














		  X Nonrectangular Window

		  Shape Extension Protocol



			Version 1.0
		   X Consortium Standard
		 X Version 11, Release 6.4






		       Keith Packard
		      MIT X Consortium









Copyright (C) 1989 X Consortium

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1.  Overview

This extension provides arbitrary window and border shapes
within the X11 protocol.

The restriction of rectangular windows within the X protocol
is a significant limitation in the implementation of many
styles of user interface.  For example, many transient win-
dows would like to display a ``drop shadow'' to give the
illusion of 3 dimensions.  As another example, some user
interface style guides call for buttons with rounded cor-
ners; the full simulation of a nonrectangular shape, partic-
ularly with respect to event distribution and cursor shape,
is not possible within the core X protocol.  As a final
example, round clocks and nonrectangular icons are desirable
visual addition to the desktop.

This extension provides mechanisms for changing the visible
shape of a window to an arbitrary, possibly disjoint, non-
rectangular form.  The intent of the extension is to supple-
ment the existing semantics, not replace them.	In particu-
lar, it is desirable for clients that are unaware of the
extension to still be able to cope reasonably with shaped
windows.  For example, window managers should still be able
to negotiate screen real estate in rectangular pieces.
Toward this end, any shape specified for a window is clipped
by the bounding rectangle for the window as specified by the
window's geometry in the core protocol.  An expected conven-
tion would be that client programs expand their shape to
fill the area offered by the window manager.

2.  Description

Each window (even with no shapes specified) is defined by
two regions:  the bounding region and the clip region.	The
bounding region is the area of the parent window that the
window will occupy (including border). The clip region is
the subset of the bounding region that is available for sub-
windows and graphics.  The area between the bounding region
and the clip region is defined to be the border of the win-
dow.

A nonshaped window will have a bounding region that is a
rectangle spanning the window, including its border; the
clip region will be a rectangle filling the inside dimen-
sions (not including the border).  In this document, these
areas are referred to as the default bounding region and the
default clip region.  For a window with inside size of width
by height and border width bwidth, the default bounding and
clip regions are the rectangles (relative to the window ori-
gin):






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     X11 Nonrectangular Window Shape Extension Protocol

__
|
bounding.x = -bwidth
bounding.y = -bwidth
bounding.width = width + 2 * bwidth
bounding.height = height + 2 * bwidth

clip.x = 0
clip.y = 0
clip.width = width
clip.height = height

|__

This extension allows a client to modify either or both of
the bounding or clip regions by specifying new regions that
combine with the default regions.  These new regions are
called the client bounding region and the client clip
region.  They are specified relative to the origin of the
window and are always defined by offsets relative to the
window origin (that is, region adjustments are not required
when the window is moved).  Three mechanisms for specifying
regions are provided:  a list of rectangles, a bitmap, and
an existing bounding or clip region from a window.  This is
modeled on the specification of regions in graphics contexts
in the core protocol and allows a variety of different uses
of the extension.

When using an existing window shape as an operand in speci-
fying a new shape, the client region is used, unless none
has been set, in which case the default region is used
instead.

The effective bounding region of a window is defined to be
the intersection of the client bounding region with the
default bounding region.  Any portion of the client bounding
region that is not included in the default bounding region
will not be included in the effective bounding region on the
screen.  This means that window managers (or other geometry
managers) used to dealing with rectangular client windows
will be able to constrain the client to a rectangular area
of the screen.

Construction of the effective bounding region is dynamic;
the client bounding region is not mutated to obtain the
effective bounding region.  If a client bounding region is
specified that extends beyond the current default bounding
region, and the window is later enlarged, the effective
bounding region will be enlarged to include more of the
client bounding region.

The effective clip region of a window is defined to be the
intersection of the client clip region with both the default
clip region and the client bounding region.  Any portion of
the client clip region that is not included in both the



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     X11 Nonrectangular Window Shape Extension Protocol


default clip region and the client bounding region will not
be included in the effective clip region on the screen.

Construction of the effective clip region is dynamic; the
client clip region is not mutated to obtain the effective
clip region.  If a client clip region is specified that
extends beyond the current default clip region and the win-
dow or its bounding region is later enlarged, the effective
clip region will be enlarged to include more of the client
clip region if it is included in the effective bounding
region.

The border of a window is defined to be the difference
between the effective bounding region and the effective clip
region.  If this region is empty, no border is displayed.
If this region is nonempty, the border is filled using the
border-tile or border-pixel of the window as specified in
the core protocol.  Note that a window with a nonzero border
width will never be able to draw beyond the default clip
region of the window.  Also note that a zero border width
does not prevent a window from having a border, since the
clip shape can still be made smaller than the bounding
shape.

All output to the window and visible regions of any subwin-
dows will be clipped to the effective clip region.  The
server must not retain window contents beyond the effective
bounding region with backing store.  The window's origin
(for graphics operations, background tiling, and subwindow
placement) is not affected by the existence of a bounding
region or clip region.

Areas that are inside the default bounding region but out-
side the effective bounding region are not part of the win-
dow; these areas of the screen will be occupied by other
windows.  Input events that occur within the default bound-
ing region but outside the effective bounding region will be
delivered as if the window was not occluding the event posi-
tion.  Events that occur in a nonrectangular border of a
window will be delivered to that window, just as for events
that occur in a normal rectangular border.

An InputOnly window can have its bounding region set, but it
is a Match error to attempt to set a clip region on an Inpu-
tOnly window or to specify its clip region as a source to a
request in this extension.

The server must accept changes to the clip region of a root
window, but the server is permitted to ignore requested
changes to the bounding region of a root window.  If the
server accepts bounding region changes, the contents of the
screen outside the bounding region are implementation depen-
dent.




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     X11 Nonrectangular Window Shape Extension Protocol


3.  Types

The following types are used in the request and event defi-
nitions in subsequent sections.

SHAPE_KIND: {Bounding, Clip}

SHAPE_OP: {Set, Union, Intersect, Subtract, Invert}

Set indicates that the region specified as an explicit
source in the request is stored unaltered as the new desti-
nation client region.  Union indicates that the source and
destination regions are unioned together to produce the new
destination client region.  Intersect indicates that the
source and destination regions are intersected together to
produce the new destination client region.  Subtract indi-
cates that the source region is subtracted from the destina-
tion region to produce the new destination region.  Invert
indicates that the destination region is subtracted from the
source region to produce the new destination region.

4.  Requests

__
|    ShapeQueryVersion

   =>

     majorVersion: CARD16
     minorVersion: CARD16
|__

This request can be used to ensure that the server version
of the SHAPE extension is usable by the client.  This docu-
ment defines major version one (1), minor version zero (0).

__
|    ShapeRectangles

     dest: WINDOW
     destKind: SHAPE_KIND
     op: SHAPE_OP
     xOff, yOff: INT16
     rectangles: LISTofRECTANGLES
     ordering: {UnSorted, YSorted, YXSorted, YXBanded}

     Errors: Window, Length, Match, Value
|__

This request specifies an array of rectangles, relative to
the origin of the window plus the specified offset (xOff and
yOff) that together define a region.  This region is com-
bined (as specified by the operator op) with the existing
client region (specified by destKind) of the destination



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     X11 Nonrectangular Window Shape Extension Protocol


window, and the result is stored as the specified client
region of the destination window.  Note that the list of
rectangles can be empty, specifying an empty region; this is
not the same as passing None to ShapeMask.

If known by the client, ordering relations on the rectangles
can be specified with the ordering argument.  This may pro-
vide faster operation by the server.  The meanings of the
ordering values are the same as in the core protocol Set-
ClipRectangles request.  If an incorrect ordering is speci-
fied, the server may generate a Match error, but it is not
required to do so.  If no error is generated, the graphics
results are undefined.	Except for UnSorted, the rectangles
should be nonintersecting, or the resulting region will be
undefined.  UnSorted means that the rectangles are in arbi-
trary order.  YSorted means that the rectangles are nonde-
creasing in their Y origin.  YXSorted additionally con-
strains YSorted order in that all rectangles with an equal Y
origin are nondecreasing in their X origin.  YXBanded addi-
tionally constrains YXSorted by requiring that, for every
possible Y scanline, all rectangles that include that scan-
line have identical Y origins and Y extents.

__
|    ShapeMask

     dest: WINDOW
     destKind: SHAPE_KIND
     op: SHAPE_OP
     xOff, yOff: INT16
     source: PIXMAP or None

     Errors: Window, Pixmap, Match, Value
|__

The source in this request is a 1-bit deep pixmap, or None.
If source is None, the specified client region is removed
from the window, causing the effective region to revert to
the default region.  The ShapeNotify event generated by this
request and subsequent ShapeQueryExtents will report that a
client shape has not been specified.  If a valid pixmap is
specified, it is converted to a region, with bits set to one
included in the region and bits set to zero excluded, and an
offset from the window origin as specified by xOff and yOff.
The resulting region is then combined (as specified by the
operator op) with the existing client region (indicated by
destKind) of the destination window, and the result is
stored as the specified client region of the destination
window.  The source pixmap and destination window must have
been created on the same screen, or else a Match error
results.






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     X11 Nonrectangular Window Shape Extension Protocol

__
|    ShapeCombine

     dest: WINDOW
     destKind: SHAPE_KIND
     op: SHAPE_OP
     xOff, yOff: INT16
     source: WINDOW
     sourceKind: SHAPE_KIND

     Errors: Window, Match, Value
|__

The client region, indicated by sourceKind, of the source
window is offset from the window origin by xOff and yOff and
combined with the client region, indicated by destKind, of
the destination window.  The result is stored as the speci-
fied client region of the destination window.  The source
and destination windows must be on the same screen, or else
a Match error results.

__
|    ShapeOffset

     dest: WINDOW
     destKind: SHAPE_KIND
     xOff, yOff: INT16

     Errors: Window, Match, Value
|__

The client region, indicated by destKind, is moved relative
to its current position by the amounts xOff and yOff.

























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     X11 Nonrectangular Window Shape Extension Protocol

__
|    ShapeQueryExtents

     dest: WINDOW

   =>

     boundingShaped: BOOL
     clipShaped: BOOL
     xBoundingShape: INT16
     yBoundingShape: INT16
     widthBoundingShape: CARD16
     heightBoundingShape: CARD16
     xClipShape: INT16
     yClipShape: INT16
     widthClipShape: CARD16
     heightClipShape: CARD16

     Errors: Window
|__

The boundingShaped and clipShaped results are True if the
corresponding client regions have been specified, else they
are False.  The x, y, width, and height values define the
extents of the client regions, when a client region has not
been specified, the extents of the corresponding default
region are reported.

__
|    ShapeSelectInput

     window: WINDOW
     enable: BOOL

     Errors: Window, Value
|__

Specifying enable as True causes the server to send the
requesting client a ShapeNotify event whenever the bounding
or clip region of the specified window is altered by any
client.  Specifying enable as False causes the server to
stop sending such events.
















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     X11 Nonrectangular Window Shape Extension Protocol

__
|    ShapeInputSelected

     window: WINDOW

   =>

     enable: BOOL

     Errors: Window
|__

If enable is True, then ShapeNotify events for the window
are generated for this client.

__
|    ShapeGetRectangles

     window: WINDOW
     kind: SHAPE_KIND

   =>

     rectangles: LISTofRECTANGLE
     ordering: {UnSorted, YSorted, YXSorted, YXBanded}

     Errors: Window, Match
|__

A list of rectangles describing the region indicated by
kind, and the ordering of those rectangles, is returned.
The meaning of the ordering values is the same as in the
ShapeRectangles request.

5.  Events

__
|    ShapeNotify

     window: WINDOW
     kind: SHAPE_KIND
     shaped: BOOL
     x, y: INT16
     width, height: CARD16
     time: TIMESTAMP
|__

Whenever the client bounding or clip shape of a window is
modified, a ShapeNotify event is sent to each client that
has used ShapeSelectInput to request it.

Kind indicates which client region (bounding or clip) has
been modified; shaped is True when the window has a client
shape of type kind, and is False when the window no longer
has a client shape of this type.  The x, y, width, and



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     X11 Nonrectangular Window Shape Extension Protocol


height indicate the extents of the current shape.  When
shaped is False these will indicate the extents of the
default region.  The timestamp indicates the server time
when the shape was changed.

6.  Encoding

Please refer to the X11 Protocol Encoding document as this
document uses conventions established there.

The name of this extension is ``SHAPE''.


6.1.  New Types


SHAPE_KIND
       0	 Bounding
       1	 Clip



SHAPE_OP
       0	 Set
       1	 Union
       2	 Intersect
       3	 Subtract
       4	 Invert


6.2.  Requests


ShapeQueryVersion
  1  CARD8		 opcode
  1  0			 shape opcode
  2  1			 request length


 =>
  1  1			 Reply
  1			 unused
  2  CARD16		 sequence number
  4  0			 length
  2  CARD16		 major version
  2  CARD16		 minor version
  20			 unused



ShapeRectangles
  1  CARD8		 opcode
  1  1			 shape opcode
  2  4+2n		 request length



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     X11 Nonrectangular Window Shape Extension Protocol


  1  SHAPE_OP		 operation
  1  SHAPE_KIND 	 destination kind
  1			 ordering
     0	       UnSorted
     1	       YSorted
     2	       YXSorted
     3	       YXBanded
  1			 unused
  4  WINDOW		 destination window
  2  INT16		 x offset
  2  INT16		 y offset
  8n LISTofRECTANGLE	 rectangles



ShapeMask
  1  CARD8		 opcode
  1  2			 shape opcode
  2  5			 request length
  1  SHAPE_OP		 operation
  1  SHAPE_KIND 	 destination kind
  2			 unused
  4  WINDOW		 destination window
  2  INT16		 x offset
  2  INT16		 y offset
  4  PIXMAP		 source bitmap
     0	       None



ShapeCombine
  1  CARD8		 opcode
  1  3			 shape opcode
  2  5			 request length
  1  SHAPE_OP		 operation
  1  SHAPE_KIND 	 destination kind
  1  SHAPE_KIND 	 source kind
  1			 unused
  4  WINDOW		 destination window
  2  INT16		 x offset
  2  INT16		 y offset
  4  WINDOW		 source window



ShapeOffset
  1  CARD8		 opcode
  1  4			 shape opcode
  2  4			 request length
  1  SHAPE_KIND 	 destination kind
  3			 unused
  4  WINDOW		 destination window
  2  INT16		 x offset
  2  INT16		 y offset



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     X11 Nonrectangular Window Shape Extension Protocol


ShapeQueryExtents
  1  CARD8		 opcode
  1  5			 shape opcode
  2  2			 request length
  4  WINDOW		 destination window


 =>
  1  1			 Reply
  1			 unused
  2  CARD16		 sequence number
  4  0			 reply length
  1  BOOL		 bounding shaped
  1  BOOL		 clip shaped
  2			 unused
  2  INT16		 bounding shape extents x
  2  INT16		 bounding shape extents y
  2  CARD16		 bounding shape extents width
  2  CARD16		 bounding shape extents height
  2  INT16		 clip shape extents x
  2  INT16		 clip shape extents y
  2  CARD16		 clip shape extents width
  2  CARD16		 clip shape extents height
  4			 unused



ShapeSelectInput
  1  CARD8		 opcode
  1  6			 shape opcode
  2  3			 request length
  4  WINDOW		 destination window
  1  BOOL		 enable
  3			 unused



ShapeInputSelected
  1  CARD8		 opcode
  1  6			 shape opcode
  2  2			 request length
  4  WINDOW		 destination window


 =>
  1  1			 Reply
  1  BOOL		 enabled
  2  CARD16		 sequence number
  4  0			 reply length
  24			 unused



ShapeGetRectangles



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     X11 Nonrectangular Window Shape Extension Protocol


  1  CARD8		 opcode
  1  7			 shape opcode
  2  3			 request length
  4  WINDOW		 window
  1  SHAPE_KIND 	 source kind
  3			 unused


 =>
  1  1			 Reply
  1			 ordering
     0	       UnSorted
     1	       YSorted
     2	       YXSorted
     3	       YXBanded
  2  CARD16		 sequence number
  4  2n 		 reply length
  4  CARD32		 nrects
  20			 unused
  8n LISTofRECTANGLE	 rectangles


6.3.  Events



ShapeNotify
  1  CARD8		 type (0 + extension event base)
  1  SHAPE_KIND 	 shape kind
  2  CARD16		 sequence number
  4  WINDOW		 affected window
  2  INT16		 x value of extents
  2  INT16		 y value of extents
  2  CARD16		 width of extents
  2  CARD16		 height of extents
  4  TIMESTAMP		 server time
  1  BOOL		 shaped
  11			 unused


7.  Glossary

bounding region

     The area of the parent window that this window will
     occupy.  This area is divided into two parts:  the bor-
     der and the interior.










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     X11 Nonrectangular Window Shape Extension Protocol


clip region

     The interior of the window, as a subset of the bounding
     region.  This region describes the area that will be
     painted with the window background when the window is
     cleared, will contain all graphics output to the win-
     dow, and will clip any subwindows.

default bounding region

     The rectangular area, as described by the core protocol
     window size, that covers the interior of the window and
     its border.

default clip region

     The rectangular area, as described by the core protocol
     window size, that covers the interior of the window and
     excludes the border.

client bounding region

     The region associated with a window that is directly
     modified via this extension when specified by
     ShapeBounding.  This region is used in conjunction with
     the default bounding region to produce the effective
     bounding region.

client clip region

     The region associated with a window that is directly
     modified via this extension when specified by
     ShapeClip.  This region is used in conjunction with the
     default clip region and the client bounding region to
     produce the effective clip region.

effective bounding region

     The actual shape of the window on the screen, including
     border and interior (but excluding the effects of over-
     lapping windows).	When a window has a client bounding
     region, the effective bounding region is the intersec-
     tion of the default bounding region and the client
     bounding region.  Otherwise, the effective bounding
     region is the same as the default bounding region.












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     X11 Nonrectangular Window Shape Extension Protocol


effective clip region

     The actual shape of the interior of the window on the
     screen (excluding the effects of overlapping windows).
     When a window has a client clip region or a client
     bounding region, the effective clip region is the
     intersection of the default clip region, the client
     clip region (if any) and the client bounding region (if
     any).  Otherwise, the effective clip region is the same
     as the default clip region.















































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