[Ginto8]

I actually wrote a little extension for my team that replaces Label and can read values from a NetworkTable, inserting them into a string. I don't know if C++ has a NetworkTable implementation, but if so this might be helpful.

Most of the properties are self-explanatory, but two things you want to keep in mind:

• Network Table is the name of the chosen network table. To access it on the robot side, use NetworkTable.getTable("My table name"). The robot-end and SmartDashboard-end names must be the same for this to work.
• The format string acts like a normal label string, except that everything within % symbols is treated as a key, and gets replaced with the contents of that NetworkTable entry. For example, a format string "Shooter speed: %shooter.rpm%rpm" will display as "Shooter speed: 50000rpm" when your motor is about to explode.

And now, the code:

package storm.smartdashboard;

import edu.wpi.first.smartdashboard.gui.StaticWidget;
import edu.wpi.first.smartdashboard.properties.*;
import edu.wpi.first.wpilibj.networking.NetworkTable;
import java.awt.BorderLayout;
import java.awt.Color;
import javax.swing.JLabel;

/**
 * @author Joe Doyle (Ginto8)
 */
public class SmartLabel extends StaticWidget {
    public static final String NAME = "Smart Label";
    private static NetworkTable SMARTDASHBOARD_FEEDBACK;
    
    private static String format(String s, boolean plusPositive) {
        String ret = "";

        int start = 0, end = 0;
        while (true) {
            start = s.indexOf("%", end);
            if (start < 0) {
                break;
            }
            ret += s.substring(end, start);
            end = s.indexOf("%", start + 1);
            if (end < 0) {
                end = start;
                break;
            }
            String key = s.substring(start + 1, end);
            Object value = SMARTDASHBOARD_FEEDBACK.getValue(key, null);
            if (value == null) {
                ++end;
                ret += s.substring(start, end);
                continue;
            }
            String out = value.toString();
            if (plusPositive) {
                Double asDouble = (Double) value;
                Integer asInteger = (Integer) value;
                if (value instanceof Double && asDouble.doubleValue() >= 0) {
                    out = "+" + out;
                } else if (value instanceof Integer && asInteger.intValue() >= 0) {
                    out = "+" + out;
                }
            }
            ret += out;
            ++end;
            start = end;
        }
        ret += s.substring(end);

        return ret;
    }

    public final StringProperty netTable = new StringProperty(this, "Network Table","Feedback");
    public final StringProperty text = new StringProperty(this, "Format String", "%DEFAULT%");
    public final DoubleProperty fontSize = new DoubleProperty(this,"Font Size",12);
    public final BooleanProperty plusPositive = new BooleanProperty(this,"Always show sign",false);
    public final MultiProperty horizontal = new MultiProperty(this, "Horizontal Alignment");
    public final MultiProperty vertical = new MultiProperty(this, "Vertical Alignment");
    public final ColorProperty textColor = new ColorProperty(this,"Text Color",Color.black);
    private volatile JLabel label;
    Thread updateThread;

    public SmartLabel() {
        this.horizontal.add("Left", Integer.valueOf(2));
        this.horizontal.add("Center", Integer.valueOf(0));
        this.horizontal.add("Right", Integer.valueOf(4));
        this.horizontal.setDefault("Center");

        this.vertical.add("Up", Integer.valueOf(1));
        this.vertical.add("Center", Integer.valueOf(0));
        this.vertical.add("Down", Integer.valueOf(3));
        this.vertical.setDefault("Center");

        updateThread = new Thread() {
            @Override
            public void run() {
                while(true) {
                    update();
                    try {
                        Thread.sleep(1000 / 5);
                    } catch (InterruptedException ex) {

                    }
                }
            }
        };
    }

    private synchronized void update() {
        this.label.setText(format(this.text.getValue(),plusPositive.getValue()));
    }

    @Override
    public void init() {
        setLayout(new BorderLayout());

        SMARTDASHBOARD_FEEDBACK = NetworkTable.getTable(netTable.getValue());

        this.label = new JLabel(format(this.text.getValue(),plusPositive.getValue()));

        this.label.setHorizontalAlignment(((Integer) this.horizontal.getValue()).intValue());
        this.label.setVerticalAlignment(((Integer) this.vertical.getValue()).intValue());
        
        this.label.setFont(label.getFont().deriveFont(fontSize.getValue().floatValue()));
        this.label.setForeground(this.textColor.getValue());

        add(this.label, "Center");

        updateThread.start();
    }

    @Override
    public void propertyChanged(Property property) {
        if (property == this.text || property == plusPositive) {
            update();
        } else if(property == this.fontSize) {
            this.label.setFont(label.getFont().deriveFont(fontSize.getValue().floatValue()));
        } else if (property == this.horizontal) {
            this.label.setHorizontalAlignment(((Integer) this.horizontal.getValue()).intValue());
        } else if (property == this.vertical) {
            this.label.setVerticalAlignment(((Integer) this.vertical.getValue()).intValue());
        } else if(property == this.textColor) {
            this.label.setForeground(this.textColor.getValue());
        } else if(property == this.netTable) {
            SMARTDASHBOARD_FEEDBACK = NetworkTable.getTable(netTable.getValue());
        }
    }
}