are analogous, but push or pull a group of
nw
windows listed in the array
wp.
The order within
wp
is unaffected.
Each window is created as an
Image
whose
Rectangle
r
corresponds to the rectangle given to
allocwindow
when it was created. Thus, a newly created window
w
resides on its
Screen->image
at
w->r
and has internal coordinates
w->r.
Both these may be changed by a call to
originwindow.
The two
Point
arguments to
originwindow
define the upper left corner of the logical coordinate system
(log)
and screen position
(scr).
Their usage is shown in the Examples section.
Rio(1)
creates its client windows with backing store,
Refbackup.
The graphics initialization routine,
initdraw
(see
graphics(2)),
builds a
Screen
upon this, and then allocates upon that another window indented
to protect the border. That window is created
Refnone,
since the backing store created by
rio
protects its contents. That window is the one known in the
library by the global name
screen
(a historic but confusing choice).
EXAMPLES
To move a window to the upper left corner of the display,
originwindow(w, w->r.min, Pt(0, 0));
To leave a window where it is on the screen but change its internal
coordinate system so (0, 0) is the upper left corner of the window,
originwindow(w, Pt(0, 0), w->r.min);
After this is done,
w->r
is translated to the origin and there will be no way to discover the
actual screen position of the window unless it is recorded separately.
SOURCE
/sys/src/libdraw
SEE
graphics(2),
draw(2),
cachechars(2),
draw(3)
BUGS
The refresh method
Refmesg
should be finished.