DriveListBox class

A DriveListBox is a Win32 native drop-down combo control that auto-populates with the drives reported by the operating system. The user picks one from the list; code reads the chosen drive through Drive and typically forwards it to a DirListBox (whose Path it can be assigned to directly) to build a file picker alongside a FileListBox. The control is normally placed on a Form or UserControl at design time. The default property is Drive and the default event is Change.

Private Sub Form_Load()
    Drive1.Drive = "C:"
    Dir1.Path = Drive1.Drive
    File1.Path = Dir1.Path
End Sub

Private Sub Drive1_Change()
    Dir1.Path = Drive1.Drive
End Sub

Drive list

The list is populated automatically when the underlying window is created, by asking the OS for every currently-attached drive. Each entry combines the drive letter with the volume label, or --- for a network drive --- the UNC path the drive is mapped to:

Entry shape	Meaning
c: [Windows]	Fixed or removable disk; volume label in brackets.
d: (no brackets)	Drive present but no volume label (unformatted, or empty CD-ROM).
z: [\\srv\share]	Network drive; UNC path in brackets.

Each entry is owner-drawn with an icon chosen from the drive type --- closed disk, removable, fixed, CD-ROM, network, or RAM disk. The list cannot be edited from code: AddItem, RemoveItem, and Clear are present in the type library for VB6 source compatibility but raise run-time error 438 (Object doesn't support this property or method) when called. Call Refresh to re-read the drive set from the OS --- useful after a removable medium is inserted or a network drive is mapped.

ListCount is the number of entries, List returns the text of any entry by zero-based index, and TopIndex controls vertical scrolling within the drop-down portion when it is open. NewIndex reports the position of the last entry added during population (useful only when re-reading the list from code).

Drive property semantics

Reading Drive returns the displayed text of the currently selected entry --- drive letter, colon, and (where applicable) the bracketed volume label or UNC path, exactly as shown in the combo.

Assigning to Drive looks only at the first character of the value and selects the entry whose drive letter matches (case-insensitively, by prefix). Anything after the first character is ignored, so "C", "C:", and "C:\Windows" all select the C: drive. If no entry matches the letter --- e.g. when the requested drive is not currently attached --- the assignment is silently ignored, leaving the previous selection in place. Assigning a value that matches the current selection does not raise Change; assigning a different value does.

Drive1.Drive = "D"          ' select drive D if present, else no-op
Debug.Print Drive1.Drive    ' "d: [Backup]"  (the displayed text)

OLE drag and drop

OLEDropMode lets the control act as a drop target (restricted to vbOLEDropNone or vbOLEDropManual). Source-side automatic OLE drag is not supported on this control --- VB6's OLEDragMode property was non-functional here and is omitted in twinBASIC. Call OLEDrag from code if a manual drag is needed.

Properties

Appearance

Determines how the control's border is drawn by the OS. A member of AppearanceConstants: vbAppearFlat or vbAppear3d (default).

BackColor

The background colour of the drop-down list entries, as an OLE_COLOR. Defaults to the system window-background colour. Selected entries paint with the system highlight colour regardless of this setting. Changing this calls Refresh so the new colour takes effect immediately.

CausesValidation

Determines whether the previously focused control's Validate event runs before this control receives the focus. Boolean, default True.

ControlType

A read-only ControlTypeConstants value identifying this control as a drive list box. Always vbDriveListBox.

DragIcon

A StdPicture used as the mouse cursor while the control is being drag-and-dropped (see Drag and DragMode).

DragMode

Whether the control should drag itself when the user holds the mouse over it. A member of DragModeConstants: vbManual (0, default --- call Drag from code) or vbAutomatic (1).

Drive

The currently selected drive. Default property.

Syntax: object.Drive [ = string ]

Reading returns the displayed text of the selected entry --- drive letter, colon, and (where applicable) the bracketed volume label or UNC path. Writing examines only the first character of string and selects the entry whose drive letter matches; values that do not match any present drive are silently ignored. Assigning a value that changes the selection raises Change. See Drive property semantics above for details.

Enabled

Determines whether the control accepts user input. A disabled drive list box still shows its current selection but is dimmed and ignores keyboard and mouse interaction. Boolean, default True.

Font

The StdFont used to render the drive entries. The convenience properties FontName, FontSize, FontBold, FontItalic, FontStrikethru, and FontUnderline read or write the corresponding members of this object.

ForeColor

The text colour for entries that are not currently selected, as an OLE_COLOR. Defaults to the system window-text colour. Disabled entries draw in the system grey-text colour, and selected entries draw in the system highlight-text colour, regardless of this setting. Changing this calls Refresh.

Height

The control's height when the drop-down is closed, in twips by default (or in the container's ScaleMode units). Single. The drop-down portion is sized by the OS.

HelpContextID

A Long identifying a topic in the application's help file, retrieved when the user presses F1 while the control has focus.

hWnd

The Win32 window handle for the underlying combo box, as a LongPtr. Read-only. Useful for passing to API functions.

Index

When the control is part of a control array, the Long zero-based index of this instance within the array. Read-only at run time.

Left

The horizontal distance from the left edge of the container to the left edge of the control. Single.

List

The displayed text of the drive entry at the given index. Read-only.

Syntax: object.List( Index )

Index

required A Long zero-based item position, from 0 to ListCount - 1.

ListCount

The number of drive entries currently in the list, as a Long. Read-only.

ListIndex

The zero-based index of the selected entry, or -1 if nothing is selected. Long. Assigning a value that differs from the current one selects that entry and raises Change.

MouseIcon

A StdPicture used as the mouse cursor when MousePointer is vbCustom and the pointer is over the control.

MousePointer

The mouse cursor shown when the pointer is over the control. A member of MousePointerConstants.

Name

The unique design-time name of the control on its parent form. Read-only at run time.

NewIndex

The zero-based index at which the most recent list-population step inserted an entry, or -1 if the list is empty. Long. Updated while the list is being filled (during Initialize and after Refresh); rarely useful at run time but read by some VB6-compatibility code.

OLEDropMode

How the control responds to OLE drops. A restricted member of OLEDropConstants: vbOLEDropNone or vbOLEDropManual. Automatic-drop mode is not supported on a DriveListBox.

Opacity

The control's opacity as a percentage (0--100, default 100). Values outside the range are clamped on Initialize. Requires Windows 8 or later for child controls.

Parent

A reference to the Form (or UserControl) that contains this control. Read-only.

TabIndex

The position of the control in the form's TAB-key navigation order. Long.

TabStop

Whether the user can reach the control by pressing the TAB key. Boolean, default True. A disabled control is skipped regardless of this setting.

Tag

A free-form String the application can use to associate custom data with the control. Ignored by the framework.

ToolTipText

A multi-line String displayed as a tooltip when the user hovers over the control.

Top

The vertical distance from the top of the container to the top of the control. Single.

TopIndex

The zero-based index of the entry shown at the top of the drop-down portion. Assigning a value scrolls the list so that entry is at the top, and raises Scroll when the value actually changes. Long.

TransparencyKey

An OLE_COLOR that, when set, becomes fully transparent in the rendered control. Default -1 disables the effect. Requires Windows 8 or later for child controls.

Visible

Whether the control is shown. Boolean, default True.

VisualStyles

Whether the OS theme engine should be used when drawing the control. Boolean.

WhatsThisHelpID

A Long identifying a "What's This?" help-pop-up topic in the application's help file. See ShowWhatsThis.

WheelScrollEvent

When True (default), mouse-wheel notifications over the drop-down list raise the Scroll event; when False, the wheel still scrolls the list but Scroll is suppressed. Boolean. VB6 never raised Scroll for wheel events; set this to False to match that behaviour exactly.

Width

The control's width. Single.

Methods

Drag

Begins, completes, or cancels a manual drag-and-drop operation when DragMode is vbManual. DriveListBox does not raise mouse events itself, so the call typically lives in a parent Form or container's mouse handler.

Syntax: object.Drag [ Action ]

Action

optional A member of DragConstants: vbCancel (0), vbBeginDrag (1, default), or vbEndDrag (2).

Move

Repositions and optionally resizes the control in a single call.

Syntax: object.Move Left [, Top [, Width [, Height ] ] ]

Left

required A Single giving the new horizontal position.

Top, Width, Height

optional New values for the corresponding properties. Omitted values are left unchanged.

OLEDrag

Initiates an OLE drag operation from the control, raising the OLEStartDrag event so the application can populate the DataObject.

Syntax: object.OLEDrag

Refresh

Re-reads the set of currently-attached drives from the operating system and repopulates the list, then redraws the control. Useful after a removable medium is inserted or a network drive is mapped or disconnected --- the control does not watch for these events on its own. Does not raise Change, even if the previously-selected drive is no longer present (the selection moves to entry 0).

Syntax: object.Refresh

SetFocus

Moves the input focus to the control. The control must be both Visible and Enabled, or run-time error 5 (Invalid procedure call or argument) is raised.

Syntax: object.SetFocus

ShowWhatsThis

Displays the topic identified by WhatsThisHelpID as a "What's This?" pop-up.

Syntax: object.ShowWhatsThis

ZOrder

Brings the control to the front or back of its sibling stack.

Syntax: object.ZOrder [ Position ]

Position

optional A member of ZOrderConstants: vbBringToFront (0, default) or vbSendToBack (1).

Events

Change

Raised after the selected drive changes --- whether the user picked a different entry from the drop-down or code assigned a different value to Drive or ListIndex. Not raised for assignments that match the current selection, nor during Refresh or the initial population that occurs before Initialize. Default event.

Syntax: object_Change( )

CloseUp

Raised when the drop-down portion closes --- either because the user picked an entry, clicked elsewhere, or pressed Esc.

Syntax: object_CloseUp( )

DragDrop

Raised on the destination control when a manual drag operation ends over it.

Syntax: object_DragDrop( Source As Control, X As Single, Y As Single )

DragOver

Raised on the control under the cursor while a manual drag operation is in progress.

Syntax: object_DragOver( Source As Control, X As Single, Y As Single, State As Integer )

DropDown

Raised when the user opens the drop-down portion.

Syntax: object_DropDown( )

GotFocus

Raised when the control receives the input focus.

Syntax: object_GotFocus( )

Initialize

Raised once, immediately after the underlying window is created and the initial list of drives has been loaded. New in twinBASIC --- VB6 had no equivalent on this control.

Syntax: object_Initialize( )

KeyDown

Raised when the user presses any key while the control has focus.

Syntax: object_KeyDown( KeyCode As Integer, Shift As Integer )

KeyPress

Raised when the user types a character that produces an ANSI keystroke.

Syntax: object_KeyPress( KeyAscii As Integer )

KeyUp

Raised when the user releases a key while the control has focus.

Syntax: object_KeyUp( KeyCode As Integer, Shift As Integer )

LostFocus

Raised when the control loses the input focus.

Syntax: object_LostFocus( )

OLECompleteDrag

Raised on the source control when the OLE drag operation finishes, indicating which effect (copy, move, none) the destination accepted.

Syntax: object_OLECompleteDrag( Effect As Long )

OLEDragDrop

Raised on the destination control when the user drops data on it.

Syntax: object_OLEDragDrop( Data As DataObject, Effect As Long, Button As Integer, Shift As Integer, X As Single, Y As Single )

OLEDragOver

Raised on the destination control while an OLE drag passes over it.

Syntax: object_OLEDragOver( Data As DataObject, Effect As Long, Button As Integer, Shift As Integer, X As Single, Y As Single, State As Integer )

OLEGiveFeedback

Raised on the source control during a drag so the application can adjust the cursor or other visual feedback.

Syntax: object_OLEGiveFeedback( Effect As Long, DefaultCursors As Boolean )

OLESetData

Raised on the source control when the destination requests data in a format that was registered but not yet supplied.

Syntax: object_OLESetData( Data As DataObject, DataFormat As Integer )

OLEStartDrag

Raised on the source control at the start of an OLE drag, so the application can populate the DataObject and choose the allowed effects.

Syntax: object_OLEStartDrag( Data As DataObject, AllowedEffects As Long )

Scroll

Raised when the drop-down list is scrolled --- by the scroll bar, the keyboard, or (when WheelScrollEvent is True) the mouse wheel. The new offset can be read from TopIndex.

Syntax: object_Scroll( )

Validate

Raised when the focus is moving to another control whose CausesValidation is True. Setting Cancel to True keeps the focus on this control.

Syntax: object_Validate( Cancel As Boolean )