Question

If you place a panel in a new C# project and capture it’s MouseMove event like this:

private void panel1_MouseMove(object sender, MouseEventArgs e)
{
    if (e.Button != MouseButtons.Left)
        return;

    Console.WriteLine("e.X: {0}, e.Y: {1}", e.X, e.Y);
}

It tells you the client coordinates of the mouse while the left mouse button is held down, even if the cursor goes outside of the panel.

However, if you are holding down left mouse button in the container and then, while holding down left mouse button, click any other mouse button on your mouse, it no longer calls MouseMove while outside the bounds of the container.

Is there any way to change this? Thanks for reading.

Answer 1

1: If you are trying to get it to work only when the left button is down, try the following:

bool mouseDown = false;

private void panel1_MouseMove(object sender, MouseEventArgs e)
{
    if (!mouseDown)
        return;

    Console.WriteLine("e.X: {0}, e.Y: {1}", e.X, e.Y);
}

private void panel1_MouseDown(object sender, MouseEventArgs e)
{
    if (e.Button == MouseButtons.Left)
        mouseDown = true;
}

private void panel1_MouseUp(object sender, MouseEventArgs e)
{
    if (e.Button == MouseButtons.Left)
        mouseDown = false;
}

2: Otherwise, if you want it to work when any mouse button is down, try the following:

int mouseDown = 0;

private void panel1_MouseMove(object sender, MouseEventArgs e)
{
    if (mouseDown == 0)
        return;

    Console.WriteLine("e.X: {0}, e.Y: {1}", e.X, e.Y);
}

private void panel1_MouseDown(object sender, MouseEventArgs e)
{
    mouseDown++;
}

private void panel1_MouseUp(object sender, MouseEventArgs e)
{
    mouseDown--;
}