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POTimer problem with GDI+
 

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  1. POTimer problem with GDI+
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    <p>I am currently stuck at a really strange problem with GDI and timers. </p> <p>First the Code:</p> <pre><code>class Graph : UserControl { private System.Threading.Timer timer; private int refreshRate = 25; //Hz (redrawings per second) private float offsetX = 0; //X offset for moving graph public Graph() { timer = new System.Threading.Timer(timerTick); } private void timerTick(object data) { offsetX -= 1 / refreshRate; this.Invalidate(); } public void timerStart() { timer.Change(0, 1000 / refreshRate); } private void onPaint(object sender, PaintEventArgs e) { //350 lines of code for drawing the graph //Here the offsetX will be used to move the graph } } </code></pre> <p>I am trying here to move a painted graph in a specific time to 1 "graph unit" to the left. So i use a timer which will change the offset in little steps, so it will be a smooth moving (thats the refreshRate for).</p> <p>At the first view this code worked, but later i found following problem: If i am using a refreshRate of 1 (1Hz) it will just fine move my graph in 1 step 1 (graph unit) to the left. If i am increasing the refreshRate my movement will slow done. At 20 FPS its slighly slow, at 200 FPS its really slow.. </p> <p>So here is what i tried:</p> <ol> <li><p>I used Refresh or Update instead of Invalidate</p></li> <li><p>I used a normal Thread (with Sleep) instead of the timer</p></li> </ol> <p>Both code changes didnt changed the result..</p> <p>Beside the movement with the timer I also can move the graph with my mouse and if the timer is running i can still smoothly move the graph with my mouse. So its not a peformance problem..</p> <p>I thought of a problem in the painting queue, because I am refreshing faster than the painting is done? (But why can I sill move the graph smoothly with my mouse?!)</p> <p>So i need a little help here. Thanks</p>
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    1. CO`offsetX -= 1 / refreshRate;` Is that the actual code? Because this is doing an integer division and can only result in 1 or 0...
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      1. USThomas
    2. COno, thats the actual code: `graphOffset.X -= step / (float)refreshRate;` where graphOffset is PointF, step is float and refreshRate is int.. i also thought about this problem (or a rounding problem somewhere in my code)
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    3. COThreading timers and UIs don't normally mix. Is Invalidate safe to call from a non UI thread?
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