Form.MouseDown with non-rectangular Forms inside MDI container?

[Doc John]

I created a non-rectangular Windows Form which opens inside of an MDI
container and I'm managing the MouseMove and MouseDown events with the
following code. The problem is that when I click on the mouse button so that
I can move the Form, the Form "jumps" about an inch to the bottom. This only
happens when the Form opens up inside an Mdi.

private Point mouse_offset;
private void Form1_MouseDown(object sender,
System.Windows.Forms.MouseEventArgs e)
{
mouse_offset = new Point(-e.X, -e.Y);
}
private void Form1_MouseMove(object sender,
System.Windows.Forms.MouseEventArgs e)
{
if (e.Button == MouseButtons.Left)
{
Point mousePos = Control.MousePosition;
mousePos.Offset(mouse_offset.X, mouse_offset.Y);
Location = mousePos;
}
}

Any help is appreciated. Thanks.
VS2005

 

[Peter Duniho]

I created a non-rectangular Windows Form which opens inside of an MDI
container and I'm managing the MouseMove and MouseDown events with the
following code. The problem is that when I click on the mouse button so that
I can move the Form, the Form "jumps" about an inch to the bottom. This only
happens when the Form opens up inside an Mdi.

Probably because the mouse coordinates used in the MouseDown method
aren't the same as those used in the MouseMove method.

 

[Doc John]

It does. MouseDown initializes mouse_offset. And MouseMove then works with
mouse_offset.

 

[Peter Duniho]

It does. MouseDown initializes mouse_offset. And MouseMove then works with
mouse_offset.

It does what?

What you wrote above is true. But it ignores the fact that in
MouseDown, you are using the coordinates passed to you in the event,
while in MouseMove you are using coordinates obtained from the
Control.MousePosition property. These are not necessarily the same, and
the behavior you describe pretty much proves that they aren't in your
scenario.

You should at least try changing your code based on my suggestion,
before you dismiss it.

Pete

 

[Doc John]

Sorry about that.

What would you suggest? I've modified the code in as many ways as I could,
but nothing seems to work.

Thanks again.

 

[Peter Duniho]

Sorry about that.

What would you suggest? I've modified the code in as many ways as I could,
but nothing seems to work.

Have you tried anything like this?

private Point mouse_initial;
private Point form_initial;
private void Form1_MouseDown(object sender,
System.Windows.Forms.MouseEventArgs e)
{
mouse_initial = e.Location;
form_initial = Location;
}
private void Form1_MouseMove(object sender,
System.Windows.Forms.MouseEventArgs e)
{
if (e.Button == MouseButtons.Left)
{
Location = form_initial + (e.Location - mouse_initial);
}
}

 

[Linda Liu [MSFT]]

Hi Doc,

I agree with Peter that the reason of your problem is that in the MouseDown
event you are using the coordinates passed in the event args, while in the
MouseMove event, you are using coordinates obtained from the
Control.MousePosition property.

You should use the coordinates passed in the MouseMove event args as well.
The following is a sample.

Point downPoint = Point.Empty;

void MainForm_MouseDown(object sender, MouseEventArgs e) {
if( e.Button != MouseButtons.Left ) return;
downPoint = new Point(e.X, e.Y);
}

void MainForm_MouseMove(object sender, MouseEventArgs e) {
if( downPoint == Point.Empty ) return;
Point location =
new Point(
this.Left + e.X - downPoint.X,
this.Top + e.Y - downPoint.Y);
this.Location = location;
}

void MainForm_MouseUp(object sender, MouseEventArgs e) {
if( e.Button != MouseButtons.Left ) return;
downPoint = Point.Empty;
}

Hope this helps.
If you have any question, please feel free to let me know.

Sincerely,
Linda Liu
Microsoft Online Community Support

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[Doc John]

Yes. That worked.

Thanks.