Tree Grid - Lazy loading for children level rows

[evan]

Currently TreeGrid only supports lazy loading for root level rows, so it becomes slow when we have large number of children rows(since they will all be rendered at one time).

The enhancement applies the virtual scrolling model to all children level rows so even we have large number of children rows, it's working pretty well.

[bill]

patch from Evan

[bill]

Uploaded patch from Evan, he says:

Please try dojox/grid/test_treegrid_children_lazyloading.html for a quick try.

Also this patch works pretty well with server-side store(with flatten items and some simple protocol - doc to be added)

TODO items:

1. Add full support for client-side stores that follows standard dojo.data api
2. Add doc to campus doc page

[evan]

An updated patch version is in progress trying to simplify the specific protocol to be more compatible with existing Tree,TreeGrid? - so ideally, the same store would be working with existing Tree, TreeGrid? and the new lazy loading TreeGrid?

The UI still look the same as "treegrid-#11716-09102010.patch"

[Douglas Hays]

(In [23078]) Fixes #11716. Proxy commit for evan (CCLA). Adds lazy loading TreeGrid? support of nonroot rows, and the corresponding testcase.

[evan]

The above "lazy-treegrid.patch" fixed following issues:

1. A conflict occurs when multiple respond from server side and may cause LazyTreeGrid? would be rendered improperly
   

2. Unable to expand a row manually using keyboard
   

3. LazyTreeGrid? content became blank after refreshed/column reordered/column size changed/page size changed
   

4. LazyTreeGrid? won't be rendered correctly after add/delete item(s)
   

5. Sorting property should be sent to server side when fetching children items

[evan]

Note: The "lazy-treegrid.patch" is re-appended to a new ticket #12063

[Douglas Hays]

(In [23301]) Fixes #12063, refs #11716. Proxy commit for evan (IBM, CCLA). Various LazyTreeGrid? bug fixes.

[evan]

(In [23706]) Refs #11716, coding style fix, use mixin() for func overwriting,

[evan]

(In [25463]) Refs #11716 by safely remove expando class for row without any children