DragMove() problem, help pls!

Question

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Hi,

Ok, my problem is about DragMove() method in WPF, when I use this method on MouseLeftButtonDown event, after it don't work other commands OnMouseLeftButtonUp event.

Please tell me how to show the message after DragMove.

C#

public partial class myWindow : Window
{
    public myWindow()
    {
        this.InitializeComponent();
    }

    protected override void OnMouseLeftButtonDown(MouseButtonEventArgs e)
    {
        DragMove();
        base.OnMouseLeftButtonDown(e);
    }

    protected override void OnMouseLeftButtonUp(MouseButtonEventArgs e)
    {
        MessageBox.Show("this is a test");
        base.OnMouseLeftButtonUp(e);
    }
}

In addition, I tried to simulate the DragMove, but it doesn't work correctly! actually, when I move the window to around quickly, it don't remain with cursor!

C#

public partial class myWindow : Window
{
    public myWindow()
    {
        this.InitializeComponent();

        inDrag = false;
    }

    bool inDrag;
    Point dragPoint;

    protected override void OnMouseLeftButtonDown(MouseButtonEventArgs e)
    {
        dragPoint = e.GetPosition(this);
        inDrag = true;
    }

    protected override void OnMouseMove(MouseEventArgs e)
    {
        if (inDrag)
        {
            Point pointMoveTo;

            // Find the current mouse position in screen coordinates.
            pointMoveTo = this.PointToScreen(e.GetPosition(this));

            // Compensate for the position the control was clicked.
            pointMoveTo.Offset(-dragPoint.X, -dragPoint.Y);

            // Compensate for the non-client region (title bar).
            // This code is not necessary if you explicitly hide the title bar
            //  by setting the form's BorderStyle to None.
            //pointMoveTo.Offset(0, -25);

            // Move the window.
            this.Left = pointMoveTo.X;
            this.Top = pointMoveTo.Y;
        }
        base.OnMouseMove(e);
    }

    protected override void OnMouseLeftButtonUp(MouseButtonEventArgs e)
    {
        inDrag = false;

        MessageBox.Show("this is a test");
        base.OnMouseLeftButtonUp(e);
    }
}

Any help is appreciated.

Thanks in advance.

Posted 16-Nov-11 2:49am

hzawary

Updated 16-Nov-11 4:00am

RaisKazi

v2

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Comments

Mark Salsbery 16-Nov-11 11:09am

Yes DragMove blocks and consumes the mouseup event. Yes you are still calculating coordinates incorrectly as I stated repeatedly in your last thread on this topic :)

hzawary 16-Nov-11 11:14am

please, you tell me about this, what should to do?

hzawary 16-Nov-11 11:20am

In this simple Dragmove, What's your solution?

hzawary 16-Nov-11 11:22am

You can write this simple dragmove for me?

hzawary 16-Nov-11 11:31am

Do you test this codes?!, If the coordinates are incorrect, you write it correctly please?

Mark Salsbery 16-Nov-11 11:49am

You can't rely on GetPosition(this) to work. Yes, it may work when dragging slowly, but does it really work? You are positioning a window while getting coordinates of the cursor relative to the same window that is moving - that's likely to not work so well. You need to use GetPosition(parentofthis) so you are getting coordinates relative to the element you are positioning the window on. If the window is the topmost element then screen coordinates are what you'd want so you could probably do something like this

PointToScreen(e.GetPosition(this))

hzawary 16-Nov-11 12:26pm

You can solve the problem completely? (A simple question: Dragging a wpf window without titlebar like DragMove() method, that MouseUp it is working correctly).

Mark Salsbery 16-Nov-11 12:31pm

Your code should work if you get the correct cursor coordinates (where you make the GetPosition() calls) - that's what I'm saying. I use similar code all the time for allowing the user to drag elements around.

hzawary 16-Nov-11 12:49pm

May you give me your code in wpf?

Member 12351612 11-Mar-16 11:11am

I eventually felt on a work around, it seems that implementing an empty MouseLeave handler fixes the issue. My code is :

(Constructor:)
MouseDown += RTCM_Win_OnMouseDown;
MouseLeave += RTCM_Win_OnMouseLeave;
(Handlers:)

private void RTCM_Win_OnMouseDown(object sender, MouseButtonEventArgs e)
{
if (e.ChangedButton == MouseButton.Left)
this.DragMove();
}

private void RTCM_Win_OnMouseLeave(object sender, MouseEventArgs e)
{
// Work hard !
}

3 solutions

Solution 3

This is a solution in addition to Mark Salsbery's. His code works, but when you have a control on the area that your window is dragged when you perform a mousedown, it's events don't work because the CaptureMouse() function blocks it.

For example, I have a "close" button (which is actually a label), but it's mousedown event won't work because the CaptureMouse() function somehow blocks it.

Solution is to use capturemouse function in the "OnMouseMove" event. So if mouse doesn't move after mousedown event, capturemouse will not block other controls' events.

C#

private bool inDrag = false;
private Point anchorPoint;

private bool iscaptured = false;

protected override void OnMouseLeftButtonDown(MouseButtonEventArgs e)
{
	anchorPoint = PointToScreen(e.GetPosition(this));
	inDrag = true;
}

protected override void OnMouseMove(MouseEventArgs e)
{
	if (inDrag) {
		if (!iscaptured) {
			CaptureMouse();
			iscaptured = true;
		}
		Point currentPoint = PointToScreen(e.GetPosition(this));
		this.Left = this.Left + currentPoint.X - anchorPoint.X;
		this.Top = this.Top + currentPoint.Y - anchorPoint.Y;
		anchorPoint = currentPoint;
	}
}

protected override void OnMouseLeftButtonUp(MouseButtonEventArgs e)
{
	if (inDrag) {
		inDrag = false;
		iscaptured = false;
		ReleaseMouseCapture();
	}
}

Posted 19-Mar-15 16:17pm

MuhsinFatih

Solution 2

This might be a little old but I ran into a similar issue recently and adapted a solution on a similar issue to enable this to work without a jerky motion. Using the PreviewMouseLeftButtonDown and PreviewMouseMove events, you compare the initial point and current point and only call DragMove when the mouse actually starts moving.

C#

private Point startPoint;
private void Window_PreviewMouseLeftButtonDown(object sender, MouseButtonEventArgs e)
{
    startPoint = e.GetPosition(this);
}

private void Window_PreviewMouseMove(object sender, MouseEventArgs e)
{
    Point newPoint = e.GetPosition(this);
    if (e.LeftButton == MouseButtonState.Pressed && (Math.Abs(newPoint.X - startPoint.X) > SystemParameters.MinimumHorizontalDragDistance ||
        Math.Abs(newPoint.Y - startPoint.Y) > SystemParameters.MinimumVerticalDragDistance))
    {
        this.DragMove();
    }
}

Posted 21-Feb-14 11:06am

Member 10338758

Comments

hzawary 23-Feb-14 5:27am

Oh, yes it is old story! thanks for your solution, but now I try below code and it is in correct. Perhaps, because I having use VisualStudio2012 in Windows8.1. Maybe Microsoft solved the bug, I don't know, just I know that now is work correctly and suggestion for you this simple code to drag the window.

public partial class myWindow : Window
{
public myWindow()
{
this.InitializeComponent();
}

protected override void OnMouseLeftButtonDown(MouseButtonEventArgs e)
{
DragMove();
base.OnMouseLeftButtonDown(e);
}

protected override void OnMouseLeftButtonUp(MouseButtonEventArgs e)
{
MessageBox.Show("this is a test");
base.OnMouseLeftButtonUp(e);
}
}

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Mark Salsbery · Accepted Answer · 2011-11-16T06:50:00

Here's an example I ripped from my examples posted here[^] and here[^]...maybe it will work.

C#

public partial class myWindow : Window
{
    public myWindow()
    {
        this.InitializeComponent();
    }

    bool inDrag = false;
    Point anchorPoint;

    protected override void OnMouseLeftButtonDown(MouseButtonEventArgs e)
    {
        anchorPoint = PointToScreen(e.GetPosition(this));
        inDrag = true;
        CaptureMouse();
        e.Handled = true;
    }

    protected override void OnMouseMove(MouseEventArgs e)
    {
        if (inDrag)
        {
            Point currentPoint = PointToScreen(e.GetPosition(this));
            this.Left = this.Left + currentPoint.X - anchorPoint.X;
            this.Top = this.Top + currentPoint.Y - anchorPoint.Y;
            anchorPoint = currentPoint;
        }
    }

    protected override void OnMouseLeftButtonUp(MouseButtonEventArgs e)
    {
        if (inDrag)
        {
            ReleaseMouseCapture();
            inDrag = false;
            e.Handled = true;
        }
    }
}