RichTextBox Tricks and Tips

[moeur]

The RichTextBox control has the ability to detect URLs as they are typed. It can convert this text into a hyperlink which can launch a browser when clicked.

To turn on Auto URL detection simply send the RTB an EM_AUTOURLDETECT message.

When the control detects that a URL is being entered, it reformats the text being entered so that it looks like a hyperlink and marks that text with a CFE_LINK effect.

When the mouse pointer is over text with a CFE_LINK effect, the RTB can be configured to send a message to its parent. In order to respond to mouse events over the hyperlink text, the parent has to be subclassed or hooked.

The following code shows how to setup Auto URL detection

Public Sub EnableAutoURLDetection(RTB As RichTextBox)

    'enable auto URL detection
    SendMessage RTB.hwnd, EM_AUTOURLDETECT, 1&, ByVal 0&

    'subclass the parent of the RTB to receive EN_LINK notifications
    Set FormSubClass = New clsSubClass
    FormSubClass.Enable RTB.Parent.hwnd
    
    'set RTB to notify parent when user has clicked hyperlink
    SendMessage RTB.hwnd, EM_SETEVENTMASK, 0&, ByVal ENM_LINK

End Sub

And to respond to a left mouse click you could do the following in your form's subclass routine.

Private Sub FormSubClass_WMArrival(hwnd As Long, uMsg As Long, wParam As Long, lParam As Long, lRetVal As Long)
Dim notifyCode As nmhdr
Dim LinkData As ENLINK
Dim URL As String

    Select Case uMsg
    Case WM_NOTIFY

        CopyMemory notifyCode, ByVal lParam, LenB(notifyCode)
        If notifyCode.code = EN_LINK Then
        'A RTB sends EN_LINK notifications when it receives certain mouse messages
        'while the mouse pointer is over text that has the CFE_LINK effect:
        
        'To receive EN_LINK notifications, specify the ENM_LINK flag in the mask
        'sent with the EM_SETEVENTMASK message.
        
        'If you send the EM_AUTOURLDETECT message to enable automatic URL detection,
        'the RTB automatically sets the CFE_LINK effect for modified text that it
        'identifies as a URL.
        
            CopyMemory LinkData, ByVal lParam, Len(LinkData)
            If LinkData.Msg = WM_LBUTTONUP Then
                'user clicked on a hyperlink
                'get text with CFE_LINK effect that caused message to be sent
                URL = Mid(RTB.Text, LinkData.chrg.cpMin + 1, LinkData.chrg.cpMax - LinkData.chrg.cpMin)
                'launch the browser here
                ShellExecute 0&, "OPEN", URL, vbNullString, "C:\", SW_SHOWNORMAL
            End If

        End If
        lRetVal = FormSubClass.callWindProc(hwnd, uMsg, wParam, lParam)
        
    Case Else
        lRetVal = FormSubClass.callWindProc(hwnd, uMsg, wParam, lParam)
    End Select

End Sub

Attached is a project that demonstrates the whole idea.