Checking a Win32 Tree View Item Automatically Checks all Child Items

I am using the Win32 API and MS Visual C++ 6 to build a tree view of a directory structure, wit开发者_如何学编程h check boxes associated with each tree view item. My goal is to be able to check a parent folder, and have that automatically check all of its associated children.

However, after digging through MSDN, I have not been able to find a control notification message for an item being checked, only when an item is selected. I have considered using a selection notification message to prompt the program to poll the item and see if its current 'check state' is true, but I am not sure that checked and selected can be tied together in such a way, and am also concerned about the overhead associated with constantly polling items as a user moves through a very large directory.

Has anyone had experience setting up this scenario? Are my concerns about the overhead of polling a GUI element justified?

There isn't any notification. You can write your own, though. Just handle mouse click and use hittest to see if the mouse cursor is on the state image. For completeness handle the space key and send the same notification for the selected item too.

As of Windows Vista, Microsoft has introduced NM_TVSTATEIMAGECHANGING and a corresponding NMTVSTATEIMAGECHANGING structure. I'm not sure why this is not documented with the Tree View notifications but instead in the General Control Reference section.

This notification code is sent by the tree control when the state image is changing (i.e. when the check box is clicked).

The NMTVSTATEIMAGECHANGING struct has a iOldStateImageIndex and iNewStateImageIndex field that specifies the corresponding change. This information can be used to determine the new state image that will be displayed (1 is the unchecked box and 2 is the checked box)

Vista also introduces dimmed, partial and excluded checks though at the moment I'm not sure how those are represented by the state image index as the two base cases above.

Here is the best way by MSDN (TreeView::AfterCheck Event):

http://msdn.microsoft.com/en-us/library/system.windows.forms.treeview.aftercheck(v=vs.110).aspx