xdg-shell: Add set_margin request

This is used to figure out the size of "invisible" decorations, which we'll
use to better know the visible extents of the surface, which we can use for
constraining, titlebars, and more.

1 files changed, 26 insertions, 0 deletions

diff --git a/protocol/xdg-shell.xml b/protocol/xdg-shell.xml
index 5c21f4eb..f0d04aa3 100644
--- a/protocol/xdg-shell.xml
+++ b/protocol/xdg-shell.xml
@@ -124,6 +124,32 @@
       <arg name="parent" type="object" interface="wl_surface" allow-null="true"/>
     </request>
 
+    <request name="set_margin">
+      <description summary="set the visible frame boundaries">
+        This tells the compositor what the visible size of the window
+        should be, so it can use it to determine what borders to use for
+        constrainment and alignment.
+
+        CSD often has invisible areas for decoration purposes, like drop
+        shadows. These "shadow" drawings need to be subtracted out of the
+        normal boundaries of the window when computing where to place
+        windows (e.g. to set this window so it's centered on top of another,
+        or to put it to the left or right of the screen.)
+
+        This value should change as little as possible at runtime, to
+        prevent flicker.
+
+        This value is also ignored when the window is maximized or
+        fullscreen, and assumed to be 0.
+
+        If never called, this value is assumed to be 0.
+      </description>
+      <arg name="left_margin" type="int"/>
+      <arg name="right_margin" type="int"/>
+      <arg name="top_margin" type="int"/>
+      <arg name="bottom_margin" type="int"/>
+    </request>
+
     <request name="set_title">
       <description summary="set surface title">
 	Set a short title for the surface.