Clipboard management

[Matthias Clasen]

Here is a new version of the clipboard management proposal.
I've incorporated the TARGET_SIZES proposal did some rewording.
If nobody has major issues with this, I'll put this up in place of the
current _NET_MAX_SELECTION_SIZE proposal on freedesktop.org 
in a few days.

Matthias 


-------------- next part --------------
Clipboard Manager Specification
===============================

Responsibilities of clipboard managers
--------------------------------------

Clipboard managers will acquire ownership of a selection named
CLIPBOARD_MANAGER, as described in section 1.2.6 of the ICCCM. Clipboard
managers should comply with the conventions for "Manager Selections" described
in section 2.8 of the ICCCM. The intent is for clients to be able to request a
variety of information or services by issuing conversion requests on this
selection. 

Clipboard managers should support conversion of the SAVE_TARGETS target on their
manager selection. This is a side-effect target, as described in ICCCM section
2.6.3.

When a clipboard manager receives a request to convert the manager selection to
the target SAVE_TARGETS, the named property specifies a list of targets to
convert the CLIPBOARD selection to. If the named property exists, it must be of
type ATOM and contain the list of targets. If the named property does not exist,
the list of targets should be obtained by converting the CLIPBOARD to the
TARGETS target, excluding side effect targets like DELETE, INSERT_PROPERTY and 
INSERT_SELECTION and possibly reducing the list of targets further.

If the clipboard owner supports the TARGET_SIZES target, the clipboard manager 
may use that to determine how to handle the SAVE_TARGETS request, possibly 
refusing to save large amounts of data, or asking the user before doing so.

When handling SAVE_TARGETS, the clipboard manager should convert the CLIPBOARD
selection to the selected targets. Then it should take over ownership of the 
CLIPBOARD selection and offer the saved conversion results under the same targets 
they were requested with.


Responsibilities of clipboard owners
------------------------------------

In order to support clipboard managers who want to avoid storing large amounts
of data, clipboard owners should support a target named TARGET_SIZES. When asked
to convert the clipboard to TARGET_SIZES, the clipboard owner must set the named 
property to format 32, type ATOM, and fill it with a list of pairs of target atoms 
and integers. There should be exactly one list entry for each supported target, 
and the integer should be
a) -1 for side effect targets, or
b) an estimate of the size in bytes of the result of converting the current
   CLIPBOARD contents to the target, or
c) 0 if it is too hard or impossible to determine the size, e.g. for MULTIPLE.

If an application needs to exit while owning the CLIPBOARD selection, they
should request the clipboard manager to take over the ownership of the clipboard,
using the SAVE_TARGETS mechanism. If there is no clipboard manager, or if the
SAVE_TARGETS conversion fails, the application should simply exit.

I order to support peers who use the XFIXES extension to watch clipboard ownership
changes, clipboard owners should reacquire the clipboard whenever the content
or metadata (e.g the list of supported targets) changes.