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diff --git a/X11/extensions/geproto.txt b/X11/extensions/geproto.txt new file mode 100644 index 000000000..654cd0f70 --- /dev/null +++ b/X11/extensions/geproto.txt @@ -0,0 +1,83 @@ + X Generic Event Extension + Peter Hutterer + peter.hutterer@who-t.net + + +1. Introduction +2. Extension Initialization +3. Extension Events +4. Notes + +_____________________________________________________________________________ +1. Introduction + +X was designed to provide 64 event opcodes for all extensions. These events +are limited to 32 bytes. + +The Generic Event Extension provides a template event for extensions to re-use +a single event opcode. GE only provide headers and the most basic +functionality, leaving the extensions to interpret the events in their +specific context. + +GenericEvents may be longer than 32 bytes. If so, the number of 4 byte units +following the initial 32 bytes must be specified in the length field of the +event. +_____________________________________________________________________________ +2. Extension Initialization + +The name of this extension is "Generic Event Extension" + +┌─── + GEQueryVersion + client-major-version: CARD16 + client-minor-version: CARD16 + ▶ + major-version: CARD16 + minor-version: CARD16 +└─── + + The client sends the highest supported version to the server + and the server sends the highest version it supports, but no + higher than the requested version. Major versions changes can + introduce incompatibilities in existing functionality, minor + version changes introduce only backward compatible changes. + It is the clients responsibility to ensure that the server + supports a version which is compatible with its expectations. + + + As of version 1.0, no other requests are provided by this extension. +_____________________________________________________________________________ +3. Extension Events + +GE defines a single event, to be used by all extensions. The event's structure +is similar to a reply. + +┌─── + GenericEvent + type: BYTE; always GenericEvent + extension: CARD8; extension offset + sequenceNumber: CARD16 low 16 bits of request seq. number + length: CARD32 length + evtype: CARD16 event type +└─── + + The field 'extension' is to be set to the major opcode of the + extension. The 'evtype' field is the actual opcode of the event. + The length field specifies the number of 4-byte blocks after the + initial 32 bytes. If length is 0, the event is 32 bytes long. +_____________________________________________________________________________ +4. Notes + +Although the wire event is of arbitrary length, the actual size of an XEvent +is restricted to sizeof(XEvent) [96 bytes, see Xlib.h]. If an extension +converts a wire event to an XEvent > 96 bytes, it will overwrite the space +allocated for the event. See struct _XSQEvent in Xlibint.h for details. + +Extensions need to malloc additional data and fill the XEvent structure with +pointers to the malloc'd data. The client then needs to free the data, only +the XEvent structure will be released by Xlib. + +The server must not send GenericEvents longer than 32 bytes until it has +verified that the client is able to interpret these events. If a long event is +sent to a client unable to process GenericEvents, future interpretation of +replies and events by this client will fail. |