Snippet of code for LCD display of bar graph

I thought I would document this snippet of code which shows an elegant way to draw a line and bar chart. At the moment it draws a fixed bar chart of BARS (defined as 10) bars, with the heights in the array barht[], obviously these values can be dynamically changed by your application, for example by an FFT of an audio input to give a spectrum...

The bar spacing and bar width are calculated depending on the number of bars (n) passed to the barchart() display function.

There is currently no vertical scale but this could be added...


Code

#include "U8glib.h"

// SPI SCK-EN, MOSI-RW & SS-CS
#define EN 13
#define RW 11
#define CS 10

// display set up, bar, line position L & R
#define BARWDTH 5
#define LINEY 50
#define LINEXL 4
#define LINEXR 124
#define BARS 10

U8GLIB_ST7920_128X64_1X lcd(EN, RW, CS); // serial use, PSB = GND


void setup()
{  
  lcd.begin(); // init display
  lcd.setRot180(); // flip screen
}

void loop()
{
  int barht[BARS] = {5, 10, 20, 30, 40, 30, 20, 10, 5, 3}; // ht of the BARS bars
  
  // ... other code
  
  
  barchart(BARS, barht); // draw HT bars display
}

// plot line and bar at position and height
void barchart(int n, int bh[])
{
  int i, s, w; // bars, spacing and width
  
  s = (LINEXR - LINEXL) / n;
  w = s / 2;
  
  lcd.firstPage();
  do
  {
    lcd.drawLine(LINEXL, LINEY, LINEXR, LINEY);
    
    for(i = 0; i < n; i++)
    {
      lcd.drawBox(LINEXL + s * i, LINEY - bh[i], w, bh[i]);
    }
      
  }while(lcd.nextPage()); 
}

I just discovered that the lcd.drawBox(...) function gets mighty confused if the last term is 0 (zero). So any implementation should make sure that is is at least 1.