add events: view_opened and view_closed (#965)

* add events: view_opened and view_closed

* fix typos

* rename view -> menu

doc/cmp.txt

@@ -222,6 +222,10 @@ NOTE: `<Cmd>lua require('cmp').complete()<CR>` can be used to call these functio
 
   - `complete_done`: emit after current completion is done.
   - `confirm_done`: emit after confirmation is done.
+  - `menu_opened`: emit after opening a new completion menu. Called with a table holding a key
+    named `window`, pointing to the completion menu implementation.
+  - `menu_closed`: emit after completion menu is closed. Called with a table holding a key
+    named `window`, pointing to the completion menu implementation.
 
 ==============================================================================
 Mapping                                                            *cmp-mapping*

lua/cmp/core.lua

@@ -34,9 +34,11 @@ core.new = function()
   self.view.event:on('keymap', function(...)
     self:on_keymap(...)
   end)
-  self.view.event:on('complete_done', function(evt)
-    self.event:emit('complete_done', evt)
-  end)
+  for _, event_name in ipairs({ 'complete_done', 'menu_opened', 'menu_closed' }) do
+    self.view.event:on(event_name, function(evt)
+      self.event:emit(event_name, evt)
+    end)
+  end
   return self
 end
 

lua/cmp/view.lua

@@ -108,6 +108,9 @@ view.open = function(self, ctx, sources)
     -- open
     if #entries > 0 then
       self:_get_entries_view():open(offset, entries)
+      self.event:emit('menu_opened', {
+        window = self:_get_entries_view(),
+      })
       break
     end
   end
@@ -128,6 +131,9 @@ view.close = function(self)
   self:_get_entries_view():close()
   self.docs_view:close()
   self.ghost_text_view:hide()
+  self.event:emit('menu_closed', {
+    window = self:_get_entries_view(),
+  })
 end
 
 ---Abort menu
@@ -135,6 +141,9 @@ view.abort = function(self)
   self:_get_entries_view():abort()
   self.docs_view:close()
   self.ghost_text_view:hide()
+  self.event:emit('menu_closed', {
+    window = self:_get_entries_view(),
+  })
 end
 
 ---Return the view is visible or not.