QRCode class

A QRCode is a windowless lightweight control that renders a QR code generated from its Payload — a URL, plain text, or a raw byte array. The encoding is performed in-process by the embedded qrcodegen library and the resulting matrix is painted directly on the parent at design time and at run time. The picture is regenerated automatically whenever any of the encoding properties changes, so a QR control can be wired up declaratively to data bindings or to other UI state with no plumbing.

Like Image, a QRCode has no hWnd and is not focusable. It is the right choice for embedding a scannable code in a form (login, payment, Wi-Fi credentials, contact card, app deep link, etc.) without paying for a heavy PictureBox.

The default property is Picture (the read-only generated image) and the default event is Click.

Private Sub Form_Load()
    QRCode1.Payload = "https://www.twinbasic.com"
    QRCode1.EccMode = vbQRCodegenEccHigh    ' 30 % parity
    QRCode1.ForeColor = vbBlue
End Sub

Private Sub QRCode1_Click()
    MsgBox "QR code clicked"
End Sub

• Windowless rendering
• Encoding the payload
• Error correction
• Version and mask
• Module rendering
• Border
• OLE drag-drop
• Data binding
• Properties
• Methods
• Events

Windowless rendering

A QRCode has no hWnd. The framework paints it directly onto its parent’s drawing surface during the parent’s paint cycle. The trade-offs are the same as for any windowless control:

• No focus, no keyboard input, no KeyDown / KeyPress / KeyUp / GotFocus / LostFocus / Validate.
• No hWnd to pass to API functions, and no SetFocus.
• Cannot host child controls.

For a QR code that needs any of those, host the QRCode inside a PictureBox or Frame and put the focusable controls next to it.

Encoding the payload

The Payload property is a Variant that accepts either a String (text or URL) or a one-dimensional Byte() array (for binary data). The encoder picks the most compact segment mode automatically — numeric, alphanumeric, or byte — based on the contents of the string; for a byte array the byte mode is used unconditionally and the data is encoded verbatim. Empty payloads clear Picture to Nothing; at design time the rectangle then shows a (no payload text) placeholder.

The QR code is regenerated whenever Payload, ForeColor, ModuleSize, SquareModules, EccMode, EccBoost, MinVersion, MaxVersion, or MaskType changes, and the new picture becomes visible through Picture. Refresh only repaints — it does not force re-encoding.

Error correction

QR codes embed a Reed-Solomon parity stream that lets the decoder recover from damage to a portion of the matrix. EccMode chooses how much of the matrix is dedicated to parity:

Constant	Value	Approx. recovery
vbQRCodegenEccLow	0	7%
vbQRCodegenEccMedium	1	15%
vbQRCodegenEccQuartile	2	25%
vbQRCodegenEccHigh	3	30%

When EccBoost is True (default), the encoder raises the parity level beyond the configured minimum if doing so still fits the payload in the same QR version — getting better resilience for free.

Version and mask

The QR-code version (1 to 40) sets the matrix size: version 1 is 21 × 21 modules, version 40 is 177 × 177. MinVersion and MaxVersion constrain the encoder’s search; it picks the smallest version in the range that fits the payload at the chosen EccMode. The defaults (1 and 40) span the full range. Values outside 1..40 are clamped, and if MinVersion ends up greater than MaxVersion it is reset to 1.

MaskType selects one of eight masks applied to the matrix to break up patterns that confuse the scanner. vbQRCodegenMaskAuto (-1, default) picks the mask with the best penalty score; the eight named values vbQRCodegenMask0 through vbQRCodegenMask7 force a specific one — useful for reproducibility.

Module rendering

ModuleSize is the pixel size of one module of the generated Picture. Default 120. The picture is rescaled down to the control’s rectangle at paint time, so the choice of ModuleSize only matters when the picture is being saved or pulled out for use elsewhere (clipboard, drag-drop, SavePicture, …).

SquareModules chooses how each module is drawn in the picture: as a filled square (True, default) or as a filled circle (False — a stylistic choice that most scanners still tolerate).

Square, in contrast, controls the rendering of the picture on the control: with True (default) the picture is letter-boxed and centred so it stays square regardless of the control’s aspect ratio; with False the picture is stretched to fill the rectangle.

Border

BorderStyle chooses between no border (default) and a single sunken border drawn around the rectangle. When a border is present, Appearance selects between a 3-D and a flat (monochrome) version of it.

OLE drag-drop

A QRCode supports both ends of an OLE drag-drop operation:

• OLEDragMode controls the source side. With vbOLEDragAutomatic, holding the mouse over the control and beginning a drag automatically picks up the current Picture into the resulting DataObject — handy for dragging the generated QR onto another picture display or out to a file in Explorer. With vbOLEDragManual (default) drags must be initiated by calling OLEDrag from a MouseDown handler.
• OLEDropMode controls the destination side. With vbOLEDropManual the OLEDragOver and OLEDragDrop events fire so the application can decide what to do — for example, set Payload to the dropped text. vbOLEDropAutomatic is not supported on a QRCode and assigning it raises run-time error 5 (Invalid procedure call or argument).

Data binding

Setting DataSource and DataField connects the control to a field of a Data control’s recordset. Binding is asymmetric:

• Inbound (recordset → control): non-null, non-empty field values are interpreted as text and assigned to Payload; the QR is then re-encoded and repainted. Null and empty values clear Picture to Nothing.
• Outbound (control → recordset): the current QR Picture is serialised as a byte array and written back to the bound field — useful for storing a snapshot of the rendered code, but note that what comes out of the binding is not the same as what went in.

Properties

Anchors

The set of edges of the parent that the control’s corresponding edges follow when the parent resizes. Read-only — assign individual .Left, .Top, .Right, .Bottom flags through the returned Anchors object.

Appearance

The style of the border, as a member of AppearanceConstants: vbAppearFlat or vbAppear3d (default). Only meaningful when BorderStyle is vbFixedSingleBorder.

BorderStyle

The style of border drawn around the rectangle. A member of ControlBorderStyleConstants: vbNoBorder (0, default) or vbFixedSingleBorder (1).

Container

The control that hosts this QRCode — typically the form, a Frame, a PictureBox, or a UserControl. Read with Get, change with Set.

ControlType

A read-only ControlTypeConstants value identifying the underlying control kind. Always vbImage — the QRCode shares its control-type tag with Image.

DataChanged

Whether the bound Picture has been written to since the last save or refresh from the DataSource. Boolean. Setting DataChanged = True also marks the bound recordset as dirty.

DataField

The name of the field, in the recordset of the bound DataSource, whose value drives Payload. String.

DataFormat

A StdDataFormat that converts between the raw recordset value and the displayed payload, when the application needs custom handling. Set with Set.

DataMember

When the DataSource exposes more than one recordset, the name of the member to bind to. String.

DataSource

A reference to a Data control (or other DataSource provider) whose recordset supplies the value for DataField. Set with Set.

Dock

Where the control is docked within its container. A member of DockModeConstants: vbDockNone (default), vbDockLeft, vbDockTop, vbDockRight, vbDockBottom, or vbDockFill. Docked controls ignore Anchors.

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 (the manual VB-drag form, distinct from OLE drag) when the user holds the mouse over it. A member of DragModeConstants: vbManual (0, default — call Drag from code) or vbAutomatic (1).

EccBoost

When True (default), the encoder is allowed to raise the actual parity level above EccMode when the payload still fits the same QR version at the higher level. Boolean. Set to False for reproducible output across payloads of varying length.

EccMode

The minimum error-correction level used when encoding. A member of QRCodegenEccConstants (defined in the VB package):

Constant	Value	Approx. recovery
vbQRCodegenEccLow	0	7%
vbQRCodegenEccMedium	1	15%
vbQRCodegenEccQuartile	2	25%
vbQRCodegenEccHigh	3	30%

Default vbQRCodegenEccLow. Out-of-range values are clamped.

Enabled

Determines whether the control accepts mouse input. A disabled QRCode still paints normally but does not raise mouse events. Boolean, default True.

ForeColor

The colour of the dark modules in the generated QR code, as an OLE_COLOR. Default vbBlack. The light modules are always transparent — the control’s parent shows through them, so place the QRCode over a contrasting background.

Height

The control’s height, in twips by default (or in the container’s ScaleMode units). Double.

Index

When the control is part of a control array, the Long zero-based index of this instance within the array. Reading Index on a non-array instance raises run-time error 343 (Object not an array). Read-only at run time.

Left

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

MaskType

The mask applied to the encoded matrix to break up patterns that confuse the scanner. A member of QRCodegenMaskConstants (defined in the VB package): vbQRCodegenMaskAuto (-1, default — pick the mask with the lowest penalty score) or one of vbQRCodegenMask0 … vbQRCodegenMask7 (force the corresponding numbered mask). Out-of-range values fall back to vbQRCodegenMaskAuto.

MaxVersion

The largest QR version the encoder is allowed to choose. Long, default 40. Clamped to 1..40. If MinVersion exceeds MaxVersion at encode time, MinVersion is reset to 1.

MinVersion

The smallest QR version the encoder is allowed to choose. Long, default 1. The encoder picks the smallest version in MinVersion..MaxVersion that fits the payload at the requested EccMode. Clamped to 1..40.

ModuleSize

The pixel size of one QR module in the generated Picture. Long, default 120. The picture is scaled to the control’s rectangle at paint time, so a larger ModuleSize only matters when the picture is being captured or saved at its native resolution.

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.

OLEDragMode

Whether an OLE drag is started automatically when the user begins dragging the control. A member of OLEDragConstants: vbOLEDragManual (0, default — application calls OLEDrag) or vbOLEDragAutomatic (1 — the framework picks up the current Picture into the resulting DataObject automatically).

OLEDropMode

How the control responds to OLE drops landing on it. A restricted member of OLEDropConstants: vbOLEDropNone (0, default) or vbOLEDropManual (1). Automatic drop is not supported on a QRCode; assigning vbOLEDropAutomatic raises run-time error 5 (Invalid procedure call or argument).

Parent

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

Payload

The data encoded in the QR code. Variant, default "https://www.twinbasic.com".

Syntax: object.Payload [ = value ]

Accepts a String for text or URL payloads, or a one-dimensional Byte() array for arbitrary binary data. The encoder picks the most compact segment mode automatically — numeric, alphanumeric, or byte — based on the contents of the string. Assigning an empty value clears Picture to Nothing.

Picture

The generated QR code, as a StdPicture. Default property. Read-only — produced by the encoder from Payload and the other encoding properties. Returns Nothing when Payload is empty.

Square

Whether the generated picture is rendered with a 1:1 aspect ratio inside the control’s rectangle (True, default — picture is centred and letter-boxed) or stretched to fill it (False). Boolean.

SquareModules

Whether each module of the encoded matrix is drawn in the picture as a filled square (True, default) or as a filled circle (False). Boolean.

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. Double.

Visible

Whether the control is shown. Boolean, default True. Hidden QRCodes skip the paint pass entirely at run time, except in the IDE designer where they always render so the developer can position them.

WhatsThisHelpID

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

Width

The control’s width, in twips by default (or in the container’s ScaleMode units). Double.

Methods

Drag

Begins, completes, or cancels a manual VB-style drag operation. Distinct from OLE drag — see OLEDrag.

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 (or, if the source has already been pre-populated, kicks off the drag immediately).

Syntax: object.OLEDrag

Refresh

Forces an immediate repaint of the control’s rectangle on the parent’s drawing surface. Does not re-encode the QR — for that, reassign Payload (or any of the encoding properties) which triggers regeneration automatically.

Syntax: object.Refresh

ShowWhatsThis

Displays the topic identified by WhatsThisHelpID as a “What’s This?” pop-up.

Syntax: object.ShowWhatsThis

ZOrder

Brings the QRCode to the front or back of the windowless-sibling stack within its container.

Syntax: object.ZOrder [ Position ]

Position

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

Events

Click

Raised when the user single-clicks the control’s rectangle. Default event.

Syntax: object_Click( )

DblClick

Raised when the user double-clicks the control’s rectangle.

Syntax: object_DblClick( )

DragDrop

Raised on the destination control when a manual VB-style 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 VB-style drag operation is in progress.

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

Initialize

Raised once, after the control has been wired into its container’s paint cycle but before it is first painted. Useful for last-minute setup that depends on container state.

Syntax: object_Initialize( )

MouseDown

Raised when the user presses any mouse button over the control.

Syntax: object_MouseDown( Button As Integer, Shift As Integer, X As Single, Y As Single )

MouseMove

Raised when the cursor moves over the control.

Syntax: object_MouseMove( Button As Integer, Shift As Integer, X As Single, Y As Single )

MouseUp

Raised when the user releases a mouse button over the control.

Syntax: object_MouseUp( Button As Integer, Shift As Integer, X As Single, Y As Single )

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. Also raised automatically when OLEDragMode is vbOLEDragAutomatic and the user begins a drag.

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