/// <summary>
/// Get the scroll position of a text box.
/// </summary>
public static unsafe Win32.POINT GetScrollPos(IntPtr handle)
{
Win32.POINT res = new Win32.POINT();
IntPtr ptr = new IntPtr(&res);
Win32.SendMessage(handle, Win32.EM_GETSCROLLPOS, 0, ptr);
return(res);
}
/// <summary>
/// Helper function for dealing with strange Windows behavior.
/// When a text box is bigger than 65535 pixels, Windows applies some strange
/// scaling to whatever value you pass in to SetScrollPos(). The same scaling
/// is not applied to GetScrollPos(), meaning that if you set the scroll pos
/// to the value you just received from GetScrollPos(), the position will
/// actually jump.
///
/// This function compensates for that by finding a value to send to SetScrollPos
/// so that GetScrollPos() returns the value specified by point.
/// </summary>
public static void SetScrollPos(IntPtr handle, Win32.POINT point)
{
double t0 = -1, t1 = 0, y0 = -1, y1 = 0;
int iter_max = 100;
while (iter_max-- > 0)
{
double t = (point.y - y0) / (y1 - y0) * (t1 - t0) + t0;
SetScrollPosRaw(handle, new Win32.POINT(point.x, (int)t));
Win32.POINT p = GetScrollPos(handle);
double yres = p.y;
if ((int)yres == point.y || (int)yres == y1 || (int)t == t1)
{
break;
}
t0 = t1;
y0 = y1;
t1 = t;
y1 = yres;
}
}
/// <summary>
/// Set the scroll position of a text box.
/// </summary>
public static unsafe void SetScrollPosRaw(IntPtr handle, Win32.POINT point)
{
IntPtr ptr = new IntPtr(&point);
Win32.SendMessage(handle, Win32.EM_SETSCROLLPOS, 0, ptr);
}
