SAMPLE: TvwState.exe Simulates Multiple-Selection TreeView Ctrl

ID: Q125587

The information in this article applies to:

Microsoft Win32 Software Development Kit (SDK)

SUMMARY

The TvwState.exe sample demonstrates how to simulate a multiple-selection TreeView control. The Windows 95 TreeView control does not support multiple selection. If you want a multiple-selection TreeView, you can use state images to simulate it in your application.

The TVWSTATE sample accomplishes this by using a checkbox type of state image to indicate that the item is selected or cleared (de-selected). These checkboxes will retain their state even if the TreeView loses focus.

MORE INFORMATION

The following file is available for download from the Microsoft Software Library:

 ~ TvwState.exe (size: 49318 bytes)

For more information about downloading files from the Microsoft Software Library, please see the following article in the Microsoft Knowledge Base:

   ARTICLE-ID: Q119591
   TITLE     : How to Obtain Microsoft Support Files from
               Online Services

The multiple-selection TreeView control simulation is implemented by setting the state image list of the TreeView control to an image list that contains the checked and unchecked checkbox bitmaps. This image list is set by using the TVM_SETIMAGELIST message with lParam == TVSIL_STATE (see InitImageList in TVWSTATE.C). A TreeView control can have two image lists, a normal image list and a state image list. In the TreeView, the display order from left to right is: the expansion button, the state image (if present), the normal image (if present), and then the item text.

When processing the WM_NOTIFY message where (LPNMHDR)lParam->code == NM_CLICK (see MsgNotifyTreeView in TVWSTATE.C), the code checks to see if the user clicked the left mouse button in the checkbox. If this is the case, the state image index of the item is retrieved, the index is toggled between the checked and unchecked image list items, and then the new index is saved.

The state image index identifies which member of the state image list should be displayed. The state image index is stored in bits 12-16 of the item state value. Either TVIS_STATEIMAGEMASK or TVIS_USERMASK can be used to mask off the lower bits. To access just the state image index, use a statement similar to this:

   StateIndex = tvi.state & TVIS_STATEIMAGEMASK;

The INDEXTOSTATEIMAGEMASK macro offsets a value to the correct bits for the state image index. This is accomplished by shifting the given value left 12 places. If the desired state image index is 1, the state can be set using a statement similar to this:

   tvi.state = INDEXTOSTATEIMAGEMASK(1);

This sample can also be modified to implement selection methods similar to those of an extended-selection listbox where the user uses the SHIFT key to select a range of items and/or the CTRL key to select or clear individual items.

Additional query words: Keywords : kbfile kbsample kbCtrl kbNTOS351 kbNTOS400 kbSDKWin32 kbTreeView kbGrpUser kbWinOS95 kbWinOS98

Last Reviewed: January 2, 1999