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NAME
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Screen, allocscreen, publicscreen, freescreen, allocwindow, bottomwindow,
bottomnwindows, topwindow, topnwindows, originwindow – window management
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SYNOPSIS
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#include <u.h>
#include <libc.h>
#include <draw.h>
typedef
struct Screen
{
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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 */
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} 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, int val)
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
{
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/* refresh methods */
Refbackup= 0,
Refnone= 1,
Refmesg= 2
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};
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DESCRIPTION
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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 val 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(3)). 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(3)),
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).
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EXAMPLES
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To move a window to the upper left corner of the display,
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originwindow(w, w−>r.min, Pt(0, 0));
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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,
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originwindow(w, Pt(0, 0), w−>r.min);
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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.
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SOURCE
SEE ALSO
BUGS
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The refresh method Refmesg should be finished.
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