RFC: frame size hints

[Thomas Fitzsimmons <fitzsim redhat com>]

Hello,

This is a proposal for a new application window property,
_NET_FRAME_EXTENTS, and a new root window message,
_NET_REQUEST_FRAME_EXTENTS.  These additions allow a client to know the
extents of its window frame.

Havoc described the need for such extensions in this message:

http://mail.gnome.org/archives/wm-spec-list/2002-November/msg00051.html

and proposed an implementation here:

http://mail.gnome.org/archives/wm-spec-list/2003-January/msg00048.html

I've implemented this extension for Metacity and have used it to
implement GNU Classpath's java.awt.Window API.

Comments?

Tom

    <sect2><title>_NET_REQUEST_FRAME_EXTENTS</title>
	<programlisting><![CDATA[
_NET_REQUEST_FRAME_EXTENTS
  window = window for which to set _NET_FRAME_EXTENTS
  message_type = _NET_REQUEST_FRAME_EXTENTS
]]></programlisting>
	<para>
A client that wishes to know the extents of its window's frame should
send this message to the root window.  The window manager should
respond by setting the window's _NET_FRAME_EXTENTS property.
	</para>
	</para>
If the window manager receives a _NET_REQUEST_FRAME_EXTENTS message
before the window is mapped, it should estimate the frame extents that
the window would be given upon mapping, then set _NET_FRAME_EXTENTS
accordingly.
	</para>
	<para>
Rationale: A client cannot calculate the dimensions of its window's
frame before the window is mapped, but some toolkits need this
information.  Asking the window manager for an estimate is a workable
solution.  Extents estimates may depend on the current theme, font
sizes or other window properties.  The client can track changes to the
frame's dimensions by listening for _NET_FRAME_EXTENTS PropertyNotify
events.
	</para>
	</sect2>

	<sect2><title>_NET_FRAME_EXTENTS</title>
	<programlisting><![CDATA[
_NET_FRAME_EXTENTS, left, right, top, bottom, CARDINAL[4]/32
]]></programlisting>
	<para>
The window manager should set _NET_FRAME_EXTENTS to the extents of the
window's frame.  A window's frame extents are defined as follows:
	</para>
	<para>
left = x coordinate of window's left edge, relative to its frame's left
edge
right = frame_width - window_width - left
top = y coordinate of window's top edge, relative to its frame's top
edge
bottom = frame_height - window_height - top
	</para>
	</sect2>