tag: Add a request::layouts signal and append/remove layout.

lib/awful/layout/init.lua

@@ -259,6 +259,8 @@ end
 
 --- Remove a layout from the list of default layouts.
 --
+-- @DOC_text_awful_layout_remove_EXAMPLE@
+--
 -- @staticfct awful.layout.remove_default_layout
 -- @tparam layout to_remove A valid tag layout.
 -- @treturn boolean True if the layout was found and removed.
@@ -455,13 +457,27 @@ local mt = {
     end,
     __newindex = function(_, key, value)
         if key == "layouts" then
-            gdebug.print_warning(
-                "`awful.layout.layouts` was set before `request::default_layouts` could "..
-                "be called. Please use `awful.layout.append_default_layouts` to "..
-                " avoid this problem"
-            )
-            capi.tag.disconnect_signal("new", init_layouts)
-            init_layouts = nil
+            assert(type(value) == "table", "`awful.layout.layouts` needs a table.")
+
+            -- Do not ask for layouts if they were already provided.
+            if init_layouts then
+                gdebug.print_warning(
+                    "`awful.layout.layouts` was set before `request::default_layouts` could "..
+                    "be called. Please use `awful.layout.append_default_layouts` to "..
+                    " avoid this problem"
+                )
+
+                capi.tag.disconnect_signal("new", init_layouts)
+                init_layouts = nil
+            elseif #default_layouts > 0 then
+                gdebug.print_warning(
+                    "`awful.layout.layouts` was set after `request::default_layouts` was "..
+                    "used to get the layouts. This is probably an accident. Use "..
+                    "`awful.layout.remove_default_layout` to get rid of this warning."
+                )
+            end
+
+            default_layouts = value
         else
             rawset(layout, key, value)
         end

lib/awful/tag.lua

@@ -867,6 +867,22 @@ function tag.object.get_layouts(self)
 
     local cls = custom_layouts(self)
 
+    -- Request some layouts. Maybe a new module was added?
+    if #cls == 0 and not tag.getproperty(self, "_layouts_requested") then
+        tag.setproperty(self, "_layouts_requested", true)
+        local old_count = #cls
+        self:emit_signal("request::layouts", "awful", {})
+
+        -- When request::layouts is used, assume it takes precedence over
+        -- the fallback.
+        if #cls > old_count then
+            tag.setproperty(self, "_layouts", gtable.clone(cls, false))
+            return tag.getproperty(self, "_layouts")
+        end
+
+        return tag.object.get_layouts(self)
+    end
+
     -- Without the clone, the custom_layouts would grow
     return #cls > 0 and gtable.merge(gtable.clone(cls, false), alayout.layouts) or
         alayout.layouts
@@ -882,6 +898,60 @@ function tag.object.set_layouts(self, layouts)
     self:emit_signal("property::layouts")
 end
 
+function tag.object.append_layout(self, layout)
+    -- If the layouts are manually modified, don't request more.
+    tag.setproperty(self, "_layouts_requested", true)
+
+    local cls = tag.getproperty(self, "_layouts")
+
+    if not cls then
+        cls = custom_layouts(self)
+    end
+
+    table.insert(cls, layout)
+    self:emit_signal("property::layouts")
+end
+
+function tag.object.append_layouts(self, layouts)
+    -- If the layouts are manually modified, don't request more.
+    tag.setproperty(self, "_layouts_requested", true)
+
+    local cls = tag.getproperty(self, "_layouts")
+
+    if not cls then
+        cls = custom_layouts(self)
+    end
+
+    for _, l in ipairs(layouts) do
+        table.insert(cls, l)
+    end
+    self:emit_signal("property::layouts")
+end
+
+function tag.object.remove_layout(self, layout)
+    local cls = tag.getproperty(self, "_layouts")
+
+    if not cls then
+        cls = custom_layouts(self)
+    end
+
+    local pos = {}
+    for k, l in ipairs(cls) do
+        if l == layout then
+            table.insert(pos, k)
+        end
+    end
+
+    if #pos > 0 then
+        for i=#pos, 1, -1 do
+            table.remove(cls, i)
+        end
+        self:emit_signal("property::layouts")
+    end
+
+    return #pos > 0
+end
+
 function tag.object.get_layout(t)
     local l = tag.getproperty(t, "layout")
     if l then return l end

objects/tag.c

@@ -220,6 +220,15 @@
  * @see awful.layout.remove_default_layout
  */
 
+/** This signals is emitted when a tag needs layouts for the first time.
+ *
+ * If no handler implement it, it will fallback to the content added by
+ * `request::default_layouts`
+ *
+ * @signal request::layouts
+ * @tparam string context The context (currently always "awful").
+ * @tparam table hints A, currently empty, table with hints.
+ */
 
 /** When a client gets tagged with this tag.
  * @signal tagged

tests/examples/text/awful/layout/remove.lua

@@ -0,0 +1,23 @@
+--DOC_GEN_OUTPUT --DOC_HIDE
+local awful = { layout = require("awful.layout"), --DOC_HIDE
+                suit= require("awful.layout.suit")} --DOC_HIDE
+
+awful.layout.append_default_layouts({
+    awful.layout.suit.floating,
+    awful.layout.suit.tile,
+    awful.layout.suit.max,
+})
+
+for _, l in ipairs(awful.layout.layouts) do
+    print("Before:", l.name)
+end
+
+--DOC_NEWLINE
+
+awful.layout.remove_default_layout(awful.layout.suit.tile)
+
+--DOC_NEWLINE
+
+for _, l in ipairs(awful.layout.layouts) do
+    print("After:", l.name)
+end

tests/examples/text/awful/layout/remove.output.txt

@@ -0,0 +1,5 @@
+Before:	floating
+Before:	tile
+Before:	max
+After:	floating
+After:	max