Control zoom level of WinForms using mouse scroll wheel and Ctrl in VB.NET - vb.net

Question

If I have a winform, may I know how can I control the zoom level of the font in the application (as well as the application window itself obviously) by using Ctrl + Mouse Scroll Wheel? I see there is a Delta in the Scroll Wheel event, but not sure how that works. Is there any code sample that I can look into?

Answer 1

I suspect that you can just test:
(VB.NET):
If (ModifierKeys And Keys.Control) = Keys.Control Then
(C#):
if( (ModifierKeys & Keys.Control) == Keys.Control )
to check if the control key is down.

Answer 2

You'll have to handle the KeyDown and KeyUp event in order to determine whether or not Ctrl key is being held down. This value should be stored at class-level because it will be used by other subroutines besides the KeyDown and KeyUp events.
You then write code to handle the form's MouseWheel event. Scrolling downwards (towards you) causes a negative value for the Delta property of the MouseEventArgs. Scrolling upwards is obviously the reverse. The value of the Delta property is always currently 120.
Microsoft's reason for this value is as follows:
Currently, a value of 120 is the standard for one detent. If higher resolution mice are introduced, the definition of WHEEL_DELTA might become smaller. Most applications should check for a positive or negative value rather than an aggregate total.
In your context you'll just check for the sign of the Delta and perform an action.
Here is a sample code implementing basic 'zoom' functionality:
Public Class Form1
Enum ZoomDirection
None
Up
Down
End Enum
Dim CtrlIsDown As Boolean
Dim ZoomValue As Integer
Sub New()
' This call is required by the designer.
InitializeComponent()
' Add any initialization after the InitializeComponent() call.
ZoomValue = 100
End Sub
Private Sub Form1_KeyDown_KeyUp(ByVal sender As Object, _
ByVal e As KeyEventArgs) _
Handles Me.KeyDown, Me.KeyUp
CtrlIsDown = e.Control
End Sub
Private Sub Form1_MouseWheel(ByVal sender As Object,
ByVal e As MouseEventArgs) _
Handles Me.MouseWheel
'check if control is being held down
If CtrlIsDown Then
'evaluate the delta's sign and call the appropriate zoom command
Select Case Math.Sign(e.Delta)
Case Is < 0
Zoom(ZoomDirection.Down)
Case Is > 0
Zoom(ZoomDirection.Up)
Case Else
Zoom(ZoomDirection.None)
End Select
End If
End Sub
Private Sub Zoom(ByVal direction As ZoomDirection)
'change the zoom value based on the direction passed
Select Case direction
Case ZoomDirection.Up
ZoomValue += 1
Case ZoomDirection.Down
ZoomValue -= 1
Case Else
'do nothing
End Select
Me.Text = ZoomValue.ToString()
End Sub
End Class
Read on the following for more information about your question:
MSDN: Control.KeyDown Event
MSDN: Control.KeyUp Event
MSDN: Control.MouseWheel Event
MSDN: MouseEventArgs Class

Answer 3

For CrystalReportViewer1
Just put CrystalReportViewer1.Zoom(ZoomValue)
instead of the line Me.Text = ZoomValue.ToString() in the Sub Zoom