Revise the placement example.

README.md

@@ -97,7 +97,7 @@ For `new_placement_cb` the arguments are:
 The callback places the new client by changing its geometry and client data.
 Note that after the callback machi will validate the geometry and fit into the areas.
 So no need to set the `.area`, `.lu`, or `.rd` field of the client data in the callback.
-See `placement.fair` in `layout.lua` for an example.
+See `placement.empty_then_fair` in `layout.lua` for an example.
 
 ## The layout editor and commands
 

layout.lua

@@ -493,7 +493,7 @@ end
 
 module.placement = {}
 
-function module.placement.fair(c, instance, areas, geometry)
+function module.placement.empty_then_fair(c, instance, areas, geometry)
     local area_client_count = {}
     for _, oc in ipairs(c.screen.tiled_clients) do
         local cd = instance.client_data[oc]
@@ -501,18 +501,28 @@ function module.placement.fair(c, instance, areas, geometry)
             area_client_count[cd.area] = (area_client_count[cd.area] or 0) + 1
         end
     end
-    local emptyness_max = nil
+    local choice_client_count = nil
+    local choice_spare_score = nil
     local choice = nil
     for i = 1, #areas do
         local a = areas[i]
         if a.habitable then
-            local emptyness = a.width * a.height / ((area_client_count[i] or 0) + 1)
-            if emptyness_max == nil or emptyness > emptyness_max then
-                emptyness_max = emptyness
+            -- +1 for the new client
+            local client_count = (area_client_count[i] or 0) + 1
+            local spare_score = a.width * a.height / client_count
+            if choice == nil or (choice_client_count > 1 and client_count == 1) then
+                choice_client_count = client_count
+                choice_spare_score = spare_score
+                choice = i
+            elseif (choice_client_count > 1) == (client_count > 1) and  choice_spare_score < spare_score then
+                choice_client_count = client_count
+                choice_spare_score = spare_score
                 choice = i
             end
         end
     end
+    instance.client_data[c].lu = choice
+    instance.client_data[c].rd = choice
     instance.client_data[c].area = choice
     geometry.x = areas[choice].x
     geometry.y = areas[choice].y