xdg-shell: Add resize_x/y constraint adjustment to positioner

In order to get feedback of available space where a client can create
its popup, let it create requset that its popup rectangle being resized
would it not fit the within the work area. This adds two new constraint
adjustment values to the adjustment enum, and dimension parameters to
the xdg_popup.configure event.

The existing constraint adjustment actions take precedence, and resizing
will only be triggered if all other adjustments requested didn't manage
to make the popup rectangle fully visible.

Signed-off-by: Jonas Ådahl <jadahl@gmail.com>
Acked-by: Quentin Glidic <sardemff7+git@sardemff7.net>

unstable/xdg-shell/xdg-shell-unstable-v6.xml

@@ -234,6 +234,20 @@
     </request>
 
     <enum name="constraint_adjustment" bitfield="true">
+      <description summary="constraint adjustments">
+	The constraint adjustment value define ways the compositor will adjust
+	the position of the surface, if the unadjusted position would result
+	in the surface being partly constrained.
+
+	Whether a surface is considered 'constrained' is left to the compositor
+	to determine. For example, the surface may be partly outside the
+	compositor's defined 'work area', thus necessitating the child surface's
+	position be adjusted until it is entirely inside the work area.
+
+	The adjustments can be combined, according to a defined precedence: 1)
+	Flip, 2) Slide, 3) Resize.
+      </description>
+
       <entry name="none" value="0">
 	<description summary="don't move the child surface when constrained">
 	  Don't alter the surface position even if it is constrained on some
@@ -253,8 +267,6 @@
 	  x axis until either the edge in the direction of the gravity is
 	  unconstrained or the edge in the opposite direction of the gravity is
 	  constrained.
-
-	  If 'slide_x' is combined with 'flip_x', 'flip_x' takes precedence.
 	</description>
       </entry>
       <entry name="slide_y" value="2">
@@ -270,8 +282,6 @@
 	  y axis until either the edge in the direction of the gravity is
 	  unconstrained or the edge in the opposite direction of the gravity is
 	  constrained.
-
-	  If 'slide_y' is combined with 'flip_y', 'flip_y' takes precedence.
 	</description>
       </entry>
       <entry name="flip_x" value="4">
@@ -282,9 +292,8 @@
 	  'left', change the gravity to 'right' and the anchor to 'right'.
 
 	  If the adjusted position also ends up being constrained, the resulting
-	  position will be the one before the adjustment. If the resulting
-	  position is still constrained, and 'flip_x' is combined with
-	  'slide_x', the position is adjusted according to 'slide_x'.
+	  position of the flip_x adjustment will be the one before the
+	  adjustment.
 	</description>
       </entry>
       <entry name="flip_y" value="8">
@@ -295,9 +304,19 @@
 	  'bottom', change the gravity to 'top' and the anchor to 'top'.
 
 	  If the adjusted position also ends up being constrained, the resulting
-	  position will be the one before the adjustment. If the resulting
-	  position is still constrained, and 'flip_y' is combined with
-	  'slide_y', the position is adjusted according to 'slide_y'.
+	  position of the flip_y adjustment will be the one before the
+	  adjustment.
+	</description>
+      </entry>
+      <entry name="resize_x" value="16">
+	<description summary="horizontally resize the surface">
+	  Resize the surface horizontally so that it is completely
+	  unconstrained.
+	</description>
+      </entry>
+      <entry name="resize_y" value="32">
+	<description summary="vertically resize the surface">
+	  Resize the surface vertically so that it is completely unconstrained.
 	</description>
       </entry>
     </enum>
@@ -1010,6 +1029,8 @@
 	   summary="x position relative to parent surface window geometry"/>
       <arg name="y" type="int"
 	   summary="y position relative to parent surface window geometry"/>
+      <arg name="width" type="int" summary="window geometry width"/>
+      <arg name="height" type="int" summary="window geometry height"/>
     </event>
 
     <event name="popup_done">