Type: Boolean
Availability: Read or write at any time
The hasPlusMinus property controls the type of display for the ListBox control or the ComboBox control, by specifying whether the plus/minus images are displayed. The default value is false.
Each list entry in the control can be made up of the following parts.
TreeLines
Plus/Minus
Pictures
Item picture
Text
TreeLines are lines drawn between items in the hierarchy, to display the parents of an item and its siblings.
Plus/Minus is a bitmap or icon that is displayed when the entry has subitems. The image represents the expanded or collapsed state of that part of the hierarchy. A suitable bitmap or icon can be assigned to each of the picturePlus and pictureMinus properties for this part of the display. The default value is a plus (+) and minus (-) sign.
Pictures is an icon or bitmap that represents whether the list entry is a leaf (that is, it has no subentries) or is an expanded or collapsed entry. A suitable bitmap or icon can be assigned to the pictureClosed, pictureOpen, and pictureLeaf properties for this part of the display. The default value is a closed folder, open folder, and a document.
The parts of the display are optional. The hasPlusMinus, hasTreeLines, and hasPictures properties control these parts of the list. If the pictures are larger than the list line size, they are scaled to fit.
Clicking the treeline, plus/minus, or picture area of the display generates a pictureClick event. Logic must then expand or collapse the item, as required. As this process is not automatic, the expand or collapse process can be controlled by the user. For example, the subentries may not be loaded into the list box until an entry is expanded.
By default, the appropriate picture icon is displayed. Setting the itemPictureType property can also manually control the type of picture. When the itemPictureType property is set for an item, no further automatic picture assignment is performed based on expand, collapse, or subitems.
The type of image displayed for the plus/minus display is always automatic. If you want to use these images with user control, set the picture properties to these icons.
To cause the pictureDblClick event, double-click any portion of an entry to the left of the text.
Setting the sorted property for a list box control sets the hasPictures, hasPlusMinus, and hasTreeLines properties to false.
To select the list entry (to set the listIndex property), the text portion of the entry must be clicked or the arrow keys used.