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Are AutoScrolling bounds setup in World or Device coordinates

Platform: WinForms| Category: Drawing Tips
AutoScrollingMinSize is setup in device coordinates. If you are using a world coordinate
system other than pixels this means that you have to translate between world and device
coordinates before you set these value. You can use the Graphics.TransformPoints API to
do this as shown below.
g.TransformPoints(CoordinateSpace.Device, CoordinateSpace.World, ptScrollSize);
All this does is go from the GraphicsUnit that you are using to pixels. For example if your
GraphicsUnit is Inch, then with a Graphics object that represents a monitor screen you will
have translated values that come to about 100 pixels for every logical inch. Using this API
ensures that you are insulated from the underlying device. The values will be much higher
for printers.
Another important point to remember is that your Transform in the painting code (please
refer earlier FAQ in this section on AutoScrolling implementation) will have to be in
logical coordinates and will hence have to translate between logical and device coordinates.
protected void OnHandlePaint(object sender, PaintEventArgs args)
{
  Graphics g = args.Graphics;
  g.PageUnit = GraphicsUnit.Inch;

  // this will always be in pixels
  Point[] ptAutoScrollPos = new Point[]{this.AutoScrollPosition};
        
  // We have to convert the pixel value (device) to inches (logical..world)
  g.TransformPoints(CoordinateSpace.World, CoordinateSpace.Device, ptAutoScrollPos);
        
  // set up a simple translation so that we draw with respect to the doc bounds
  // and not the physical bounds
  g.TranslateTransform(ptAutoScrollPos[0].X, ptAutoScrollPos[0].Y); 

  g.DrawEllipse(_pen, _rectEllipse);
}
Play around with the sample and all should be clear. When you run the sample nothing will
be seen on the screen. Scroll around. Remember the logical units are in inches. You will
be looking at a huge ellipse!

Source: Syncfusion Staff

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