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POC# Mouse Tracking Drawing Odd Behavior
 

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  1. POC# Mouse Tracking Drawing Odd Behavior
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    <p>I've just made some simple code to track the mouse offset from where Mouse Down to its current position on Mouse Move within a PictureBox. I'm outputting the difference to a label and it works fine.</p> <p>So say I mousedown at X: 20 Y: 20 then move mouse left by 5. My result is X: 15 Y:20.</p> <p>Now the issue is when I take these results (diffX and diffY) and add them to an integer (testOne and testTwo). The result is exponentially different.</p> <p>Most relevant is that when I keep the mouse in the same position without moving it but just holding the button. The results continue to increase.</p> <p>I have reduced my problem to the following code:</p> <pre><code>Point startPoint = new Point(); bool dragging = false; int testOne = 30; int testTwo = 30; private void pictureBox1_MouseMove(object sender, MouseEventArgs e) { if (dragging) { int diffX = (pictureBox1.PointToClient(e.Location).X - startPoint.X); int diffY = (pictureBox1.PointToClient(e.Location).Y - startPoint.Y); label9.Text = diffX.ToString(); //Works, shows desired result label10.Text = diffY.ToString(); //also works fine testOne = (testOne + diffX); //Issue here testTwo = (testTwo + diffY); //and here label11.Text = (testOne).ToString(); //Unexpected results output label12.Text = (testTwo).ToString(); } } private void pictureBox1_MouseDown(object sender, MouseEventArgs e) { if (!dragging) //Incase the mouse down was repeating, it's not { startPoint = pictureBox1.PointToClient(e.Location); dragging = true; } } private void pictureBox1_MouseUp(object sender, MouseEventArgs e) { if (dragging) dragging = false; } </code></pre> <p>I'm using C# WinForms in VS 2008, Framework 3.5</p> <p>any insight would be great, maybe this is a bug or I've simply overlooked something simple. Any ideas or if you can re-produce.</p> <p>Cheers</p> <p>Craig</p>
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    1. USCraig Stewart
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    1. COAlso, there's no threads or loops in my code.
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      1. POC# Mouse Tracking Drawing Odd Behavior
      1. USCraig Stewart
    2. CODo you have issue with how often MouseMove events are fired OR with value that you are calculating? Sum(mouseOffset) does not sound like very useful value by itself...
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      1. POC# Mouse Tracking Drawing Odd Behavior
      1. USAlexei Levenkov
    3. COOT but judging from your code, and if this is for _drawing_, add the drag-points to a list, instead of drawing on the control directly. This allows easy implementation of undo/redo drawing operations.
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