495 lines
14 KiB
Plaintext
495 lines
14 KiB
Plaintext
The XFIXES Extension
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Version 2.0
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Document Revision 1
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2003-11-20
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Keith Packard
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keithp@keithp.com
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1. Introduction
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X applications have often needed to work around various shortcomings in the
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core X window system. This extension is designed to provide the minimal
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server-side support necessary to eliminate problems caused by these
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workarounds.
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2. Acknowledgements
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This extension is a direct result of requests made by application
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developers, in particular,
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+ Owen Taylor for describing the issues raised with the XEMBED
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mechanisms and SaveSet processing and his initial extension
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to handle this issue.
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+ Bill Haneman for the design for cursor image tracking.
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+ Havoc Pennington
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+ Fredrik Höglund for cursor names
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3. Basic Premise
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Requests in this extension may seem to wander all over the map of X server
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capabilities, but they are tied by a simple rule -- resolving issues raised
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by application interaction with core protocol mechanisms that cannot be
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adequately worked around on the client side of the wire.
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4. Extension initialization
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The client must negotiate the version of the extension before executing
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extension requests. Behavior of the server is undefined otherwise.
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QueryVersion
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client-major-version: CARD32
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client-minor-version: CARD32
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->
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major-version: CARD32
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minor-version: CARD32
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The client sends the highest supported version to the server and
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the server sends the highest version it supports, but no higher than
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the requested version. Major versions changes can introduce
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incompatibilities in existing functionality, minor version
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changes introduce only backward compatible changes. It is
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the clients responsibility to ensure that the server supports
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a version which is compatible with its expectations.
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************* XFIXES VERSION 1 OR BETTER ***********
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5. Save Set processing changes
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Embedding one application within another provides a way of unifying
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disparate documents and views within a single framework. From the X
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protocol perspective, this appears similar to nested window managers; the
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embedding application "manages" the embedded windows much as a window
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manager does for top-level windows. To protect the embedded application
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from embedding application failure, it is reasonable to use the core SaveSet
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mechanism so that embedding application failure causes embedded windows to
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be preserved instead of destroyed.
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The core save set mechanism defines the target for each save set member
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window as the nearest enclosing window not owned by the terminating client.
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For embedding applications, this nearest window is usually the window
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manager frame. The problem here is that the window manager will not
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generally expect to receive and correctly manage new windows appearing within
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that window by the save set mechanism, and will instead destroy the frame
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window in response to the client window destruction. This causes the
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embedded window to be destroyed.
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An easy fix for this problem is to change the target of the save set member
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to a window which won't be affected by the underlying window destruction.
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XFIXES chooses the root window as the target.
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Having embedded windows suddenly appear at the top level can confuse users,
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so XFIXES also permits these windows to remain unmapped instead of being
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remapped.
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5.1 Requests
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ChangeSaveSet
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window: Window
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mode: { Insert, Delete }
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target: { Nearest, Root }
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map: { Map, Unmap }
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ChangeSaveSet is an extension of the core protocol ChangeSaveSet
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request. As in that request, mode specifies whether the indicated
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window is inserted or deleted from the save-set. Target specifies
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whether the window is reparented to the nearest non-client window as
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in the core protocol, or reparented to the root window. Map
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specifies whether the window is mapped as in the core protocol or
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unmapped.
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6. Selection Tracking
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Applications wishing to monitor the contents of current selections must
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poll for selection changes. XFIXES improves this by providing an event
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delivered whenever the selection ownership changes.
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6.1 Types
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SELECTIONEVENT { SetSelectionOwner,
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SelectionWindowDestroy,
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SelectionClientClose }
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6.1 Events
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SelectionNotify
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subtype: SELECTIONEVENT
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window: Window
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owner: Window
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selection: Atom
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timestamp: Timestamp
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selection-timestamp: Timestamp
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6.2 Requests
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SelectSelectionInput
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window: Window
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selection: Atom
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event-mask: SETofSELECTIONEVENT
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Selects for events to be delivered to window when various causes of
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ownership of selection occur. Subtype indicates the cause of the
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selection ownership change. Owner is set to the current selection
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owner, or None. Timestamp indicates the time the event was
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generated while selection-timestamp indicates the timestamp used to
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own the selection.
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7. Cursor Image Monitoring
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Mirroring the screen contents is easily done with the core protocol or VNC
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addons, except for the current cursor image. There is no way using the core
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protocol to discover which cursor image is currently displayed. The
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cursor image often contains significant semantic content about the user
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interface. XFIXES provides a simple mechanism to discover when the cursor
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image changes and to fetch the current cursor image.
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As the current cursor may or may not have any XID associated with it, there
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is no stable name available. Instead, XFIXES returns only the image of the
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current cursor and provides a way to identify cursor images to avoid
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refetching the image each time it changes to a previously seen cursor.
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7.1 Types
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CURSOREVENT { DisplayCursor }
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7.2 Events
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CursorNotify
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subtype: CURSOREVENT
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window: Window
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cursor-serial: CARD32
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timestamp: Timestamp
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name: Atom (Version 2 only)
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7.3 Requests
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SelectCursorInput
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window: Window
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event-mask: SETofCURSOREVENT
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This request directs cursor change events to the named window.
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Events will be delivered irrespective of the screen on which they
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occur. Subtype indicates the cause of the cursor image change
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(there is only one subtype at present). Cursor-serial is a number
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assigned to the cursor image which identifies the image. Cursors
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with different serial numbers may have different images. Timestamp
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is the time of the cursor change.
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GetCursorImage
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->
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x: INT16
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y: INT16
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width: CARD16
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height: CARD16
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x-hot: CARD16
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y-hot: CARD16
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cursor-serial: CARD32
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cursor-image: LISTofCARD32
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GetCursorImage returns the image of the current cursor. X and y are
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the current cursor position. Width and height are the size of the
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cursor image. X-hot and y-hot mark the hotspot within the cursor
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image. Cursor-serial provides the number assigned to this cursor
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image, this same serial number will be reported in a CursorNotify
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event if this cursor image is redisplayed in the future.
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The cursor image itself is returned as a single image at 32 bits per
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pixel with 8 bits of alpha in the most significant 8 bits of the
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pixel followed by 8 bits each of red, green and finally 8 bits of
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blue in the least significant 8 bits. The color components are
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pre-multiplied with the alpha component.
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************* XFIXES VERSION 2 OR BETTER ***********
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8. Region Objects
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The core protocol doesn't expose regions as a primitive object and this
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makes many operations more complicated than they really need to be. Adding
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region objects simplifies expose handling, the Shape extension and other
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operations. These operations are also designed to support a separate
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extension, the X Damage Extension.
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8.1 Types
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Region: XID
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WINDOW_REGION_KIND: { Bounding, Clip }
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8.2 Errors
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Region The specified region is invalid
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8.3 Requests
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CreateRegion
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region: REGION
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rects: LISTofRECTANGLE
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Creates a region initialized to the specified list of rectangles.
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The rectangles may be specified in any order, their union becomes
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the region. The core protocol allows applications to specify an
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order for the rectangles, but it turns out to be just as hard to
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verify the rectangles are actually in that order as it is to simply
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ignore the ordering information and union them together. Hence,
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this request dispenses with the ordering information.
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Errors: IDChoice
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CreateRegionFromBitmap
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region: REGION
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bitmap: PIXMAP
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Creates a region initialized to the set of 'one' pixels in bitmap
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(which must be depth 1, else Match error).
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Errors: Pixmap, IDChoice, Match
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CreateRegionFromWindow
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window: Window
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kind: WINDOW_REGION_KIND
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region: Region
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Creates a region initialized to the specified window region. See the
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Shape extension for the definition of Bounding and Clip regions.
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Errors: Window, IDChoice, Value
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CreateRegionFromGC
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gc: GContext
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region: Region
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Creates a region initialized from the clip list of the specified
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GContext.
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Errors: GContext, IDChoice
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CreateRegionFromPicture
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picture: Picture
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region: Region
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Creates a region initialized from the clip list of the specified
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Picture.
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Errors: Picture, IDChoice
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DestroyRegion
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region: Region
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Destroys the specified region.
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Errors: Region
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SetRegion
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region: Region
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rects: LISTofRECTANGLE
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This replaces the current contents of region with the region formed
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by the union of rects.
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CopyRegion
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source: Region
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destination: Region
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This replaces the contents of destination with the contents of
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source.
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UnionRegion
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IntersectRegion
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SubtractRegion
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source1: Region
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source2: Region
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destination: Region
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Combines source1 and source2, placing the result in destination.
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Destination may be the same as either source1 or source2.
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Errors: Region, Value
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InvertRegion
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source: Region
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bounds: RECTANGLE
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destination: Region
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The source region is subtracted from the region specified by
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bounds. The result is placed in destination, replacing its contents.
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Errors: Region
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TranslateRegion
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region: Region
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dx, dy: INT16
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The region is translated by dx, dy in place.
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Errors: Region
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RegionExtents
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source: Region
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destination: Region
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The extents of the source region are placed in the destination
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FetchRegion
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region: Region
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->
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extents: RECTANGLE
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rectangles: LISTofRECTANGLE
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The region is returned as a list of rectangles in YX-banded order.
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Errors: Region
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SetGCClipRegion
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gc: GCONTEXT
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clip-x-origin, clip-y-origin: INT16
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region: Region or None
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This request changes clip-mask in gc to the specified region and
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sets the clp origin. Output will be clippped to remain contained
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within the region. The clip origin is interpreted relative to the
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origin of whatever destination drawable is specified in a graphics
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request. The region is interpreted relative to the clip origin.
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Future changes to region have no effect on the gc clip-mask.
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Errors: GContext, Region
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SetWindowShapeRegion
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dest: Window
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destKind: SHAPE_KIND
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xOff, yOff: INT16
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region: Region or None
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This request sets the specified (by destKind) Shape extension region
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of the window to region, offset by xOff and yOff. Future changes to
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region have no effect on the window shape.
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Errors: Window, Value, Region
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SetPictureClipRegion
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picture: Picture
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clip-x-origin, clip-y-origin: INT16
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region: Region or None
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This request changes clip-mask in picture to the specified region
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and sets the clip origin. Input and output will be clipped to
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remain contained within the region. The clip origin is interpreted
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relative to the origin of the drawable associated with picture. The
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region is interpreted relative to the clip origin. Future changes
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to region have no effect on the picture clip-mask.
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Errors: Picture, Region
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9. Cursor Names
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Attaching names to cursors permits some abstract semantic content to be
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associated with specific cursor images. Reflecting those names back to
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applications allows that semantic content to be related to the user through
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non-visual means.
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9.1 Events
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CursorNotify
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subtype: CURSOREVENT
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window: Window
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cursor-serial: CARD32
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timestamp: Timestamp
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name: Atom or None
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In Version 2 of the XFIXES protocol, this event adds the atom
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of any name associated with the current cursor (else None).
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9.2 Requests
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SetCursorName
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cursor: CURSOR
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name: LISTofCARD8
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This request interns name as an atom and sets that atom as the name
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of cursor.
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Errors: Cursor
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GetCursorName
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cursor: CURSOR
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->
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atom: ATOM or None
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name: LISTofCARD8
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This request returns the name and atom of cursor. If no name is
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set, atom is None and name is empty.
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Errors: Cursor
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GetCursorImageAndName
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->
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x: INT16
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y: INT16
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width: CARD16
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height: CARD16
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x-hot: CARD16
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y-hot: CARD16
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cursor-serial: CARD32
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cursor-atom: ATOM
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cursor-name: LISTofCARD8
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cursor-image: LISTofCARD32
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This is similar to GetCursorImage except for including both
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the atom and name of the current cursor.
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ChangeCursor
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source, destination: CURSOR
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This request replaces all references to the destination with a
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reference to source. Any existing uses of the destination cursor
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object will now show the source cursor image.
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ChangeCursorByName
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src: CURSOR
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name: LISTofCARD8
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This request replaces the contents of all cursors with the specified
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name with the src cursor.
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99. Future compatibility
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This extension is not expected to remain fixed. Future changes will
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strive to remain compatible if at all possible. The X server will always
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support version 1 of the extension protocol if requested by a client.
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Additions to the protocol will always by marked by minor version number
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changes so that applications will be able to detect what requests are
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supported.
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