How to catch mouse button events in another thread

Question

I am a newbie in WinForms and I have question about MouseDown and MouseUp events (sorry, if I duplicate it, but I cann't google it). So, I have a PictureBox and paint cube on it. But I need to rotate it, using the mouse. I use auto-generated events MouseDown, MouseUp, MouseMove. First of them just change bool variable (it's stupid way to check, but I cann't find the better one).

    private void PictureBox_MouseDown(object sender, MouseEventArgs e)
    {
        RMBIsPressed = true;
    }

    private void PictureBox_MouseUp(object sender, MouseEventArgs e)
    {
        RMBIsPressed = false;
    }

In MouseMove I have do {} while(), that checks state of RMBIsPressed and repaint cube, if it's need.

    private void PictureBox_MouseMove(object sender, MouseEventArgs e)
    {
        Point mousePoint = MousePosition;
        Point mousePointNext;
        do
        {
            mousePointNext = MousePosition;
            if (mousePointNext != mousePoint)
            {
                if (mousePoint.X < mousePointNext.X)
                {
                    teta += deltaTeta;
                }
                else
                {
                    teta -= deltaTeta;
                }
                if (mousePoint.Y < mousePointNext.Y)
                {
                    phi += deltaPhi;
                }
                else
                {
                    phi -= deltaPhi;
                }
                PictureBox.Refresh();                    
                ViewTransformation();
                DrawCube();
            }
            mousePoint = MousePosition;
        } while (RMBIsPressed);
    }

When MouseUp event happens first time, everything is all right, but in next iteration RMBIsPressed is still true, even if I release RMB. It seems do while blocks the MouseUp event. My question is: can I create another thread, which will catch MouseUp and MouseDown events and change value of RMBIsPressed? If it's possible, please tell me how.

Why do you have a loop in your MouseMove handler? That handler is called every time the mouse is moved. This code will most likely completely lock up your UI. — vesan, Oct 01 '15 at 01:14

score 2 · Accepted Answer · answered Oct 01 '15 at 00:45

2

The do-while loop is not letting events being processed.

Rename mousePoint to lastPosition and make it an instance variable.
Set lastPosition in MouseDown and at end of MouseMove.
Remove do-while in MouseMove

I would also change PictureBox.Refresh to PictureBox.Invalidate. This will avoid flicker when mouse is moving very fast.

answered Oct 01 '15 at 00:45

Richard Schneider

34,944
9
57
73

1

No idea why someone downvoted this. This is the way it should be done. You may also want to consider mentioning the 4th thing, that the code isn't checking for _which_ button is pressed, but the variable makes it seem like that's what's desired. – theB Oct 01 '15 at 01:17
Thanks a lot, it helped. It's strange, `PictureBox.Invalidate` don't clear `PictureBox`. I paint cube, using `Graphics.FromImage(PictureBox.Image)` and `DrawLine`. – QuarK Oct 01 '15 at 09:16

score -1 · Answer 2 · answered Oct 01 '15 at 00:50

-1

At the end of your do {} call Application.DoEvents(). That will process the windows messages in the buffer, which means the mouse up event will get processed. You might also want to capture the mouse in mouse down.

answered Oct 01 '15 at 00:50

Lorek

855
5
11

How to catch mouse button events in another thread

2 Answers2