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  How to show the chart legend in one single line
Posted by moses on Jan-29-2024 21:32
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I want to show the legend box in one single line, if there are many legend items, I want to show only one line and ignore others.
I use the function pChart->addLegend(legendRect.x, legendRect.y, false, cTextBoxFont.strFontName, cTextBoxFont.nSize) to create the legend and the function legend->setHeight(legendRect.nHeight) to set height for the legend, but it doesn't work.

  Re: How to show the chart legend in one single line
Posted by Peter Kwan on Jan-30-2024 22:39
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Hi Moses,

You can use Layer.setLegendOrder to disable automatic legend entries for a layer. However, for your case, I assume you cannot determine how many legend entries to keep to ensure they fit on one line.

After some thoughts, I think you can draw the legend entries with your own code. Some of our sample code use this method. One example is as follows:

https://www.advsofteng.com/doc/cdcpp.htm#tracklegend.htm

For your case, we just need to keep the part that draws the legend entries, and I come up with the following subroutine:


std::string getLegendText(XYChart* c)
{
    std::string legendText;

    // Iterate through all layers to build the legend array
    for (int i = 0; i < c->getLayerCount(); ++i) {
        Layer* layer = c->getLayerByZ(i);

        // Iterate through all the data sets in the layer
        for (int j = 0; j < layer->getDataSetCount(); ++j) {
            DataSet* dataSet = layer->getDataSetByZ(j);

            // We are only interested in visible data sets with names
            const char* dataName = dataSet->getDataName();
            int color = dataSet->getDataColor();
            if (dataName && *dataName && (color != Chart::Transparent)) {
                std::string legendEntry = std::string("<*block*>") + dataSet->getLegendIcon() + dataName + "<*/*>";
                if (!legendText.empty())
                    legendText = "        " + legendText;
                legendText = legendEntry + legendText;
            }
        }
    }

    return legendText;
}


It can be used as follows:

... Build the chart as usual, without adding a legend box ...

// Get the legend entries as a CDML text string
std::string legendText = getLegendText(c);

// Add the legend text to the chart as a TextBox
TextBox* myLegendBox = c->addText(legendRect.x, legendRect.y, legendText.c_str(), cTextBoxFont.strFontName, cTextBoxFont.nSize);

// Limit the length to maxWidth, and limit the line to 1 line
myLegendBox->setTruncate(maxWidth, 1);

... You can use Box::setBackground to configure the background and border colors of the TextBox. ...


Best Regards
Peter Kwan