client: Rewrite the client stacking code in Lua.

This adds 2 new requests:

 * request::raise: Helps to decouple ewmh and client class
    internally plus allow some focus stealing policies.
 * reqest::restack: Send *why* something is restacked to Lua. It
    allows to do things like sending a client to the back of a
    layout rather than use the master area.

This is mostly a 1:1 port of the C code. The idea is to use this as
a starting point to have a stack per `tag` rather than something
global. It also paves the way for stacking wibox among clients
in a predictable way. None of that is exposed in the public API
as part of this commit. The point is to get enough going so the
wibox desktop layer PR can be implemented on top of this.

event.c

@@ -830,8 +830,14 @@ event_handle_maprequest(xcb_map_request_event_t *ev)
             luaA_object_push(L, c);
             client_set_minimized(L, -1, false);
             lua_pop(L, 1);
-            /* it will be raised, so just update ourself */
-            client_raise(c);
+
+            lua_pushstring(L, "maprequest");
+            lua_newtable(L);
+            lua_pushstring(L, "client");
+            luaA_object_push(L, c);
+            lua_rawset(L, -3);
+
+            luaA_object_emit_signal(L, -3, "request::raise", 2);
         }
     }
     else

event.h

@@ -46,7 +46,6 @@ awesome_refresh(void)
     drawin_refresh();
     client_refresh();
     banning_refresh();
-    stack_refresh();
     client_destroy_later();
     return xcb_flush(globalconf.connection);
 }

lib/awful/layout/init.lua

@@ -34,11 +34,13 @@
 local ipairs = ipairs
 local type = type
 local capi = {
-    screen = screen,
-    mouse  = mouse,
+    screen  = screen,
+    mouse   = mouse,
     awesome = awesome,
-    client = client,
-    tag = tag
+    client  = client,
+    drawin  = drawin,
+    tag     = tag,
+    root    = root,
 }
 local tag = require("awful.tag")
 local client = require("awful.client")
@@ -55,6 +57,9 @@ end
 
 local layout = {}
 
+-- Avoid restacking the clients and drawins too often.
+local need_restack = true
+
 -- Support `table.insert()` to avoid breaking old code.
 local default_layouts = setmetatable({}, {
     __newindex = function(self, key, value)
@@ -64,6 +69,17 @@ local default_layouts = setmetatable({}, {
     end
 })
 
+local x11_layers_ordered, x11_layers_keys = {
+    "WINDOW_LAYER_IGNORE",
+    "WINDOW_LAYER_DESKTOP",
+    "WINDOW_LAYER_BELOW",
+    "WINDOW_LAYER_NORMAL",
+    "WINDOW_LAYER_ABOVE",
+    "WINDOW_LAYER_FULLSCREEN",
+    "WINDOW_LAYER_ONTOP"
+}, {}
+
+for k, v in ipairs(x11_layers_ordered) do x11_layers_keys[v] = k end
 
 layout.suit = require("awful.layout.suit")
 
@@ -108,6 +124,27 @@ local arrange_lock = false
 -- Delay one arrange call per screen.
 local delayed_arrange = {}
 
+local function client_to_layer(o)
+    if o.type == "desktop" then
+        return x11_layers_keys.WINDOW_LAYER_DESKTOP
+    elseif o.ontop then
+        -- first deal with user set attributes
+        return x11_layers_keys.WINDOW_LAYER_ONTOP;
+    elseif o.fullscreen and capi.client.focus == o then
+        -- Fullscreen windows only get their own layer when they have the focus
+        return x11_layers_keys.WINDOW_LAYER_FULLSCREEN;
+    elseif o.above then
+        return x11_layers_keys.WINDOW_LAYER_ABOVE;
+    elseif o.below then
+        return x11_layers_keys.WINDOW_LAYER_BELOW;
+    elseif o.transient_for then
+        -- check for transient attr
+        return x11_layers_keys.WINDOW_LAYER_IGNORE;
+    else
+        return x11_layers_keys.WINDOW_LAYER_NORMAL
+    end
+end
+
 --- Get the current layout.
 -- @tparam screen screen The screen.
 -- @return The layout function.
@@ -237,6 +274,7 @@ end
 -- @tparam screen screen The screen to arrange.
 -- @noreturn
 -- @staticfct awful.layout.arrange
+-- @see restack
 function layout.arrange(screen)
     screen = get_screen(screen)
     if not screen or delayed_arrange[screen] then return end
@@ -417,8 +455,82 @@ function layout.move_handler(c, context, hints) --luacheck: no unused args
     end
 end
 
+-- [UNDOCUMENTED] Handler for `request::restack`.
+--
+-- @signalhandler awful.layout.move_handler
+-- @tparam string context The context
+-- @tparam table hints Additional hints
+-- @tparam[opt=nil] client|nil hints.client The client
+-- @tparam[opt=nil] drawin|nil hints.drawin Additional hints
+function layout._restack_handler(context, hints) -- luacheck: no unused args
+    --TODO Support permissions
+    need_restack = true
+end
+
+--- Arrange the clients on the Z axis.
+-- @staticfct awful.layout.restack
+-- @noreturn
+-- @see arrange
+function layout.restack()
+
+    local layers = {}
+
+    local function append(o, drawin)
+        local layer = client_to_layer(o)
+        layers[layer] = layers[layer] or {}
+        if drawin then
+            table.insert(layers[layer], o.drawin)
+        else
+            table.insert(layers[layer], 1, o)
+        end
+    end
+
+    for _, c in ipairs(capi.client.get(nil, true)) do append(c) end
+
+    for _, d in ipairs(capi.drawin.get()) do
+        append(d.get_wibox(), true)
+    end
+
+    local result = {}
+
+    for i=#x11_layers_ordered, 1, -1 do
+        if layers[i] then
+            for _, v in ipairs(layers[i] or {}) do
+                table.insert(result, v)
+            end
+        end
+    end
+
+    capi.root.set_stacking_order(result)
+end
+
 capi.client.connect_signal("request::geometry", layout.move_handler)
 
+-- Translate the `request::raise`, which will trigger a  `"request::restack"`.
+capi.client.connect_signal("request::raise", function(c, context, hints) --luacheck: no unused args
+    hints.client:raise()
+end)
+
+capi.client.connect_signal("request::restack", layout._restack_handler)
+
+-- Check if the type is `"desktop"`, which goes below everything.
+for _, class in ipairs(capi.client, capi.drawin) do
+    class.connect_signal("property::type", function(o)
+        capi.client.emit_signal("request::restack", "type", {
+            client = o.modal ~= nil and o or nil,
+            drawin = o.modal == nil and o or nil,
+        })
+    end)
+end
+
+-- Place the clients and drawin on top of each other.
+capi.awesome.connect_signal("refresh", function()
+    if need_restack then
+        layout.restack()
+        need_restack = false
+    end
+end)
+
 -- When a screen is moved, make (floating) clients follow it
 capi.screen.connect_signal("property::geometry", function(s, old_geom)
     local geom = s.geometry

objects/client.c

@@ -2241,7 +2241,7 @@ client_manage(xcb_window_t w, xcb_get_geometry_reply_t *wgeom, xcb_get_window_at
     ewmh_client_check_hints(c);
 
     /* Push client in stack */
-    stack_client_push(c);
+    stack_client_push(L, c, "manage");
 
     /* Request our response */
     xcb_get_property_reply_t *reply =
@@ -2717,7 +2717,7 @@ client_set_fullscreen(lua_State *L, int cidx, bool s)
         luaA_object_emit_signal(L, abs_cidx, "property::fullscreen", 0);
         /* Force a client resize, so that titlebars get shown/hidden */
         client_resize_do(c, c->geometry);
-        stack_windows();
+        stack_windows(L, "fullscreen", c, NULL);
     }
 }
 
@@ -2768,7 +2768,7 @@ client_set_maximized_common(lua_State *L, int cidx, bool s, const char* type, co
         if(max_before != c->maximized)
             luaA_object_emit_signal(L, abs_cidx, "property::maximized", 0);
 
-        stack_windows();
+        stack_windows(L, "maximized", c, NULL);
     }
 }
 
@@ -2816,7 +2816,7 @@ client_set_above(lua_State *L, int cidx, bool s)
             client_set_fullscreen(L, cidx, false);
         }
         c->above = s;
-        stack_windows();
+        stack_windows(L, "above", c, NULL);
         luaA_object_emit_signal(L, cidx, "property::above", 0);
     }
 }
@@ -2841,7 +2841,7 @@ client_set_below(lua_State *L, int cidx, bool s)
             client_set_fullscreen(L, cidx, false);
         }
         c->below = s;
-        stack_windows();
+        stack_windows(L, "below", c, NULL);
         luaA_object_emit_signal(L, cidx, "property::below", 0);
     }
 }
@@ -2859,7 +2859,7 @@ client_set_modal(lua_State *L, int cidx, bool s)
     if(c->modal != s)
     {
         c->modal = s;
-        stack_windows();
+        stack_windows(L, "modal", c, NULL);
         luaA_object_emit_signal(L, cidx, "property::modal", 0);
     }
 }
@@ -2884,7 +2884,7 @@ client_set_ontop(lua_State *L, int cidx, bool s)
             client_set_fullscreen(L, cidx, false);
         }
         c->ontop = s;
-        stack_windows();
+        stack_windows(L, "ontop", c, NULL);
         luaA_object_emit_signal(L, cidx, "property::ontop", 0);
     }
 }
@@ -2942,7 +2942,7 @@ client_unmanage(client_t *c, client_unmanage_t reason)
             client_array_remove(&globalconf.clients, elem);
             break;
         }
-    stack_client_remove(c);
+    stack_client_remove(L, c, false, "unmanage");
     for(int i = 0; i < globalconf.tags.len; i++)
         untag_client(c, globalconf.tags.tab[i]);
 
@@ -3402,7 +3402,29 @@ luaA_client_raise(lua_State *L)
     )
         return 0;
 
-    client_raise(c);
+    client_t *tc = c;
+    int counter = 0;
+
+    /* Find number of transient layers. */
+    for(counter = 0; tc->transient_for; counter++)
+        tc = tc->transient_for;
+
+    /* Push them in reverse order. */
+    for(; counter > 0; counter--)
+    {
+        tc = c;
+        for(int i = 0; i < counter; i++)
+            tc = tc->transient_for;
+        stack_client_append(L, tc, "raise");
+    }
+
+    /* Push c on top of the stack. */
+    stack_client_append(L, c, "raise");
+
+    /* Notify the listeners */
+    luaA_object_push(L, c);
+    luaA_object_emit_signal(L, -1, "raised", 0);
+    lua_pop(L, 1);
 
     return 0;
 }
@@ -3426,11 +3448,11 @@ luaA_client_lower(lua_State *L)
     if (globalconf.stack.len && globalconf.stack.tab[0] == c)
         return 0;
 
-    stack_client_push(c);
+    stack_client_push(L, c, "lower");
 
     /* Traverse all transient layers. */
     for(client_t *tc = c->transient_for; tc; tc = tc->transient_for)
-        stack_client_push(tc);
+        stack_client_push(L, tc, "lower");
 
     /* Notify the listeners */
     luaA_object_push(L, c);

objects/client.h

@@ -258,38 +258,6 @@ drawable_t *client_get_drawable(client_t *, int, int);
 drawable_t *client_get_drawable_offset(client_t *, int *, int *);
 area_t client_get_undecorated_geometry(client_t *);
 
-/** Put client on top of the stack.
- * \param c The client to raise.
- */
-static inline void
-client_raise(client_t *c)
-{
-    client_t *tc = c;
-    int counter = 0;
-
-    /* Find number of transient layers. */
-    for(counter = 0; tc->transient_for; counter++)
-        tc = tc->transient_for;
-
-    /* Push them in reverse order. */
-    for(; counter > 0; counter--)
-    {
-        tc = c;
-        for(int i = 0; i < counter; i++)
-            tc = tc->transient_for;
-        stack_client_append(tc);
-    }
-
-    /* Push c on top of the stack. */
-    stack_client_append(c);
-
-    /* Notify the listeners */
-    lua_State *L = globalconf_get_lua_State();
-    luaA_object_push(L, c);
-    luaA_object_emit_signal(L, -1, "raised", 0);
-    lua_pop(L, 1);
-}
-
 /** Check if a client has fixed size.
  * \param c A client.
  * \return A boolean value, true if the client has a fixed size.

objects/drawin.c

@@ -336,7 +336,7 @@ drawin_map(lua_State *L, int widx)
     /* Deactivate BMA */
     client_restore_enterleave_events();
     /* Stack this drawin correctly */
-    stack_windows();
+    stack_windows(L, "append", NULL, drawin);
     /* Add it to the list of visible drawins */
     drawin_array_append(&globalconf.drawins, drawin);
     /* Make sure it has a surface */
@@ -591,7 +591,7 @@ luaA_drawin_set_ontop(lua_State *L, drawin_t *drawin)
     if(b != drawin->ontop)
     {
         drawin->ontop = b;
-        stack_windows();
+        stack_windows(L, "ontop", NULL, drawin);
         luaA_object_emit_signal(L, -3, "property::ontop", 0);
     }
     return 0;

root.c

@@ -42,6 +42,7 @@
 #include "objects/button.h"
 #include "common/luaclass.h"
 #include "xwindow.h"
+#include "stack.h"
 
 #include "math.h"
 
@@ -653,6 +654,7 @@ const struct luaL_Reg awesome_root_methods[] =
     { "tags", luaA_root_tags },
     { "__index", luaA_root_index },
     { "__newindex", luaA_root_newindex },
+    { "set_stacking_order", luaA_set_stacking_order},
     { "set_index_miss_handler", luaA_root_set_index_miss_handler},
     { "set_call_handler", luaA_root_set_call_handler},
     { "set_newindex_miss_handler", luaA_root_set_newindex_miss_handler},