Update TODO.md

TODO.md

@@ -45,7 +45,21 @@ https://zhuanlan.zhihu.com/p/33778843
 
 #### Before 1.0
 - [ ] Redesign ToolstripMenu so that toolstrip items can be managed by an item source
-  - Consider about <Repeat> with IObservableList^
+  - [ ] `GuiToolstripCollection` remove the space of an item if its `Visible` property is false
+  - [ ] `GuiToolstripGroupContainer` insert splitters between items
+    - `Direction` and `SplitterTemplate` property
+    - `<MenuItemGroups>`, `<ToolstripItemGroups>`
+  - [ ] `GuiToolstripGroup` insert multiple items in one control
+    - `Direction` and `ToolstripItems` (default) property
+    - `AutoVisible` property (set to true (default) will keep `Visible = ToolstripItems.Count() > 0`)
+    - `<MenuItemGroup>`, `<ToolstripItemGroup>` (set `Direction` property)
+  - [ ] `GuiToolstripGroupBinder`
+    - `ItemTemplate` and `Commands` property
+    - `OwnCommands` constructor argument, set to true so that
+      - The binder will maintain lifecycles for commands
+      - The binder will register / unregister commands
+    - `ToolstripGroup` property
+    - `<MenuItemGroupBinder>`, `<ToolstripItemGroupBinder>` (set `ItemTemplate` property)
 - [ ] Real visual state: different layouts / different images in different sizes
 - [ ] Add and query services from controls
 - [ ] Demos: DocumentEditor