Using overlay images

Step 1: Set up the overlay images

The SetOverlayImage() takes two arguments. The first argument is the index of the image within the image list that you want to use as an overlay mask. If you want the third image in the list to be an overlay mask then this value would be 2 and if you want the tenth image, this value would be 9.

The second argument is the one-based index of the overlay mask. This argument can have a value of 1 to 4 inclusive. This serves as the identifier for the overlay mask. If you are using only one image as an overlay mask, you can choose any of the four index it need not be one necessarily. Also, if you call SetOverlayImage() for two different images with the same overlay mask index then the latter call will supercede the previous call.

        m_tree.m_image.SetOverlayImage(15, 1 );
        m_tree.m_image.SetOverlayImage(16, 2 );
        m_tree.m_image.SetOverlayImage(18, 3 );
        m_tree.m_image.SetOverlayImage(20, 4 );

Step 2: Set the item state to use the overlay mask

        // Use third overlay mask
        SetItemState( hItem, INDEXTOOVERLAYMASK(3), TVIS_OVERLAYMASK );

        // Remove overlay mask by using index zero.
        SetItemState( hti, INDEXTOOVERLAYMASK(0), TVIS_OVERLAYMASK );