Switch protocol to using serial numbers for ordering events and requests

The wayland protocol, as X, uses timestamps to match up certain
requests with input events.  The problem is that sometimes we need to
send out an event that doesn't have a corresponding timestamped input
event.  For example, the pointer focus surface goes away and new
surface needs to receive a pointer enter event.  These events are
normally timestamped with the evdev event timestamp, but in this case,
we don't have a evdev timestamp.  So we have to go to gettimeofday (or
clock_gettime()) and then we don't know if it's coming from the same
time source etc.

However for all these cases we don't need a real time timestamp, we
just need a serial number that encodes the order of events inside the
server.  So we introduce a serial number mechanism that we can use to
order events.  We still need real-time timestamps for actual input
device events (motion, buttons, keys, touch), to be able to reason
about double-click speed and movement speed so events that correspond to user input carry both a serial number and a timestamp.

The serial number also give us a mechanism to key together events that
are "logically the same" such as a unicode event and a keycode event,
or a motion event and a relative event from a raw device.

1 files changed, 18 insertions, 15 deletions

diff --git a/protocol/wayland.xml b/protocol/wayland.xml
index 9e95d34..bd3c868 100644
--- a/protocol/wayland.xml
+++ b/protocol/wayland.xml
@@ -109,7 +109,7 @@
 
   <interface name="wl_callback" version="1">
     <event name="done">
-      <arg name="time" type="uint"/>
+      <arg name="serial" type="uint"/>
     </event>
   </interface>
 
@@ -239,7 +239,7 @@
 	NULL for not accepted.  Use for feedback during drag and drop.
       </description>
 
-      <arg name="time" type="uint"/>
+      <arg name="serial" type="uint"/>
       <arg name="type" type="string"/>
     </request>
 
@@ -311,7 +311,7 @@
 	data source that provides the data for the eventual data
 	transfer.  The origin surface is the surface where the drag
 	originates and the client must have an active implicit grab
-	that matches the timestamp.  The icon surface is an optional
+	that matches the serial.  The icon surface is an optional
 	(can be nil) surface that provides an icon to be moved around
 	with the cursor.  Initially, the top-left corner of the icon
 	surface is placed at the cursor hotspot, but subsequent
@@ -320,12 +320,12 @@
       <arg name="source" type="object" interface="wl_data_source"/>
       <arg name="origin" type="object" interface="wl_surface"/>
       <arg name="icon" type="object" interface="wl_surface"/>
-      <arg name="time" type="uint"/>
+      <arg name="serial" type="uint"/>
     </request>
 
     <request name="set_selection">
       <arg name="source" type="object" interface="wl_data_source"/>
-      <arg name="time" type="uint"/>
+      <arg name="serial" type="uint"/>
     </request>
 
     <event name="data_offer">
@@ -343,7 +343,7 @@
     </event>
 
     <event name="enter">
-      <arg name="time" type="uint"/>
+      <arg name="serial" type="uint"/>
       <arg name="surface" type="object" interface="wl_surface"/>
       <arg name="x" type="int"/>
       <arg name="y" type="int"/>
@@ -405,7 +405,7 @@
 
     <request name="move">
       <arg name="input_device" type="object" interface="wl_input_device"/>
-      <arg name="time" type="uint"/>
+      <arg name="serial" type="uint"/>
     </request>
 
     <enum name="resize">
@@ -422,7 +422,7 @@
 
     <request name="resize">
       <arg name="input_device" type="object" interface="wl_input_device"/>
-      <arg name="time" type="uint"/>
+      <arg name="serial" type="uint"/>
       <arg name="edges" type="uint"/>
     </request>
 
@@ -517,7 +517,7 @@
       </description>
 
       <arg name="input_device" type="object" interface="wl_input_device"/>
-      <arg name="time" type="uint"/>
+      <arg name="serial" type="uint"/>
       <arg name="parent" type="object" interface="wl_shell_surface"/>
       <arg name="x" type="int"/>
       <arg name="y" type="int"/>
@@ -547,7 +547,6 @@
 	received.
       </description>
 
-      <arg name="time" type="uint"/>
       <arg name="edges" type="uint"/>
       <arg name="width" type="int"/>
       <arg name="height" type="int"/>
@@ -663,7 +662,7 @@
 	clients surfaces.
       </description>
 
-      <arg name="time" type="uint"/>
+      <arg name="serial" type="uint"/>
       <arg name="buffer" type="object" interface="wl_buffer"/>
       <arg name="hotspot_x" type="int"/>
       <arg name="hotspot_y" type="int"/>
@@ -686,6 +685,7 @@
 	of the click is given by the last motion or pointer_focus event.
       </description>
 
+      <arg name="serial" type="uint"/>
       <arg name="time" type="uint"/>
       <arg name="button" type="uint"/>
       <arg name="state" type="uint"/>
@@ -712,6 +712,7 @@
 	A key was pressed or released.
       </description>
 
+      <arg name="serial" type="uint"/>
       <arg name="time" type="uint"/>
       <arg name="key" type="uint"/>
       <arg name="state" type="uint"/>
@@ -725,7 +726,7 @@
 	event by setting an appropriate pointer image.
       </description>
 
-      <arg name="time" type="uint"/>
+      <arg name="serial" type="uint"/>
       <arg name="surface" type="object" interface="wl_surface"/>
       <arg name="surface_x" type="int"/>
       <arg name="surface_y" type="int"/>
@@ -734,22 +735,23 @@
     <event name="pointer_leave">
       <description summary="pointer leave event">
       </description>
-      <arg name="time" type="uint"/>
+      <arg name="serial" type="uint"/>
       <arg name="surface" type="object" interface="wl_surface"/>
     </event>
 
     <event name="keyboard_enter">
-      <arg name="time" type="uint"/>
+      <arg name="serial" type="uint"/>
       <arg name="surface" type="object" interface="wl_surface"/>
       <arg name="keys" type="array"/>
     </event>
 
     <event name="keyboard_leave">
-      <arg name="time" type="uint"/>
+      <arg name="serial" type="uint"/>
       <arg name="surface" type="object" interface="wl_surface"/>
     </event>
 
     <event name="touch_down">
+      <arg name="serial" type="uint"/>
       <arg name="time" type="uint"/>
       <arg name="surface" type="object" interface="wl_surface"/>
       <arg name="id" type="int" />
@@ -758,6 +760,7 @@
     </event>
 
     <event name="touch_up">
+      <arg name="serial" type="uint"/>
       <arg name="time" type="uint"/>
       <arg name="id" type="int" />
     </event>