How to zoom to the cursor position after the graphics component has been transformed?
I want to be able to zoom to any of the test rectangles.
The panning is done with the Middle mouse button.
MouseWheel Event handles the zooming.
Ignore the DrawGrid method, it's just to get some visual reference.
Public Class Diagram
Dim renderOrigin As New Point
Dim zoom As Single = 1.0F
Dim startPoint As New Point
Dim isDragging As Boolean = False
Dim gridSpacing As Integer = 50
Dim testRects() As Rectangle = New Rectangle() {New Rectangle(-150, -150, 70, 25), _
New Rectangle(-10, -5, 70, 25), _
New Rectangle(100, 8, 70, 25), _
New Rectangle(300, 80, 70, 25)}
Sub New()
SetStyle(ControlStyles.ResizeRedraw, True)
SetStyle(ControlStyles.OptimizedDoubleBuffer, True)
SetStyle(ControlStyles.AllPaintingInWmPaint, True)
' This call is required by the designer.
InitializeComponent()
' Add any initialization after the InitializeComponent() call.
End Sub
Protected Overrides Sub OnPaint(e As PaintEventArgs)
Dim g As Graphics = e.Graphics
g.TranslateTransform(renderOrigin.X, renderOrigin.Y)
g.ScaleTransform(zoom, zoom)
drawGrid(g)
g.FillRectangles(Brushes.Green, testRects.ToArray)
End Sub
Private Sub drawGrid(ByRef g As Graphics)
If zoom < 0.6 Then
Exit Sub
End If
Dim oX As Integer = renderOrigin.X
Dim oY As Integer = renderOrigin.Y
Dim maxStepX As Integer = Math.Ceiling((Width - oX) / gridSpacing) / zoom
Dim maxStepY As Integer = Math.Ceiling((Height - oY) / gridSpacing) / zoom
Dim minStepX As Integer = Math.Floor((oX * -1) / gridSpacing) / zoom
Dim minStepY As Integer = Math.Floor((oY * -1) / gridSpacing) / zoom
For x = minStepX To maxStepX
For y = minStepY To maxStepY
g.DrawLine(Pens.Black, x * gridSpacing, gridSpacing * y, (x + 1) * gridSpacing, gridSpacing * y)
g.DrawLine(Pens.Black, x * gridSpacing, gridSpacing * y, x * gridSpacing, (y + 1) * gridSpacing)
Next
Next
End Sub
Private Sub Diagram_MouseDown(sender As Object, e As MouseEventArgs) Handles Me.MouseDown
If e.Button = Windows.Forms.MouseButtons.Middle Then
startPoint = New Point(e.X - renderOrigin.X, e.Y - renderOrigin.Y)
isDragging = True
End If
End Sub
Private Sub Diagram_MouseMove(sender As Object, e As MouseEventArgs) Handles Me.MouseMove
If isDragging Then
renderOrigin = New Point(e.X - startPoint.X, e.Y - startPoint.Y)
Invalidate()
End If
End Sub
Private Sub Diagram_MouseUp(sender As Object, e As MouseEventArgs) Handles Me.MouseUp
isDragging = False
End Sub
Private Sub Diagram_MouseWheel(sender As Object, e As MouseEventArgs) Handles Me.MouseWheel
Dim i As Single = (e.Delta / Math.Abs(e.Delta)) / 100
zoom += i
If zoom < 0.1 Then zoom = 0.1
If zoom > 1.0 Then zoom = 1.0
renderOrigin = New Point(e.X - e.X * zoom, e.Y - e.Y * zoom)
Invalidate()
End Sub
End Class
