Question

I have a panel with autoscroll and I need to change the mouse scroll lines number

I will mean this:

(Mouse properties in spanish, sorry)

But I will change it in my program, for my panel, obvius, not in the SO!

PS: for example the Winamp media player have an option for that.

I can’t find info anywhere, please help.

UPDATE

My scrollbar is a panel with “AutoScroll” property

My event is this:

    Private Sub Panel1_MouseScroll(sender As Object, e As MouseEventArgs) Handles Panel1.MouseWheel

    Panel1.Invalidate()

    End Sub

This is the content of my panel:

  ' Checkbox drawing
Public Sub updatecheckboxes()
    ' delete the old checkboxes
    Panel1.Controls.Clear()
    ' create the new checkboxes
    Dim filesystem = CreateObject("Scripting.FileSystemObject")
    Dim ThisDir = filesystem.GetFolder(My.Settings.folderpath)
    Dim i As Int32 = 0
    Dim pos As Int32 = 10
    For Each folder In ThisDir.Subfolders
        Array.Resize(mcheck, i + 1)
        mcheck(i) = New CheckBox
        With mcheck(i)
            .AutoSize = True
            .Location = New Point(10, pos)
            .Name = "CheckBox" & i + 1
            .Text = folder.Name
        End With
        Me.Panel1.Controls.Add(mcheck(i))
        AddHandler mcheck(i).CheckedChanged, AddressOf LlamadaCheckBox
        i += 1
        pos += 20
    Next

End Sub

I want to change the number of scrolled lines because of the distorted efefct inside the panel, If i use “one scoll-page” or “10 scrolls at time” like the imagen of Windows SO properties then I can fix it!

Answer 1

You can use SendMessage to scroll by any number of lines you want, regardless of what’s in SystemInformation.MouseWheelScrollLines. MouseWheel event does not occur for a Panel. So I tested this on a TextBox:

Private Declare Function SendMessage Lib "user32" Alias "SendMessageA" _
               (ByVal handle As IntPtr, ByVal wMsg As Integer,
                ByVal wParam As Integer, ByVal lParam As Integer) As Integer

Scroll one line up:

SendMessage(TextBox1.Handle, &HB6, 0, -1)

Scroll one line down:

SendMessage(TextBox1.Handle, &HB6, 0, 1)

The last parameter is a number of lines, sign indicates direction. Negative – up, positive – down.

You should be able to override/suppress mouse wheel handling and insert these two statements instead, depending on the sign of delta value being passed.