{"id":97525,"date":"2017-12-05T07:00:00","date_gmt":"2017-12-05T22:00:00","guid":{"rendered":"https:\/\/blogs.msdn.microsoft.com\/oldnewthing\/?p=97525"},"modified":"2019-03-13T01:20:49","modified_gmt":"2019-03-13T08:20:49","slug":"20171205-00","status":"publish","type":"post","link":"https:\/\/devblogs.microsoft.com\/oldnewthing\/20171205-00\/?p=97525","title":{"rendered":"Tree view check boxes: The extended check box states"},"content":{"rendered":"

Version 6 of the common controls in Windows Vista introduced some new check-box-related extended styles for the tree view controls. Unfortunately, the documentation for them<\/a> is kind of spare. <\/p>\n

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TVS_<\/code>EX_<\/code>PARTIAL­CHECK­BOXES<\/code> <\/dt>\n
Include partial checkbox state if the control has the TVS_<\/code>CHECK­BOXES<\/code> style. <\/dd>\n
TVS_<\/code>EX_<\/code>DIMMED­CHECK­BOXES<\/code> <\/dt>\n
Include dimmed checkbox state if the control has the TVS_<\/code>CHECK­BOXES<\/code> style. <\/dd>\n
TVS_<\/code>EX_<\/code>EXCLUSION­CHECK­BOXES<\/code> <\/dt>\n
Include exclusion checkbox state if the control has the TVS_<\/code>CHECK­BOXES<\/code> style. <\/dd>\n<\/dl>\n<\/blockquote>\n

Yeah, that doesn’t really explain anything. <\/p>\n

Fortunately, more information about what these check box states are for can be found in the documentation for the NSTCSTYLE<\/code> enumeration<\/a>. <\/p>\n

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NSTCS_<\/code>PARTIAL­CHECK­BOXES<\/code> <\/dt>\n
Adds a checkbox icon on the leftmost side of a given item with a square in the center, that indicates that the node is partially selected. Maps to the TVS_<\/code>EX_<\/code>PARTIAL­CHECK­BOXES<\/code> tree view control style. <\/dd>\n
NSTCS_<\/code>DIMMED­CHECK­BOXES<\/code> <\/dt>\n
Adds a checkbox icon on the leftmost side of a given item that contains an icon of a dimmed check mark, that indicates that a node is selected because its parent is selected. Maps to the TVS_<\/code>EX_<\/code>DIMMED­CHECK­BOXES<\/code> tree view control style. <\/dd>\n
NSTCS_<\/code>EXCLUSION­CHECK­BOXES<\/code> <\/dt>\n
Adds a checkbox icon on the leftmost side of a given item that contains a red X<\/b>, which indicates that the item is excluded from the current selection. Without this exclusion icon, selection of a parent item includes selection of its child items. Maps to the TVS_<\/code>EX_<\/code>EXCLUSION­CHECK­BOXES<\/code> tree view control style. <\/dd>\n<\/dl>\n<\/blockquote>\n

Okay, so that explains what the intended purposes of these new styles are. <\/p>\n

Of course, when you use those state images, you can use them to mean whatever you like. Though for consistency with the rest of Windows, you probably want to use them to mean what Windows uses them to mean, just like you should probably use the checked state to mean, y’know, that the thing is selected. <\/p>\n

Don’t forget that these are tree view extended styles, not window manager extended styles, so you set them by using the TVM_<\/code>SET­EXTENDED­STYLE<\/code> message or the corresponding Tree­View_<\/code>Set­Extended­Style<\/code> macro. <\/p>\n

The documentation for these extended styles says that they must be combined with TVS_<\/code>CHECK­BOXES<\/code>, but that is not true; these extended styles imply TVS_<\/code>CHECK­BOXES<\/code>; you don’t need to set TVS_<\/code>CHECK­BOXES<\/code>. In fact, it’s worse than that. If you set TVS_<\/code>CHECK­BOXES<\/code> first, and then set the extended styles second, you won’t get the extended styles at all. That’s because of the rules we spelled out last time: <\/p>\n

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