/** 
  * Bandscope Receiver Applet 1.0.0 ["LISTENING ON" PANEL]
  * @author Robert J Morton <robmorton@clara.net> YE572246C
  * @version 13 March 2002, 20 March 2012
  * @copyright Robert J Morton (all rights reserved) */

import javax.swing.*;  // swing widgets
import java.awt.*;     // for graphics operations (GUI)

class listeningon extends JPanel {
  private int 
    W,      // width of the "listening on" panel
    H,      // Height of "listening on" frequency panel
    I = 5;  // text inset from beginning of text area

  private int
    J,   // end position for right-justified text
    tb,  // text base line for panel of height H
    rF,  // receiving frequency in integral half-kHz
    rX;  // x-coordinate of the "listening on" line on the scope graph

  private String rFs;         // receiving frequency rF in String form
  private boolean receiving;  // true = listening on a specified frequency
  private Color bg;           // panel background colour
  private Font font;          // font used in this panel
  private FontMetrics fm;     // font metrics of the current font

  private scope sc;      // reference to the scope object
  private mousefreq mf;  // reference to the mouse frequency panel object
  private ar86000 rx;    // reference to the receiver object


  listeningon(Color bg, Font font, mousefreq mf, int W, int H) {
    this.bg = bg;  // set panel colour
    this.mf = mf;  // reference to mouse frequency panel class instance
    this.W = W;    // width of listening-on panel class instance
    this.H = H;    // width of listening-on panel class instance
    J = W - I;
    this.font = font;
    fm = getFontMetrics(font);  // get dimensions of current type face

    // y-coordinate for lettering within a field of depth H
    tb = fm.getAscent() + (H - fm.getHeight()) / 2;
  }



  void setScope(scope sc) {  // Enables an external class to set ref-
    this.sc = sc;            // erence to scope panel class instance.
  }


  void setAR86000(ar86000 rx) {  // Enables an external class to set ref-
    this.rx = rx;                // erence to receiver class instance.
  }


  void click(int x) {   // MOUSE CLICK EVENT HANDLER
    rX = x;             // x-coordinate of mouse within scope area
    atualizar();        // (0 = left edge of scope)
  }


  void inchFreq(int δx) {  // INCHING EVENT FROM THE UP/DOWN BUTTONS
    rX += δx;  // add + or - 1 to current x-coordinate of highlighted bar
    if(sc.withinScopeWidth(rX)) {  // provided inched x-coordinate is still 
      atualizar(); }               // within scope area, update it.
  }


  private void atualizar() {
    rF = mf.pixTokHz(rX);  // convert x-coordinate to half-kHz

    /* Use 3 decimal places of MHz, however, if frequency is less tha
       100MHz, use 4 decimal places of MHz. */
    int q = 3; if(rF < 200000) q = 4;

    // convert to a string of 3 or 4 decimal places of MHz
    rFs = convert.toMHz(rF, q) + " MHz";

    sc.highlightSignal(rX);  // highlight the listening frequency 
                             // in blue on the scope panel
    setReceiving(true);      // indicate that receiver is being 
                             // tuned to the listening frequency
    repaint();  // shedule a repaint via the event-despatching thread
  }


  // DISPLAY THE FREQUENCY AT WHICH THE MOUSE WAS CLICKED
  public void paint(Graphics g) {

    // clear 'Listening on' area to the panel background colour
    g.setColor(bg); g.fillRect(0, 0, W, H);

    /* Probided we are actually listening on the clicked frequency,
    set the font to print in black then display the "Listening on"
    label and the frequency on which we are listening. */

    if(receiving) {
      g.setFont(font); g.setColor(Color.black);
      g.drawString("Listening on:", I, tb);
      g.drawString(rFs, J - fm.stringWidth(rFs), tb);
    }
  }


  boolean getReceiving() {return receiving;}  // CALLED ONLY BY "SCOPE"


  // CALLED BY "BANDS", "CENTREFREQ" AND "FREQSPAN"
  void setReceiving(boolean b) {
    receiving = b;  // set the "receiving or not" state

    /* If currently receiving (listening-on), send 'tune to' 
    command to the receiver; otherwise, mute the receiver. */

    if(receiving) rx.tuneTo(rF * 500); else rx.mute();
  }
}