xref: /xsrc/external/mit/libXext/dist/specs/shapelib.xml

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<book id="shapelib">

<bookinfo>
   <title>X Nonrectangular Window Shape Extension Library</title>
   <subtitle>X Consortium Standard</subtitle>
   <releaseinfo>X Version 11, Release &fullrelvers;</releaseinfo>
   <releaseinfo>Version 1.0</releaseinfo>
   <authorgroup>
      <author>
         <firstname>Keith</firstname><surname>Packard</surname>
         <affiliation><orgname>MIT X Consortium</orgname></affiliation>
      </author>
   </authorgroup>
   <copyright><year>1989</year><holder>X Consortium</holder></copyright>

<legalnotice>

<para>
Permission is hereby granted, free of charge, to any person obtaining a copy
of this software and associated documentation files
(the &ldquo;Software&rdquo;), to deal in the Software without restriction,
including without limitation the rights to use, copy, modify, merge,
publish, distribute, sublicense, and/or sell copies of the Software, and
to permit persons to whom the Software is furnished to do so, subject to
the following conditions:
</para>

<para>
The above copyright notice and this permission notice shall be included in
all copies or substantial portions of the Software.
</para>

<para>
THE SOFTWARE IS PROVIDED &ldquo;AS IS&rdquo;, WITHOUT WARRANTY OF ANY
KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES
OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.
IN NO EVENT SHALL THE X CONSORTIUM BE LIABLE FOR ANY CLAIM, DAMAGES OR
OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE,
ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR
OTHER DEALINGS IN THE SOFTWARE.
</para>

<para>
Except as contained in this notice, the name of the X Consortium shall not be
used in advertising or otherwise to promote the sale, use or other dealings
in this Software without prior written authorization from the X Consortium.
</para>
<para>X Window System is a trademark of The OpenGroup.</para>
</legalnotice>
</bookinfo>

<chapter id='overview'>
<title>Overview</title>

<para>This extension provides arbitrary window and border shapes within
the X11 protocol.
</para>

<para>
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 windows would like to display a
&ldquo;drop shadow&rdquo; to give the illusion of 3 dimensions.  As
another example, some user interface style guides call for buttons with
rounded corners; the full simulation of a nonrectangular shape,
particularly 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.
</para>

<para>
This extension provides mechanisms for changing the visible shape of a
window to an arbitrary, possibly disjoint, nonrectangular form.  The intent
of the extension is to supplement the existing semantics, not replace them.
In particular, 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 convention would be
that client programs expand their shape to fill the area offered by the
window manager.
</para>
</chapter>

<chapter id='description'>
<title>Description</title>

<para>
Each window (even with no shapes specified) is defined by two regions:  the
<olink targetdoc='shapelib' targetptr='bounding_region'>bounding region</olink>
and the
<olink targetdoc='shapelib' targetptr='clip_region'>clip region</olink>.
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
subwindows and graphics.  The area between the bounding region and the
clip region is defined to be the border of the window.
</para>

<para>
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 dimensions (not including the border).  In this document,
these areas are referred to as the
<olink targetdoc='shapelib' targetptr='default_bounding_region'>
default bounding region</olink> and the
<olink targetdoc='shapelib' targetptr='default_clip_region'>
default clip region</olink>.  For a window with
inside size of <emphasis remap='I'>width</emphasis> by
<emphasis remap='I'>height</emphasis> and border width
<emphasis remap='I'>bwidth</emphasis>, the default bounding and clip
regions are the rectangles (relative to the window origin):
</para>

<literallayout remap='Ds'>
bounding.x = -<emphasis remap='I'>bwidth</emphasis>
bounding.y = -<emphasis remap='I'>bwidth</emphasis>
bounding.width = <emphasis remap='I'>width</emphasis> + 2 * <emphasis remap='I'>bwidth</emphasis>
bounding.height = <emphasis remap='I'>height</emphasis> + 2 * <emphasis remap='I'>bwidth</emphasis>

clip.x = 0
clip.y = 0
clip.width = <emphasis remap='I'>width</emphasis>
clip.height = <emphasis remap='I'>height</emphasis>
</literallayout>

<para>
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
<olink targetdoc='shapelib' targetptr='client_bounding_region'>
client bounding region</olink> and the
<olink targetdoc='shapelib' targetptr='client_clip_region'>
client clip region</olink>.  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.
</para>

<para>
When using an existing window shape as an operand in specifying a new shape,
the client region is used, unless none has been set, in which case the
default region is used instead.
</para>

<para>
The <olink targetdoc='shapelib' targetptr='effective_bounding_region'>
effective bounding region</olink> 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.
</para>

<para>
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.
</para>

<para>
The <olink targetdoc='shapelib' targetptr='effective_clip_region'>
effective clip region</olink> 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 default clip region
and the client bounding region will not be included in the effective clip
region on the screen.
</para>

<para>
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
window 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.
</para>

<para>
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.
</para>

<para>
All output to the window and visible regions of any subwindows 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.
</para>

<para>
Areas that are inside the default bounding region but outside the effective
bounding region are not part of the window; these areas of the screen will
be occupied by other windows.  Input events that occur within the default
bounding region but outside the effective bounding region will be delivered as
if the window was not occluding the event position.  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.
</para>

<para>An
<olink targetdoc='libX11' targetptr='glossary:InputOnly_window'>
InputOnly</olink>
window can have its bounding region set, but it is a
<olink targetdoc='libX11' targetptr='BadMatch'>Match</olink>
error to attempt to set a clip region on an
<olink targetdoc='libX11' targetptr='glossary:InputOnly_window'>InputOnly</olink>
window or to specify its clip region as a source to a request
in this extension.
</para>

<para>
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 dependent.
</para>
</chapter>

<chapter id='c_language_binding'>
<title>C Language Binding</title>

<para>
The C functions provide direct access to the protocol and add no additional
semantics.
</para>

<para>The include file for this extension is
&lt;<symbol role='Pn'>X11/extensions/shape.h</symbol>&gt;.
The defined shape kinds are
<function>ShapeBounding</function>
and
<function>ShapeClip</function>
The defined region operations are
<function>ShapeSet</function>
<function>ShapeUnion</function>
<function>ShapeIntersect</function>
<function>ShapeSubtract</function>
and
<function>ShapeInvert</function>.</para>

<funcsynopsis id='xshapequeryextension'>
<funcprototype>
<funcdef>Bool<function> XShapeQueryExtension</function></funcdef>
<paramdef>Display <parameter>*display</parameter></paramdef>
<paramdef>int <parameter>*event_base</parameter></paramdef>
<paramdef>int <parameter>*error_base</parameter></paramdef>
</funcprototype>
</funcsynopsis>

<para>
<function>XShapeQueryExtension</function>
returns
<function>True</function>
if the specified display supports the SHAPE extension else
<function>False</function>
If the extension is supported, *event_base is set to the event number for
<function>ShapeNotify</function>
events and *error_base would be set to the error number for the first error for
this extension.  Because no errors are defined for this version of
the extension, the value returned here is not defined (nor useful).
</para>

<funcsynopsis id='xshapequeryversion'>
<funcprototype>
<funcdef>Status<function> XShapeQueryVersion</function></funcdef>
<paramdef>Display<parameter> *display</parameter></paramdef>
<paramdef>int<parameter> *major_version</parameter></paramdef>
<paramdef>int<parameter> *minor_version</parameter></paramdef>
</funcprototype>
</funcsynopsis>

<para>
If the extension is supported,
<function>XShapeQueryVersion</function>
sets the major and minor version numbers of the
extension supported by the display and returns a nonzero value.
Otherwise, the arguments are not set and zero is returned.
</para>

<funcsynopsis id='xshapecombineregion'>
<funcprototype>
<funcdef><function>XShapeCombineRegion</function></funcdef>
<paramdef>Display<parameter> *display</parameter></paramdef>
<paramdef>Window<parameter> dest</parameter></paramdef>
<paramdef>int<parameter> dest_kind</parameter></paramdef>
<paramdef>int<parameter> x_off</parameter></paramdef>
<paramdef>int<parameter> y_off</parameter></paramdef>
<paramdef>int<parameter> region</parameter></paramdef>
<paramdef>int<parameter> op</parameter></paramdef>
<paramdef>REGION<parameter> *region</parameter></paramdef>
</funcprototype>
</funcsynopsis>

<para>
<function>XShapeCombineRegion</function>
converts the specified region into a list of rectangles and calls
<function>XShapeCombineRectangles</function>
</para>

<funcsynopsis id='xshapecombinerectangles'>
<funcprototype>
<funcdef><function>XShapeCombineRectangles</function></funcdef>
<paramdef>Display<parameter> *display</parameter></paramdef>
<paramdef>Window<parameter> dest</parameter></paramdef>
<paramdef>int<parameter> dest_kind</parameter></paramdef>
<paramdef>int<parameter> x_off</parameter></paramdef>
<paramdef>int<parameter> y_off</parameter></paramdef>
<paramdef>XRectangle<parameter> *rectangles</parameter></paramdef>
<paramdef>int<parameter> n_rects</parameter></paramdef>
<paramdef>int<parameter> op</parameter></paramdef>
<paramdef>int<parameter> ordering</parameter></paramdef>
</funcprototype>
</funcsynopsis>

<para>
If the extension is supported,
<function>XShapeCombineRectangles</function>
performs a
<function>ShapeRectangles</function>
operation; otherwise, the request is ignored.
</para>

<funcsynopsis id='xshapecombinemask'>
<funcprototype>
<funcdef><function>XShapeCombineMask</function></funcdef>
<paramdef>Display<parameter> *display</parameter></paramdef>
<paramdef>int<parameter> dest</parameter></paramdef>
<paramdef>int<parameter> dest_kind</parameter></paramdef>
<paramdef>int<parameter> x_off</parameter></paramdef>
<paramdef>int<parameter> y_off</parameter></paramdef>
<paramdef>Pixmap<parameter> src</parameter></paramdef>
<paramdef>int<parameter> op</parameter></paramdef>
</funcprototype>
</funcsynopsis>

<para>
If the extension is supported,
<function>XShapeCombineMask</function>
performs a
<function>ShapeMask</function>
operation; otherwise, the request is ignored.
</para>

<funcsynopsis id='xshapecombineshape'>
<funcprototype>
<funcdef><function>XShapeCombineShape</function></funcdef>
<paramdef>Display<parameter> *display</parameter></paramdef>
<paramdef>Window<parameter> dest</parameter></paramdef>
<paramdef>int<parameter> dest_kind</parameter></paramdef>
<paramdef>int<parameter> x_off</parameter></paramdef>
<paramdef>int<parameter> y_off</parameter></paramdef>
<paramdef>Window<parameter> src</parameter></paramdef>
<paramdef>int<parameter> src_kind</parameter></paramdef>
<paramdef>int<parameter> op</parameter></paramdef>
</funcprototype>
</funcsynopsis>

<para>
If the extension is supported,
<function>XShapeCombineShape</function>
performs a
<function>ShapeCombine</function>
operation; otherwise, the request is ignored.
</para>

<funcsynopsis id='xshapeoffsetshape'>
<funcprototype>
<funcdef><function>XShapeOffsetShape</function></funcdef>
<paramdef><parameter>display</parameter></paramdef>
<paramdef><parameter>dest</parameter></paramdef>
<paramdef><parameter>dest_kind</parameter></paramdef>
<paramdef><parameter>x_off</parameter></paramdef>
<paramdef><parameter>y_off</parameter></paramdef>
</funcprototype>
</funcsynopsis>

<para>
If the extension is supported,
<function>XShapeOffsetShape</function>
performs a
<function>ShapeOffset</function>
operation; otherwise, the request is ignored.
</para>

<funcsynopsis id='xshapequeryextents'>
<funcprototype>
<funcdef>Status <function>XShapeQueryExtents</function></funcdef>
<paramdef>Display<parameter> *display</parameter></paramdef>
<paramdef>Window<parameter> window</parameter></paramdef>
<paramdef>Bool<parameter> *bounding_shaped</parameter></paramdef>
<paramdef>int<parameter> *x_bounding</parameter></paramdef>
<paramdef>int<parameter> *y_bounding</parameter></paramdef>
<paramdef>unsigned int<parameter> *w_bounding</parameter></paramdef>
<paramdef>unsigned int<parameter> *h_bounding</parameter></paramdef>
<paramdef>Bool<parameter> *clip_shaped</parameter></paramdef>
<paramdef>int<parameter> *x_clip</parameter></paramdef>
<paramdef>int<parameter> *y_clip</parameter></paramdef>
<paramdef>unsigned int<parameter> *w_clip</parameter></paramdef>
<paramdef>unsigned int<parameter> *h_clip</parameter></paramdef>
</funcprototype>
</funcsynopsis>

<para>
If the extension is supported,
<function>XShapeQueryExtents</function>
sets x_bounding, y_bounding, w_bounding, h_bounding to the extents of the
bounding shape and sets x_clip, y_clip, w_clip, h_clip to the extents of
the clip shape.  For unspecified client regions, the extents of the
corresponding default region are used.
</para>

<para>
If the extension is supported, a nonzero value is returned; otherwise,
zero is returned.
</para>

<funcsynopsis id='xshapeselectinput'>
<funcprototype>
<funcdef><function>XShapeSelectInput</function></funcdef>
<paramdef>Display<parameter> *display</parameter></paramdef>
<paramdef>Window<parameter> window</parameter></paramdef>
<paramdef>unsigned long<parameter> mask</parameter></paramdef>
</funcprototype>
</funcsynopsis>

<para>
To make this extension more compatible with other interfaces, although
only one event type can be selected via the extension,
<function>XShapeSelectInput</function>
provides a general mechanism similar to the standard Xlib binding for
window events.  A mask value has been defined,
<function>ShapeNotifyMask</function>
that is the only valid bit in mask that may be specified.
The structure for this event is defined as follows:
</para>

<literallayout remap='Ds'>
typedef struct {
    int type;     /* of event */
    unsigned long serial;     /* # of last request processed by server */
    Bool send_event;     /* true if this came from a SendEvent request */
    Display *display;     /* Display the event was read from */
    Window window;     /* window of event */
    int kind;     /* ShapeBounding or ShapeClip */
    int x, y;     /* extents of new region */
    unsigned width, height;
    Time time;     /* server timestamp when region changed */
    Bool shaped;     /* true if the region exists */
} XShapeEvent;
</literallayout>

<funcsynopsis id='xshapeinputselected'>
<funcprototype>
<funcdef>unsigned long <function>XShapeInputSelected</function></funcdef>
<paramdef>Display<parameter> *display</parameter></paramdef>
<paramdef>Window<parameter> window</parameter></paramdef>
</funcprototype>
</funcsynopsis>

<para>
<function>XShapeInputSelected</function>
returns the current input mask for extension events on the specified
window; the value returned if
<function>ShapeNotify</function>
is selected for is
<function>ShapeNotifyMask</function>
otherwise, it returns zero.
If the extension is not supported, it returns zero.
</para>

<funcsynopsis id='xshapegetrectangles'>
<funcprototype>
<funcdef>XRectangle<function> *XShapeGetRectangles</function></funcdef>
<paramdef>Display<parameter> *display</parameter></paramdef>
<paramdef>Window<parameter> window</parameter></paramdef>
<paramdef>int<parameter> kind</parameter></paramdef>
<paramdef>int<parameter> *count</parameter></paramdef>
<paramdef>int<parameter> *ordering</parameter></paramdef>
</funcprototype>
</funcsynopsis>

<para>
If the extension is not supported,
<function>XShapeGetRectangles</function>
returns NULL.  Otherwise, it returns a list of rectangles that describe the
region specified by kind.
</para>
</chapter>

<glossary id='glossary'>

<glossentry id='bounding_region'>
  <glossterm>bounding region</glossterm>
  <glossdef><para>The area of the parent window that this window will occupy.
This area is divided into two parts:  the border and the interior.</para>
  </glossdef>
</glossentry>

<glossentry id='clip_region'>
  <glossterm>clip region</glossterm>
  <glossdef><para>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 window, and will clip any subwindows.</para></glossdef>
</glossentry>

<glossentry id='default_bounding_region'>
  <glossterm>default bounding region</glossterm>
  <glossdef><para>The rectangular area, as described by the core protocol
window size, that covers the interior of the window and its border.</para>
  </glossdef>
</glossentry>

<glossentry id='default_clip_region'>
  <glossterm>default clip region</glossterm>
  <glossdef><para>The rectangular area, as described by the core protocol
window size, that covers the interior of the window and excludes the border.
  </para></glossdef>
</glossentry>

<glossentry id='client_bounding_region'>
  <glossterm>client bounding region</glossterm>
  <glossdef><para>The region associated with a window that is directly
modified via this extension when specified by
<function>ShapeBounding</function>
This region is used in conjunction with the default bounding region
to produce the effective bounding region.</para></glossdef>
</glossentry>

<glossentry id='client_clip_region'>
  <glossterm>client clip region</glossterm>
  <glossdef><para>The region associated with a window that is directly
modified via this extension when specified by
<function>ShapeClip</function>
This region is used in conjunction with the default clip region
and the client bounding region to produce the effective clip region.</para>
  </glossdef>
</glossentry>

<glossentry id='effective_bounding_region'>
  <glossterm>effective bounding region</glossterm>
  <glossdef><para>The actual shape of the window on the screen, including
border and interior (but excluding the effects of overlapping windows).
When a window has a client bounding region, the effective bounding region
is the intersection of the default bounding region and the client bounding
region.  Otherwise, the effective bounding region is the same as the
default bounding region.</para>
  </glossdef>
</glossentry>

<glossentry id='effective_clip_region'>
  <glossterm>effective clip region</glossterm>
  <glossdef><para>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.</para>
  </glossdef>
</glossentry>
</glossary>
</book>