How to lock cursor to game window?

Question

I'm trying to implement camera movement for an FPS game. I think I've almost got it, but there's just a few more kinks to work out. I've got my mouse movement set up like this:

protected override void OnLoad(EventArgs e)
{
    Mouse.Move += OnMouseMove;
}

void OnMouseMove(object sender, MouseMoveEventArgs e)
{
    _lookDir.X += e.XDelta * _mouseSensitivity;
    _lookDir.Y -= e.YDelta * _mouseSensitivity;
}

Which seems to work pretty well when the mouse is actually inside the window, but as soon as I leave the window it doesn't work. I think what I have to do is somehow constrain the mouse to be inside the window, because even if it triggered a mouse move when my mouse was outside of the window, and still run into the same issue, just at the bounds on my desktop coords instead.

So...how do I do that -- lock my mouse to inside the window? Do I essentially just keep setting the mouse position to the center? If so...how do I set the mouse position? I'm using Windows, but I'd prefer a non-native solution if OpenTK provides it.

SDL offers [a proper solution](http://gamedev.stackexchange.com/a/33554/800) to this problem. I'm writing [a wrapper](https://bitbucket.org/mnbayazit/glow) for it, but it will be awhile before it's ready (if ever). — mpen, Aug 13 '13 at 17:44

score 3 · Accepted Answer · answered Jul 30 '20 at 14:40

3

Quite simple in OpenTK 3.2

OpenTK.GameWindow window = new OpenTK.GameWindow();
window.CursorGrabbed = true;

You can additionally use this snippet to hide the cursor. Just implement it as needed.

window.Cursor = MouseCursor.Empty;

answered Jul 30 '20 at 14:40

Wilke Schröder

46
1

score 2 · Answer 2 · answered Feb 12 '12 at 00:55

2

One practice that I have done, and that the old Quake games used (and half-life 1), is every frame you reset the cursor position to be the middle of the screen, then you calculate the delta from the middle of the screen.

EDIT: And to move the cursor, check out Cursor.Position

answered Feb 12 '12 at 00:55

Matthew

24,703
9
76
110

System.Windows.Forms == Windows-specific != Non-native. I guess I'll have to use that for now though. Thanks. – mpen Feb 12 '12 at 00:59
1

Sorry, I'm not familiar with OpenTK, for .net you can use Cursor.Position, or for win32 you can use Set/GetCursorPos. For linux / mac I have no idea of a cross platform way of accomplishing this. – Matthew Feb 12 '12 at 01:01

score 1 · Answer 3 · answered Feb 12 '12 at 19:50

This is my solution right now...it's specific to windows though.

protected void ResetCursorPosition()
{
    Cursor.Position = WindowCenter;
    _lastMousePos = Cursor.Position;
}

protected void LockMouse()
{
    _lockMouse = true;
    _origCursorPosition = Cursor.Position;
    CursorVisible = false;
    ResetCursorPosition();
}

protected void UnlockMouse()
{
    _lockMouse = false;
    CursorVisible = true;
    Cursor.Position = _origCursorPosition;
}

void OnMouseDown(object sender, MouseButtonEventArgs e)
{
    if (!_lockMouse) LockMouse();
}

void OnKeyDown(object sender, KeyboardKeyEventArgs e)
{
    if(e.Key == Key.Escape)
    {
        if (_lockMouse) UnlockMouse();
        else Exit();
    }
}

protected override void OnUpdateFrame(FrameEventArgs e)
{
    Title = string.Format("{0} - {1:0.0} FPS", _windowTitle, RenderFrequency);

    float moveSpeed = Keyboard[RunKey] ? 0.9f : 0.4f;

    if (Keyboard[MoveForwardKey])
    {
        _pos.X += (float)Math.Cos(_lookDir.X) * moveSpeed;
        _pos.Z += (float)Math.Sin(_lookDir.X) * moveSpeed;
    }

    if (Keyboard[StrafeLeftKey]) // FIXME: holding W + A gives extra speed (also, perhaps strafing should be slower?)
    {
        _pos.X -= (float) Math.Cos(_lookDir.X + Math.PI / 2) * moveSpeed;
        _pos.Z -= (float) Math.Sin(_lookDir.X + Math.PI / 2) * moveSpeed;
    }

    if (Keyboard[StrafeRightKey])
    {
        _pos.X += (float)Math.Cos(_lookDir.X + Math.PI / 2) * moveSpeed;
        _pos.Z += (float)Math.Sin(_lookDir.X + Math.PI / 2) * moveSpeed;
    }

    if (Keyboard[MoveBackKey])
    {
        _pos.X -= (float)Math.Cos(_lookDir.X) * moveSpeed;
        _pos.Z -= (float)Math.Sin(_lookDir.X) * moveSpeed;
    }

    if(Keyboard[JumpKey])
    {
        _pos.Y += moveSpeed;
    }

    if (Keyboard[CroucKey])
    {
        _pos.Y -= moveSpeed;
    }

    if (_lockMouse)
    {
        var mouseDelta = Cursor.Position - new Size(_lastMousePos);
        if (mouseDelta != Point.Empty)
        {
            _lookDir.X += mouseDelta.X * _mouseSensitivity;
            _lookDir.Y -= mouseDelta.Y * _mouseSensitivity;
            ResetCursorPosition();
        }
    }

    var target = _pos + new Vector3((float)Math.Cos(_lookDir.X), (float)Math.Sin(_lookDir.Y / 2), (float)Math.Sin(_lookDir.X));
    _viewMat = Matrix4.LookAt(_pos, target, _up);
    _projUniform.Mat4(_viewMat * _projMat);
}

How to lock cursor to game window?

3 Answers3