Functionality for deleting a tag using awful.tag.

tag.delete(t, fb):
    Delete tags if certain criteria are met:
        - There are no clients assigned exclusively to this tag.
        - Stickied clients have somewhere to go, 'fb' the fallback tag

    If after deleting there is no tag selected then try and
    history.restore() or select the first tag on the screen.

    Return true if successful and nil otherwise.

Signed-off-by: Perry Hargrave <perry.hargrave@gmail.com>
Signed-off-by: Ignas Anikevicius <anikevicius@gmail.com>
Signed-off-by: Uli Schlachter <psychon@znc.in>

lib/awful/tag.lua.in

@@ -96,6 +96,74 @@ function new(names, screen, layout)
     return tags
 end
 
+--- Find a suitable fallback tag.
+-- @param screen The screen number to look for a tag on. [mouse.screen]
+-- @param target A table of tags we consider unacceptable. [selectedlist(scr)]
+function find_fallback(screen, invalids)
+    local scr = screen or capi.mouse.screen
+    local t = invalids or selectedlist(scr)
+
+    for _, v in pairs(capi.screen[scr]:tags()) do
+        if not util.table.hasitem(t, v) then return v end
+    end
+end
+
+--- Delete a tag.
+-- @param target_tag Optional tag object to delete. [selected()]
+-- @param fallback_tag Tag to assign stickied tags to. [~selected()]
+-- @return Returns true if the tag is successfully deleted, nil otherwise.
+-- If there are no clients exclusively on this tag then delete it. Any
+-- stickied clients are assigned to the optional 'fallback_tag'.
+-- If after deleting the tag there is no selected tag, try and restore from
+-- history or select the first tag on the screen.
+function delete(target_tag, fallback_tag)
+    -- abort if no tag is passed or currently selected
+    local target_tag = target_tag or selected()
+    if target_tag == nil then return end
+
+    local ntags = #capi.screen[target_tag.screen]:tags()
+    local target_scr = target_tag.screen
+
+    -- We can't use the target tag as a fallback.
+    local fallback_tag = fallback_tag
+    if fallback_tag == target_tag then return end
+
+    -- No fallback_tag provided, try and get one.
+    if fallback_tag == nil then
+        fallback_tag = find_fallback(target_scr, {target_tag})
+    end
+
+    -- Abort if we would have un-tagged clients.
+    local clients = target_tag:clients()
+    if ( #clients > 0 and ntags <= 1 ) or fallback_tag == nil then return end
+
+    -- Move the clients we can off of this tag.
+    for _, c in pairs(clients) do
+
+        -- If a client has only this tag, or stickied clients with
+        -- nowhere to go, abort.
+        if (not c.sticky and #c:tags() == 1) or
+                                    (c.sticky and fallback_tag == nil) then
+            return
+        else
+            c:tags({fallback_tag})
+        end
+    end
+
+    -- delete the tag
+    target_tag.screen = nil
+
+    -- If no tags are visible, try and view one.
+    if selected(target_scr) == nil and ntags > 0 then
+        history.restore()
+        if selected(target_scr) == nil then
+            capi.screen[target_scr]:tags()[1].selected = true
+        end
+    end
+
+    return true
+end
+
 --- Update the tag history.
 -- @param obj Screen object.
 function history.update(obj)