CDragListBox Class

In addition to providing the functionality of a Windows list box, the CDragListBox class allows the user to move list box items, such as filenames, within the list box.

Syntax

class CDragListBox : public CListBox

Members

Public Constructors

Name	Description
CDragListBox::CDragListBox	Constructs a CDragListBox object.

Public Methods

Name	Description
CDragListBox::BeginDrag	Called by the framework when a drag operation starts.
CDragListBox::CancelDrag	Called by the framework when a drag operation has been canceled.
CDragListBox::Dragging	Called by the framework during a drag operation.
CDragListBox::DrawInsert	Draws the insertion guide of the drag list box.
CDragListBox::Dropped	Called by the framework after the item has been dropped.
CDragListBox::ItemFromPt	Returns the coordinates of the item being dragged.

Remarks

List boxes with this capability allow users to order the items in a list in whatever manner is most useful to them. By default, the list box will move the item to the new location in the list. However, CDragListBox objects can be customized to copy items instead of moving them.

The list box control associated with the CDragListBox class must not have the LBS_SORT or the LBS_MULTIPLESELECT style. For a description of list box styles, see List-Box Styles.

To use a drag list box in an existing dialog box of your application, add a list box control to your dialog template using the dialog editor and then assign a member variable (of Category Control and Variable Type CDragListBox) corresponding to the list box control in your dialog template.

For more information on assigning controls to member variables, see Shortcut for Defining Member Variables for Dialog Controls.

Inheritance Hierarchy

CObject

CCmdTarget

CWnd

CListBox

CDragListBox

Requirements

Header: afxcmn.h

CDragListBox::BeginDrag

Called by the framework when an event occurs that could begin a drag operation, such as pressing the left mouse button.

virtual BOOL BeginDrag(CPoint pt);

Parameters

pt
A CPoint object that contains the coordinates of the item being dragged.

Return Value

Nonzero if dragging is allowed, otherwise 0.

Remarks

Override this function if you want to control what happens when a drag operation begins. The default implementation captures the mouse and stays in drag mode until the user clicks the left or right mouse button or presses ESC, at which time the drag operation is canceled.

CDragListBox::CancelDrag

Called by the framework when a drag operation has been canceled.

virtual void CancelDrag(CPoint pt);

Parameters

pt
A CPoint object that contains the coordinates of the item being dragged.

Remarks

Override this function to handle any special processing for your list box control.

CDragListBox::CDragListBox

Constructs a CDragListBox object.

CDragListBox();

CDragListBox::Dragging

Called by the framework when a list box item is being dragged within the CDragListBox object.

virtual UINT Dragging(CPoint pt);

Parameters

pt
A CPoint object that contains the x and y screen coordinates of the cursor.

Return Value

The resource ID of the cursor to be displayed. The following values are possible:

• DL_COPYCURSOR Indicates that the item will be copied.

• DL_MOVECURSOR Indicates that the item will be moved.

• DL_STOPCURSOR Indicates that the current drop target is not acceptable.

Remarks

The default behavior returns DL_MOVECURSOR. Override this function if you want to provide additional functionality.

CDragListBox::DrawInsert

Called by the framework to draw the insertion guide before the item with the indicated index.

virtual void DrawInsert(int nItem);

Parameters

nItem
Zero-based index of the insertion point.

Remarks

A value of - 1 clears the insertion guide. Override this function to modify the appearance or behavior of the insertion guide.

CDragListBox::Dropped

Called by the framework when an item is dropped within a CDragListBox object.

virtual void Dropped(
    int nSrcIndex,
    CPoint pt);

Parameters

nSrcIndex
Specifies the zero-based index of the dropped string.

pt
A CPoint object that contains the coordinates of the drop site.

Remarks

The default behavior copies the list box item and its data to the new location and then deletes the original item. Override this function to customize the default behavior, such as enabling copies of list box items to be dragged to other locations within the list.

CDragListBox::ItemFromPt

Call this function to retrieve the zero-based index of the list box item located at pt.

int ItemFromPt(
    CPoint pt,
    BOOL bAutoScroll = TRUE) const;

Parameters

pt
A CPoint object containing the coordinates of a point within the list box.

bAutoScroll
Nonzero if scrolling is allowed, otherwise 0.

Return Value

Zero-based index of the drag list box item.

See also

MFC Sample TSTCON
CListBox Class
Hierarchy Chart
CListBox Class