Tree Control Styles
Tree control (CTreeCtrl) styles govern aspects of a tree control's appearance. You set the initial styles when you create the tree control. You can retrieve and change the styles after creating the tree control by using the GetWindowLong and SetWindowLong Windows functions, specifying GWL_STYLE for the nIndex parameter. For a complete list of styles, see Tree View Control Window Styles in the Windows SDK.
The TVS_HASLINES style enhances the graphic representation of a tree control's hierarchy by drawing lines that link child items to their corresponding parent item. This style does not link items at the root of the hierarchy. To do so, you need to combine the TVS_HASLINES and TVS_LINESATROOT styles.
The user can expand or collapse a parent item's list of child items by double-clicking the parent item. A tree control that has the TVS_SINGLEEXPAND style causes the item being selected to expand and the item being unselected to collapse. If the mouse is used to single-click the selected item and that item is closed, it will be expanded. If the selected item is single-clicked when it is open, it will be collapsed.
A tree control that has the TVS_HASBUTTONS style adds a button to the left side of each parent item. The user can click the button to expand or collapse the child items as an alternative to double-clicking the parent item. TVS_HASBUTTONS does not add buttons to items at the root of the hierarchy. To do so, you must combine TVS_HASLINES, TVS_LINESATROOT, and TVS_HASBUTTONS.
The TVS_EDITLABELS style makes it possible for the user to edit the labels of tree control items. For more information about editing labels, see Tree Control Label Editing later in this topic.
The TVS_NOTOOLTIPS style disables the automatic tool tip feature of tree view controls. This feature automatically displays a tool tip, containing the title of the item under the mouse cursor, if the entire title is not currently visible.