Customizing the OverviewControl to restricting to change the viewport as negative location
Restrict moving the viewport outside of the model
In Diagram’s overview control, we can restrict the movement of the viewport outside the model. This can be achieved by customizing the Diagram’s “OverviewControl” class. From the customized class, override the draw method and draw the “Viewport” logically based on the model area.
Here is the code example for restricting the viewport movement outside of the model.
[C#]
protected override void DrawViewport(Graphics grfx)
{
if (Diagram.View != null)
{
if ((ViewportBounds.X + ViewportBounds.Width > rcDisplayArea.X + rcDisplayArea.Width || ViewportBounds.X < rcDisplayArea.X)
|| (ViewportBounds.Y + ViewportBounds.Height > rcDisplayArea.Y + rcDisplayArea.Height || ViewportBounds.Y < rcDisplayArea.Y))
{
float heightDiff = 0;
float widthDiff = 0;
PointF pt = PointF.Empty;if (ViewportBounds.X + ViewportBounds.Width > rcDisplayArea.X + rcDisplayArea.Width)
{
// To prevent moving the viewport to the right
widthDiff = (ViewportBounds.X + ViewportBounds.Width) - (rcDisplayArea.X + rcDisplayArea.Width);
pt.X = ViewportBounds.X - widthDiff;
}
else
{
// To prevent moving the viewport to the top
if (ViewportBounds.X < rcDisplayArea.X)
{
widthDiff = rcDisplayArea.X - ViewportBounds.X;
}
pt.X = ViewportBounds.X + widthDiff;
}
if (ViewportBounds.Y + ViewportBounds.Height > rcDisplayArea.Y + rcDisplayArea.Height)
{
// To prevent moving the viewport to the bottom
heightDiff = (ViewportBounds.Y + ViewportBounds.Height) - (rcDisplayArea.Y + rcDisplayArea.Height);
pt.Y = ViewportBounds.Y - heightDiff;
}
else
{
// To prevent moving the viewport to the left
if (ViewportBounds.Y < rcDisplayArea.Y)
{
heightDiff = rcDisplayArea.Y - ViewportBounds.Y;
}
pt.Y = ViewportBounds.Y + heightDiff;
}
SizeF size = ViewportBounds.Size;
if (size.Width > rcDisplayArea.Width)
size.Width = rcDisplayArea.Width;
if (size.Height > rcDisplayArea.Height)
size.Height = rcDisplayArea.Height;ViewportBounds = new RectangleF(pt.X, pt.Y, size.Width, size.Height);
if (!(this.Diagram.Size.Width == 0 || this.Diagram.Size.Height == 0))
{
this.vpRenderer.DrawViewport(grfx, this.ForeColor);
}
}
else
{
base.DrawViewport(grfx);
}
}
}
[VB]
Protected Overrides Sub DrawViewport(ByVal grfx As Graphics) If Diagram.View IsNot Nothing Then If (ViewportBounds.X + ViewportBounds.Width > rcDisplayArea.X + rcDisplayArea.Width OrElse ViewportBounds.X < rcDisplayArea.X) OrElse (ViewportBounds.Y + ViewportBounds.Height > rcDisplayArea.Y + rcDisplayArea.Height OrElse ViewportBounds.Y < rcDisplayArea.Y) Then Dim heightDiff As Single = 0 Dim widthDiff As Single = 0 Dim pt As PointF = PointF.Empty If ViewportBounds.X + ViewportBounds.Width > rcDisplayArea.X + rcDisplayArea.Width Then 'to Prevent move the viewport in right widthDiff = (ViewportBounds.X + ViewportBounds.Width) - (rcDisplayArea.X + rcDisplayArea.Width) pt.X = ViewportBounds.X - widthDiff Else 'To prevent move the viewport in top If ViewportBounds.X < rcDisplayArea.X Then widthDiff = rcDisplayArea.X - ViewportBounds.X End If pt.X = ViewportBounds.X + widthDiff End If If ViewportBounds.Y + ViewportBounds.Height > rcDisplayArea.Y + rcDisplayArea.Height Then 'to prevent move the viewport in bottom heightDiff = (ViewportBounds.Y + ViewportBounds.Height) - (rcDisplayArea.Y + rcDisplayArea.Height) pt.Y = ViewportBounds.Y - heightDiff Else 'To prevent move the viewport in left If ViewportBounds.Y < rcDisplayArea.Y Then heightDiff = rcDisplayArea.Y - ViewportBounds.Y End If pt.Y = ViewportBounds.Y + heightDiff End If Dim size As SizeF = ViewportBounds.Size If size.Width > rcDisplayArea.Width Then size.Width = rcDisplayArea.Width End If If size.Height > rcDisplayArea.Height Then size.Height = rcDisplayArea.Height End If ViewportBounds = New RectangleF(pt.X, pt.Y, size.Width, size.Height) If Not(Me.Diagram.Size.Width = 0 OrElse Me.Diagram.Size.Height = 0) Then Me.vpRenderer.DrawViewport(grfx, Me.ForeColor) End If Else MyBase.DrawViewport(grfx) End If End If End Sub
Here is the sample for restricting to move the viewport as outside of the model.
Conclusion
I hope you enjoyed learning about customizing the OverviewControl to restrict the viewport from moving to a negative location.
You can refer to WinForms Diagram feature tour page to learn about its other groundbreaking feature representations and documentation, and how to quickly get started for configuration specifications. You can also explore our WinForms Diagram example to understand how to create and manipulate data.
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