...and other net-wm-window-type atoms not already covered by wlroots.

Ref:

• xwayland: support querying more window types #1185
• Respect _NET_WM_WINDOW_TYPE_DESKTOP atom #1472
• xwayland: add sensible rules for NET_WM_WINDOW_TYPE_DESKTOP windows #1490

• labwc/docs/rc.xml.all

  Lines 519 to 525 in 59543e4

  	<windowRule title="pcmanfm-desktop*">
  	<skipTaskbar>yes</skipTaskbar>
  	<skipWindowSwitcher>yes</skipWindowSwitcher>
  	<fixedPosition>yes</fixedPosition>
  	<action name="MoveTo" x="0" y="0" />
  	<action name="ToggleAlwaysOnBottom"/>
  	</windowRule>

• https://github.com/swaywm/sway/blob/master/sway/criteria.c

Assuming we merge #1185, how would we actually implement support for something like _NET_WM_WINDOW_TYPE_DESKTOP.

Looking at the window-rules for pcmanfm-qt --desktop running in Wayland mode, we would need to consider

• <skipTaskbar>
• <skipWindowSwitcher>
• <fixedPosition>
• <action name="ToggleAlwaysOnBottom"/>

Action like ToggleAlwaysOnBottom could be processed in xwayland.c's handle_set_window_type() (introduced by #1185), but properties like fixedPosition would have to be checked for in the same positions where we currently do window_rules_get_property(), with the exception of some things which could be taken care of in xwayland_view_wants_focus().

Considering the amount of window-rule checks (see below), I think it would be ugly to add xwayland_surface_contains_window_type() the #if HAVE_XWAYLAND guards in all those places.

git grep window_rules_get_property:

src/desktop.c:          enum property skip = window_rules_get_property(view, "skipWindowSwitcher");
src/interactive.c:      if (window_rules_get_property(view, "fixedPosition") == LAB_PROP_TRUE
src/view-impl-common.c: enum property ret = window_rules_get_property(view, "skipTaskbar");
src/view.c:             if (window_rules_get_property(view, "skipWindowSwitcher") == LAB_PROP_TRUE) {
src/view.c:     if (window_rules_get_property(view, "fixedPosition") == LAB_PROP_TRUE
src/xdg.c:      switch (window_rules_get_property(view, "serverDecoration")) {
src/xdg.c:      if (window_rules_get_property(view, "ignoreFocusRequest") == LAB_PROP_TRUE) {
src/xwayland.c: switch (window_rules_get_property(view, "serverDecoration")) {
src/xwayland.c: if (window_rules_get_property(view, "ignoreFocusRequest") == LAB_PROP_TRUE) {

So, how do we do it?

@Consolatis and I brainstormed a bit on IRC and thought we might be able to extend the window-rule criteria to accept a wlr_surface rather than identifier, etc. and just add window rules for properties in the set_type handler? If that works, it would potentially be quite neat and self-contained within xwayland.c We'd probably have to deal with set_type()s happening after map().

Cc: @jlindgren90 @Consolatis @grisha128