From c94549217613281e86565946149bb9cf3b3c67b9 Mon Sep 17 00:00:00 2001
From: Uli Schlachter <psychon@znc.in>
Date: Sun, 26 Jul 2015 17:03:10 +0200
Subject: [PATCH] Keep client order across restarts

This saves the order of clients in a property called AWESOME_CLIENT_ORDER on the
root window during shutdown. During startup, after managing all existing
windows, we force the client list into the order described by this property
(overwriting any changes that Lua possibly did).

This code should safely handle cases where the property doesn't contain all
existing clients or contains a client which doesn't exist anymore.

Signed-off-by: Uli Schlachter <psychon@znc.in>
---
 awesome.c         | 51 +++++++++++++++++++++++++++++++++++++++++++++++
 common/atoms.list |  1 +
 2 files changed, 52 insertions(+)

diff --git a/awesome.c b/awesome.c
index 6b7726f1..786ff3f1 100644
--- a/awesome.c
+++ b/awesome.c
@@ -85,6 +85,19 @@ awesome_atexit(bool restart)
                 (*c)->geometry.x, (*c)->geometry.y);
     }
 
+    if (restart)
+    {
+        /* Save the client order across restarts */
+        xcb_window_t *wins = p_alloca(xcb_window_t, globalconf.clients.len);
+        int n = 0;
+        foreach(client, globalconf.clients)
+            wins[n++] = (*client)->window;
+
+        xcb_change_property(globalconf.connection, XCB_PROP_MODE_REPLACE,
+                            globalconf.screen->root,
+                            AWESOME_CLIENT_ORDER, XCB_ATOM_WINDOW, 32, n, wins);
+    }
+
     a_dbus_cleanup();
 
     systray_cleanup();
@@ -109,6 +122,36 @@ awesome_atexit(bool restart)
     xcb_disconnect(globalconf.connection);
 }
 
+/** Restore the client order after a restart */
+static void
+restore_client_order(xcb_get_property_cookie_t prop_cookie)
+{
+    int client_idx = 0;
+    xcb_window_t *windows;
+    xcb_get_property_reply_t *reply;
+
+    reply = xcb_get_property_reply(globalconf.connection, prop_cookie, NULL);
+    if (!reply || reply->format != 32 || reply->value_len == 0) {
+        p_delete(&reply);
+        return;
+    }
+
+    windows = xcb_get_property_value(reply);
+    for (uint32_t i = 0; i < reply->value_len; i++)
+        /* Find windows[i] and swap it to where it belongs */
+        foreach(c, globalconf.clients)
+            if ((*c)->window == windows[i])
+            {
+                client_t *tmp = *c;
+                *c = globalconf.clients.tab[client_idx];
+                globalconf.clients.tab[client_idx] = tmp;
+                client_idx++;
+            }
+
+    luaA_class_emit_signal(globalconf_get_lua_State(), &client_class, "list", 0);
+    p_delete(&reply);
+}
+
 /** Scan X to find windows to manage.
  */
 static void
@@ -119,6 +162,7 @@ scan(xcb_query_tree_cookie_t tree_c)
     xcb_window_t *wins = NULL;
     xcb_get_window_attributes_reply_t *attr_r;
     xcb_get_geometry_reply_t *geom_r;
+    xcb_get_property_cookie_t prop_cookie;
     long state;
 
     tree_r = xcb_query_tree_reply(globalconf.connection,
@@ -128,6 +172,11 @@ scan(xcb_query_tree_cookie_t tree_c)
     if(!tree_r)
         return;
 
+    /* This gets the property and deletes it */
+    prop_cookie = xcb_get_property_unchecked(globalconf.connection, true,
+                          globalconf.screen->root, AWESOME_CLIENT_ORDER,
+                          XCB_ATOM_WINDOW, 0, UINT_MAX);
+
     /* Get the tree of the children windows of the current root window */
     if(!(wins = xcb_query_tree_children(tree_r)))
         fatal("cannot get tree children");
@@ -171,6 +220,8 @@ scan(xcb_query_tree_cookie_t tree_c)
     }
 
     p_delete(&tree_r);
+
+    restore_client_order(prop_cookie);
 }
 
 static void
diff --git a/common/atoms.list b/common/atoms.list
index 76c9cbaf..71c57522 100644
--- a/common/atoms.list
+++ b/common/atoms.list
@@ -62,3 +62,4 @@ WM_WINDOW_ROLE
 WM_CLIENT_LEADER
 XSEL_DATA
 WM_TAKE_FOCUS
+AWESOME_CLIENT_ORDER