private void EnterReaderMode()
{
_pbGlyph.Location = Point.Subtract(PointToClient(MousePosition), new Size(_pbGlyph.Width / 2, _pbGlyph.Height / 2));
SetCursor(new HandleRef(Cursors.NoMoveVert, Cursors.NoMoveVert.Handle));
_autoScrollTimer.Start();
_endOnMouseUp = false;
// bounds to get the scrolling sensitivity
var scrollBounds = new Rectangle(_pbGlyph.Left, _pbGlyph.Top, _pbGlyph.Right, _pbGlyph.Bottom);
IntPtr rectPtr = Marshal.AllocHGlobal(Marshal.SizeOf(scrollBounds));
try
{
Marshal.StructureToPtr(scrollBounds, rectPtr, true);
var readerInfo = new READERMODEINFO
{
hwnd = Handle,
fFlags = ReaderModeFlags.VerticalOnly,
prc = rectPtr,
lParam = IntPtr.Zero,
fFlags2 = TranslateDispatchCallback,
pfnScroll = ReaderScrollCallback
};
readerInfo.cbSize = Marshal.SizeOf(readerInfo);
DoReaderMode(ref readerInfo);
}
finally
{
Marshal.FreeHGlobal(rectPtr);
}
}
private bool ReaderScrollCallback(ref READERMODEINFO prmi, int dx, int dy)
{
if (dy == 0)
{
_scrollIncrementY = 0;
}
else
{
// Could be placebo, but using actual cursor delta rather than dy (which is a much smaller value)
// seems to allow for a smoother acceleration curve (I feel like I notice some minor chunkiness
// if I use dy)
int cursY = Cursor.Position.Y;
int origY = PointToScreen(_pbGlyph.Location).Y + (_pbGlyph.Height / 2);
int delta = cursY < origY ? origY - cursY : cursY - origY;
// Exponential scroll like most apps do - somewhat arbitrary values but has a decent feel.
// Clamp to 1 (pixel) to correct for loss of precision in divide where it could end up as 0 for
// too long.
// OCD
int deltaSquared;
try
{
deltaSquared = checked (delta * delta);
}
catch (OverflowException)
{
deltaSquared = int.MaxValue;
}
int increment = (deltaSquared / 640).Clamp(1, 1024);
_scrollIncrementY = cursY < origY ? -increment : increment;
_endOnMouseUp = true;
}
return(true);
}
static extern void DoReaderMode(ref READERMODEINFO prmi);
private bool ReaderScrollCallback(ref READERMODEINFO prmi, int dx, int dy)
{
// TODO: Scroll around within your control here
return false;
}
private void EnterReaderMode()
{
READERMODEINFO readerInfo = new READERMODEINFO
{
hwnd = this.textBox1.Handle,
fFlags = 0,
prc = IntPtr.Zero,
lParam = IntPtr.Zero,
fFlags2 = new TranslateDispatchCallbackDelegate(this.TranslateDispatchCallback),
pfnScroll = new ReaderScrollCallbackDelegate(this.ReaderScrollCallback)
};
readerInfo.cbSize = Marshal.SizeOf(readerInfo);
DoReaderMode(ref readerInfo);
}
internal static extern void DoReaderMode(ref READERMODEINFO prmi);