PFont f;
XMLElement xml;
int border= 60;
int W = 740 + 2*border;
int H = 400;
String[] years;
String[] democrats ;
String[] republicans;
int wid;
int L;
color r = color(200, 0, 100);
color d = color(0, 0, 255);


void setup()
{
  size(W, H + 2*border);
  smooth();
  f = loadFont("SansSerif-48.vlw");
  
  xml = new XMLElement(this, "http://www.thevioletpiece.com/data/projects/congress/congress.xml");
  XMLElement[] congresses = xml.getChildren("congress");
  L = congresses.length;
  years = new String[L];
  democrats= new String[L];
  republicans = new String[L];
  for(int i = 0; i < L; i++)
  {
    years[i] = congresses[i].getChild("year").getContent();
    democrats[i] = congresses[i].getChild("democrats").getContent();
    republicans[i] = congresses[i].getChild("republicans").getContent();
  }
  wid = 740/congresses.length;
  
  
}

void draw(){
  
  textAlign(LEFT);
  textFont(f,16);
  background(0);
  fill(50);
  rect( border, 30, 360, 15); 
  fill(200, 0, 100);
  text("Lincoln Era", border+100, 43);
  fill(150);
  rect( 360 + border, 30, 240, 15); 
  fill(0, 0, 250);
  text("Roosevelt Era", border+425, 43);
  fill(50);
  rect( 600 + border, 30, 142, 15); 
  fill(200, 0, 100);
  text("Reagan Era", border+625, 43);
  fill(200, 0, 100);
  rect( border, H+border, 740, -H); 
  
  setGradient(27, border, 15, 400, r, d);
  fill(255); 
  text("% D", 19, 56);
  
   for(int i=0; i<L; i++)
   {
    fill(0,0,255);
    Float percent = -H*Float.valueOf(democrats[i].trim()).floatValue()/(Float.valueOf(democrats[i].trim()).floatValue() + Float.valueOf(republicans[i].trim()).floatValue());
    noStroke();
    rect(wid*(i)+border, H+border, wid,  percent); 
    if(i%8 == 4)
    {
      fill(255);
      textAlign(CENTER);
       textFont(f,16);
      text(years[i], wid*(i)+border, border+17+H) ;
    }
   }  
    for(int i=0; i< L; i++)  
    {
      if(mouseX>wid*(i) +border && mouseX < wid*(i+1) + border)
      {
        fill(255);
        rect(wid*(i) + border, border, 1, 400);
        rect(wid*(i+1) + border, border, 1, 400);
        textAlign(LEFT);
        textFont(f,20);
        text( years[i] + "\nD: " +democrats[i] + "\nR: " + republicans[i], mouseX+25, mouseY+40);       
      }
   }  
}

void setGradient(int x, int y, float w, float h, color c1, color c2 ){
  // calculate differences between color components 
  float deltaR = red(c2)-red(c1);
  float deltaG = green(c2)-green(c1);
  float deltaB = blue(c2)-blue(c1);

    for (int i=x; i<=(x+w); i++){
      // row
      for (int j = y; j<=(y+h); j++){
        color c = color(
        (red(c1)+(j-y)*(deltaR/h)),
        (green(c1)+(j-y)*(deltaG/h)),
        (blue(c1)+(j-y)*(deltaB/h)) 
          );
        set(i, j, c);
      }
    }    
}