xdg-shell: Add edge constraints

An edge constraint is an complementery state to the tiled state, meaning
that it's not only tiled, but constrained in a way that it can't resize
in that direction.

This typically means that the constrained edge is tiled against a
monitor edge. An example configuration is two windows tiled next to each
other on a single monitor. Together they cover the whole work area.

The left window would have the following tiled and edge constraint
state:

  [ tiled_top, tiled_right, tiled_bottom, tiled_left,
    constrained_top, constrained_bottom, constrained_left ]

while the right window would have the following:

  [ tiled_top, tiled_right, tiled_bottom, tiled_left,
    constrained_top, constrained_bottom, constrained_right ]

This aims to replace and deprecate the `gtk_surface1.configure_edges`
event and the `gtk_surface1.edge_constraint` enum.

Signed-off-by: Jonas Ådahl <jadahl@gmail.com>

stable/xdg-shell/xdg-shell.xml

@@ -29,7 +29,7 @@
     DEALINGS IN THE SOFTWARE.
   </copyright>
 
-  <interface name="xdg_wm_base" version="6">
+  <interface name="xdg_wm_base" version="7">
     <description summary="create desktop-style surfaces">
       The xdg_wm_base interface is exposed as a global object enabling clients
       to turn their wl_surfaces into windows in a desktop environment. It
@@ -122,7 +122,7 @@
     </event>
   </interface>
 
-  <interface name="xdg_positioner" version="6">
+  <interface name="xdg_positioner" version="7">
     <description summary="child surface positioner">
       The xdg_positioner provides a collection of rules for the placement of a
       child surface relative to a parent surface. Rules can be defined to ensure
@@ -407,7 +407,7 @@
     </request>
   </interface>
 
-  <interface name="xdg_surface" version="6">
+  <interface name="xdg_surface" version="7">
     <description summary="desktop user interface surface base interface">
       An interface that may be implemented by a wl_surface, for
       implementations that provide a desktop-style user interface.
@@ -617,7 +617,7 @@
 
   </interface>
 
-  <interface name="xdg_toplevel" version="6">
+  <interface name="xdg_toplevel" version="7">
     <description summary="toplevel surface">
       This interface defines an xdg_surface role which allows a surface to,
       among other things, set window-like properties such as maximize,
@@ -911,6 +911,38 @@
 	  outputs are switched off due to screen locking.
 	</description>
       </entry>
+      <entry name="constrained_left" value="10" since="7">
+	<description summary="the surface’s left edge is constrained">
+          The left edge of the window is currently constrained, meaning it
+          shouldn't attempt to resize from that edge. It can for example mean
+          it's tiled next to a monitor edge on the constrained side of the
+          window.
+	</description>
+      </entry>
+      <entry name="constrained_right" value="11" since="7">
+	<description summary="the surface’s right edge is constrained">
+          The right edge of the window is currently constrained, meaning it
+          shouldn't attempt to resize from that edge. It can for example mean
+          it's tiled next to a monitor edge on the constrained side of the
+          window.
+	</description>
+      </entry>
+      <entry name="constrained_top" value="12" since="7">
+	<description summary="the surface’s top edge is constrained">
+          The top edge of the window is currently constrained, meaning it
+          shouldn't attempt to resize from that edge. It can for example mean
+          it's tiled next to a monitor edge on the constrained side of the
+          window.
+	</description>
+      </entry>
+      <entry name="constrained_bottom" value="13" since="7">
+	<description summary="the surface’s bottom edge is tiled">
+          The bottom edge of the window is currently constrained, meaning it
+          shouldn't attempt to resize from that edge. It can for example mean
+          it's tiled next to a monitor edge on the constrained side of the
+          window.
+	</description>
+      </entry>
     </enum>
 
     <request name="set_max_size">
@@ -1207,7 +1239,7 @@
     </event>
   </interface>
 
-  <interface name="xdg_popup" version="6">
+  <interface name="xdg_popup" version="7">
     <description summary="short-lived, popup surfaces for menus">
       A popup surface is a short-lived, temporary surface. It can be used to
       implement for example menus, popovers, tooltips and other similar user