Teechart PHP CalcXPos返回0

Question

I've been trying to use Teechart to draw a couple of graphs for a project. I've managed to draw the graphs just fine. What I am struggling with is annotating specific points on the graph with some labels.

The specific problem is that when I use $chart1->CalcXPos(someIndex); it always returns 0 instead of a value of the pixels. How can I got about resolving this?

    $chart1 = new TChart(640,480);

    $varname = new Line($chart1->getChart()); 

    $someYValues = array(2,3,5,7,11,13);
    $theXValues = array(-3,-1,1,3,4,5);

    $i=0;
    foreach($someYValues as $x){
        $varname->addXY($theXValues[$i],$someYValues[$i]);
        $i++;
    }        

    $varname->Setcolor(Color::BLUE()); 
    $chart1->getAxes()->getBottom()->getTitle()->setText("X-axis label (units)"); 
    $chart1->getAxes()->getLeft()->getTitle()->setText("Y-axis label (units)"); 

    $tool=new Annotation($chart1->getChart());
    $tool->getShape()->setCustomPosition(true);

    //$chart1->paint;

    $xvalue = $chart1->getAxes()->getBottom()->CalcXPosValue($theXValues[2]);
    $yvalue = $chart1->getAxes()->getLeft()->CalcYPosValue($someYValues[2]);

    //$xvalue = $varname->CalcXPosValue($theXValues[2]);
    //$yvalue = $varname->CalcYPosValue($someYValues[2]);

    echo $xvalue;
    echo $yvalue;

    $tool->setTop($xvalue);
    $tool->setLeft($yvalue);

    $tool->setText("Random Text ");

    $chart1->render("ecg.png");

Answer 1

在使用Calc*函数之前，尝试强制图表重绘：

$chart1->doInvalidate();