DOCUMENT:Q177743 08-DEC-1997 [vbwin] TITLE :HOWTO: Scroll the TreeView When Dragging and Dropping a Node PRODUCT :Microsoft Visual Basic for Windows PROD/VER:WINDOWS:5.0 OPER/SYS:WINDOWS KEYWORDS:vb5all vb5howto VBKBAX VBKBComp VBKBCtrl ====================================================================== --------------------------------------------------------------------- The information in this article applies to: - Microsoft Visual Basic Professional and Enterprise Editions for Windows, version 5.0 --------------------------------------------------------------------- SUMMARY ======= The TreeView control supports drag-and-drop. When a Node is dragged to the top or bottom of the control, the control does not automatically scroll vertically. Because the control does not support scrolling when doing drag- and-drop, scrolling must be implemented by the developer. This article demonstrates one way to implement scrolling when performing drag-and-drop. MORE INFORMATION ================ The following example uses API calls to scroll the TreeView when the mouse pointer gets close to the bottom or top of the control and you are doing a drag-and-drop of a Node. Step-by-Step Example -------------------- 1. Create a new standard EXE project.Form1 is created by default. 2. Click Components on the Project menu. Check "Microsoft Windows Common Controls 5.0." 3. Add a Treeview, ImageList, and Timer to Form1. 4. Right-click the ImageList Control and select Properties from the pop-up menu. 5. On the General Tab of the Property Pages dialog, select 16 x 16. 6. Click the Images Tab, and insert 2 ICO files. NOTE: Icon files can be found in the directory ..\VB\Graphics\Icon. 7. Add the following code to the Code Window of Form1: Option Explicit Private Declare Function SendMessage Lib "user32" Alias _ "SendMessageA" (ByVal hwnd As Long, _ ByVal wMsg As Long, ByVal wParam As Long, lParam As Any) As Long Dim mfX As Single Dim mfY As Single Dim moNode As Node Dim m_iScrollDir As Integer 'Which way to scroll Dim mbFlag As Boolean Private Sub Form_DragOver(Source As Control, x As Single, y As _ Single, State As Integer) If Source.Name = "TreeView1" Then Timer1.Enabled = False End If End Sub Private Sub Form_Load() Dim i As Integer Dim n As Integer Timer1.Enabled = False Timer1.Interval = 200 TreeView1.Style = tvwTreelinesPlusMinusPictureText TreeView1.ImageList = ImageList1 'Populate TreeView controls For i = 1 To 50 TreeView1.Nodes.Add Text:="Node " & i, Image:=1, _ SelectedImage:=2 Next i For i = 1 To 50 For n = 1 To 5 TreeView1.Nodes.Add Relative:=i, Relationship:=tvwChild, _ Text:="Child Node " & n, _ Image:=1, SelectedImage:=2 Next n Next i End Sub Private Sub Timer1_Timer() Set TreeView1.DropHighlight = TreeView1.HitTest(mfX, mfY) If m_iScrollDir = -1 Then 'Scroll Up ' Send a WM_VSCROLL message 0 is up and 1 is down SendMessage TreeView1.hwnd, 277&, 0&, vbNull Else 'Scroll Down SendMessage TreeView1.hwnd, 277&, 1&, vbNull End If End Sub Private Sub TreeView1_DragDrop(Source As Control, x As Single, _ y As Single) ' If you were moving the Node you dragged to be the child ' of the Node you dropped it on, you would need to ' make moNode the selected Node after you made it a child If Not TreeView1.DropHighlight Is Nothing Then MsgBox moNode.Text & " was dropped on " & _ TreeView1.DropHighlight.Text End If Set TreeView1.DropHighlight = Nothing Set moNode = Nothing Timer1.Enabled = False End Sub Private Sub TreeView1_DragOver(Source As Control, x As Single, _ y As Single, State As Integer) Set TreeView1.DropHighlight = TreeView1.HitTest(x, y) mfX = x mfY = y If y > 0 And y < 100 Then 'scroll up m_iScrollDir = -1 Timer1.Enabled = True ElseIf y > (TreeView1.Height - 200) And y < TreeView1.Height Then 'scroll down m_iScrollDir = 1 Timer1.Enabled = True Else Timer1.Enabled = False End If End Sub Private Sub TreeView1_MouseUp(Button As Integer, Shift As Integer, _ x As Single, y As Single) Timer1.Enabled = False End Sub Private Sub TreeView1_MouseDown(Button As Integer, Shift As _ Integer, x As Single, y As Single) TreeView1.DropHighlight = TreeView1.HitTest(x, y) 'Make sure we are over a Node If Not TreeView1.DropHighlight Is Nothing Then TreeView1.SelectedItem = TreeView1.HitTest(x, y) Set moNode = TreeView1.SelectedItem ' Set the item being dragged. End If Set TreeView1.DropHighlight = Nothing End Sub Private Sub TreeView1_MouseMove(Button As Integer, Shift As _ Integer, x As Single, y As Single) If Button = vbLeftButton Then TreeView1.DragIcon = TreeView1.SelectedItem.CreateDragImage TreeView1.Drag vbBeginDrag End If End Sub 8. Save and run the sample. Select a Node and then drag it to the bottom of the TreeView. You will see the TreeView scroll. REFERENCES ========== For additional information, please see the following article in the Microsoft Knowledge Base: ARTICLE-ID: Q172272 TITLE : SAMPLE: Manipulating and Saving the Nodes in a TreeView Control For more information on the TreeView Control, please see the Visual Basic Online Help. Additional query words: dragdrop dragging dropping (c) Microsoft Corporation 1997, All Rights Reserved. Contributions by Brian Combs, Microsoft Corporation ====================================================================== Keywords : vb5all vb5howto VBKBAX VBKBComp VBKBCtrl Version : WINDOWS:5.0 Platform : WINDOWS Issue type : kbhowto ============================================================================= THE INFORMATION PROVIDED IN THE MICROSOFT KNOWLEDGE BASE IS PROVIDED "AS IS" WITHOUT WARRANTY OF ANY KIND. MICROSOFT DISCLAIMS ALL WARRANTIES, EITHER EXPRESS OR IMPLIED, INCLUDING THE WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE. IN NO EVENT SHALL MICROSOFT CORPORATION OR ITS SUPPLIERS BE LIABLE FOR ANY DAMAGES WHATSOEVER INCLUDING DIRECT, INDIRECT, INCIDENTAL, CONSEQUENTIAL, LOSS OF BUSINESS PROFITS OR SPECIAL DAMAGES, EVEN IF MICROSOFT CORPORATION OR ITS SUPPLIERS HAVE BEEN ADVISED OF THE POSSIBILITY OF SUCH DAMAGES. SOME STATES DO NOT ALLOW THE EXCLUSION OR LIMITATION OF LIABILITY FOR CONSEQUENTIAL OR INCIDENTAL DAMAGES SO THE FOREGOING LIMITATION MAY NOT APPLY. Copyright Microsoft Corporation 1997.