Mouse.Synchronize()

Question

What does Mouse.Synchronize() do in .Net?

MSDN says it 'forces the mouse to resynchronize'

Answer 1

Just my assumption:

Similar method exists in Stylus class: Stylus.Synchronize. It should be used together with Stylus.DirectlyOver to ensure that stylus pointer is still above button, although the button was moved somewhere else.

I believe that "Synchronize" is implemented in parent class of both classes: Stylus and Mouse. It's important for Stylus, but it's not necessary for the Mouse. I tried example from Stylus.Synchronize ( I just replaced "Stylus" by "Mouse" ) and it works well also without Mouse.Synchronize(); line.

Answer 2

Well, for what it's worth here is the source code of the method:

public void Synchronize()
{
    PresentationSource criticalActiveSource = this.CriticalActiveSource;
    if (((criticalActiveSource != null) && (criticalActiveSource.CompositionTarget != null)) && !criticalActiveSource.CompositionTarget.IsDisposed)
    {
        InputReportEventArgs args;
        int tickCount = Environment.TickCount;
        Point clientPosition = this.GetClientPosition();
        RawMouseInputReport report = new RawMouseInputReport(InputMode.Foreground, tickCount, criticalActiveSource, RawMouseActions.AbsoluteMove, (int) clientPosition.X, (int) clientPosition.Y, 0, IntPtr.Zero);
        report._isSynchronize = true;
        if (this._stylusDevice != null)
        {
            args = new InputReportEventArgs(this._stylusDevice, report);
        }
        else
        {
            args = new InputReportEventArgs(this, report);
        }
        args.RoutedEvent = InputManager.PreviewInputReportEvent;
        this._inputManager.Value.ProcessInput(args);
    }
}

The important line is:

RawMouseInputReport report = new RawMouseInputReport(InputMode.Foreground, tickCount, criticalActiveSource, RawMouseActions.AbsoluteMove, (int) clientPosition.X, (int) clientPosition.Y, 0, IntPtr.Zero);

According to this, the method is trying to move the mouse to the same position it's already in then analyze the results - here comes my own assumption, that if there's any offset between the previous position and new position, it's stored somewhere and used for any future mouse actions.