public void DeviceToUser(ref double x, ref double y)
{
Cairo.Matrix inv = (Cairo.Matrix) this.transformMatrix.Clone();
Cairo.Status cs = inv.Invert();
if (cs == Cairo.Status.Success)
{
inv.TransformPoint(ref x, ref y);
}
else
{
throw new Exception("Unable to transform device coordinates to user coordinates because the matrix was uninvertible (" + cs.ToString() + ").");
}
}
//
// this functions calculates the transformation needed to center and completely fill the
// viewport with the Surface at the given tilt
//
public Matrix Fill(Gdk.Rectangle viewport, double tilt)
{
if (tilt == 0.0)
return Fill (viewport);
Matrix m = new Matrix ();
m.InitIdentity ();
double len;
double orig_len;
if (Bounds.Width > Bounds.Height) {
len = viewport.Height;
orig_len = Bounds.Height;
} else {
len = viewport.Width;
orig_len = Bounds.Width;
}
double a = Math.Sqrt (viewport.Width * viewport.Width + viewport.Height * viewport.Height);
double alpha = Math.Acos (len / a);
double theta = alpha - Math.Abs (tilt);
double slen = a * Math.Cos (theta);
double scale = slen / orig_len;
double x_offset = (viewport.Width - Bounds.Width * scale) / 2.0;
double y_offset = (viewport.Height - Bounds.Height * scale) / 2.0;
m.Translate (x_offset, y_offset);
m.Scale (scale, scale);
m.Invert ();
m.Translate (viewport.Width * 0.5, viewport.Height * 0.5);
m.Rotate (tilt);
m.Translate (viewport.Width * -0.5, viewport.Height * -0.5);
m.Invert ();
return m;
}