ColorBar <- function(brks = NULL, cols = NULL, vertical = TRUE, 
                     subsampleg = NULL, bar_limits = NULL, var_limits = NULL, 
                     triangle_ends = NULL, col_inf = NULL, col_sup = NULL, 
                     color_fun = clim.palette(), plot = TRUE, 
                     draw_ticks = TRUE, draw_separators = FALSE, 
                     triangle_ends_scale = 1, extra_labels = NULL, 
                     title = NULL, title_scale = 1, 
                     label_scale = 1, tick_scale = 1, 
                     extra_margin = rep(0, 4), label_digits = 4, ...) {
  # Required checks
  if ((is.null(brks) || length(brks) < 2) && is.null(bar_limits) && is.null(var_limits)) {
    stop("At least one of 'brks' with the desired breaks, 'bar_limits' or ",
         "'var_limits' must be provided to generate the colour bar.")
  }

  # Check brks
  if (!is.null(brks)) {
    if (!is.numeric(brks)) {
      stop("Parameter 'brks' must be numeric if specified.")
    } else if (length(brks) > 1) {
      reorder <- sort(brks, index.return = TRUE)
      if (!is.null(cols)) {
        cols <- cols[reorder$ix[which(reorder$ix <= length(cols))]]
      }
      brks <- reorder$x
    } 
  }

  # Check bar_limits
  if (!is.null(bar_limits)) {
    if (!(all(is.na(bar_limits) | is.numeric(bar_limits)) && (length(bar_limits) == 2))) {
      stop("Parameter 'bar_limits' must be a vector of two numeric elements or NAs.")
    }
  }

  # Check var_limits
  if (!is.null(var_limits)) {
    if (!(is.numeric(var_limits) && (length(var_limits) == 2))) {
      stop("Parameter 'var_limits' must be a numeric vector of length 2.")
    } else if (any(is.na(var_limits))) {
      stop("Parameter 'var_limits' must not contain NA values.")
    } else if (any(is.infinite(var_limits))) {
      stop("Parameter 'var_limits' must not contain infinite values.")
    }
  }

  # Check cols
  if (!is.null(cols)) {
    if (!is.character(cols)) {
      stop("Parameter 'cols' must be a vector of character strings.")
    } else if (any(!sapply(cols, .IsColor))) {
      stop("Parameter 'cols' must contain valid colour identifiers.")
    }
  }

  # Check color_fun
  if (!is.function(color_fun)) {
    stop("Parameter 'color_fun' must be a colour-generator function.")
  }

  # Check integrity among brks, bar_limits and var_limits
  if (is.null(brks) || (length(brks) < 2)) {
    if (is.null(brks)) {
      if (is.null(cols)) {
        brks <- 21
      } else {
        brks <- length(cols) + 1
      }
    }
    if (is.null(bar_limits) || any(is.na(bar_limits))) {
      # var_limits is defined
      if (is.null(bar_limits)) {
        bar_limits <- c(NA, NA)
      }
      half_width <- 0.5 * (var_limits[2] - var_limits[1]) / (brks - 1)  
      bar_limits[which(is.na(bar_limits))] <- c(var_limits[1] - half_width, var_limits[2] + half_width)[which(is.na(bar_limits))]
      brks <- seq(bar_limits[1], bar_limits[2], length.out = brks)
    } else if (is.null(var_limits)) {
      # bar_limits is defined
      brks <- seq(bar_limits[1], bar_limits[2], length.out = brks)
      var_limits <- bar_limits
      var_limits[1] <- var_limits[1] + .Machine$double.xmin
    } else {
      # both bar_limits and var_limits are defined
      brks <- seq(bar_limits[1], bar_limits[2], length.out = brks)
    }
  } else if (is.null(bar_limits)) {
    if (is.null(var_limits)) {
      # brks is defined
      bar_limits <- c(head(brks, 1), tail(brks, 1))
      var_limits <- bar_limits
      var_limits[1] <- var_limits[1] + .Machine$double.xmin
    } else {
      # brks and var_limits are defined
      bar_limits <- c(head(brks, 1), tail(brks, 1))
    }
  } else {
    # brks and bar_limits are defined
    # or
    # brks, bar_limits and var_limits are defined
    if (head(brks, 1) != bar_limits[1] || tail(brks, 1) != bar_limits[2]) {
      stop("Parameters 'brks' and 'bar_limits' are inconsistent.")
    }
  }   
  
  # Check col_inf
  if (!is.null(col_inf)) {
    if (!.IsColor(col_inf)) {
      stop("Parameter 'col_inf' must be a valid colour identifier.")
    }
  }  

  # Check col_sup
  if (!is.null(col_sup)) {
    if (!.IsColor(col_sup)) {
      stop("Parameter 'col_sup' must be a valid colour identifier.")
    }
  }

  # Check triangle_ends
  if (!is.null(triangle_ends) && (!is.logical(triangle_ends) || length(triangle_ends) != 2)) {
    stop("Parameter 'triangle_ends' must be a logical vector with two elements.")
  } 
  teflc <- triangle_ends_from_limit_cols <- c(!is.null(col_inf), !is.null(col_sup))
  if (is.null(triangle_ends) && is.null(col_inf) && is.null(col_sup)) {
    triangle_ends <- c(FALSE, FALSE)
    if (bar_limits[1] >= var_limits[1]) {
      triangle_ends[1] <- TRUE
    }
    if (bar_limits[2] < var_limits[2]) {
      triangle_ends[2] <- TRUE
    }
  } else if (!is.null(triangle_ends) && is.null(col_inf) && is.null(col_sup)) {
    triangle_ends <- triangle_ends
  } else if (is.null(triangle_ends) && (!is.null(col_inf) || !is.null(col_sup))) {
    triangle_ends <- teflc
  } else if (any(teflc != triangle_ends)) {
    if (!is.null(brks) && length(brks) > 1 && !is.null(cols) && length(cols) >= length(brks)) {
      triangle_ends <- teflc
    } else if (!is.null(cols)) {
      triangle_ends <- teflc
    } else {
      triangle_ends <- triangle_ends
    }
  }

  # Generate colours if needed
  if (is.null(cols)) {
    cols <- color_fun(length(brks) - 1 + sum(triangle_ends))
    attr_bk <- attributes(cols)
    if (triangle_ends[1]) {
      if (is.null(col_inf)) col_inf <- head(cols, 1)
      cols <- cols[-1]
    }
    if (triangle_ends[2]) {
      if (is.null(col_sup)) col_sup <- tail(cols, 1)
      cols <- cols[-length(cols)]
    }
    attributes(cols) <- attr_bk
  } else if ((length(cols) != (length(brks) - 1))) {
    stop("Incorrect number of 'brks' and 'cols'. There must be one more break than the number of colours.")
  }

  # Check vertical
  if (!is.logical(vertical)) {
    stop("Parameter 'vertical' must be TRUE or FALSE.")
  }

  # Check extra_labels
  if (is.null(extra_labels)) {
    extra_labels <- numeric(0)
  }
  if (!is.numeric(extra_labels)) {
    stop("Parameter 'extra_labels' must be numeric.")
  } else {
    if (any(extra_labels > bar_limits[2]) || any(extra_labels < bar_limits[1])) {
      stop("Parameter 'extra_labels' must not contain ticks beyond the color bar limits.")
    }
  }
  extra_labels <- sort(extra_labels)

  # Check subsampleg
  primes <- function(x) {
    # Courtesy of Chase. See http://stackoverflow.com/questions/6424856/r-function-for-returning-all-factors
    x <- as.integer(x)
    div <- seq_len(abs(x))
    factors <- div[x %% div == 0L]
    factors <- list(neg = -factors, pos = factors)
    return(factors)
  }
  remove_final_tick <- FALSE
  added_final_tick <- TRUE
  if (is.null(subsampleg)) {
    subsampleg <- 1
    while (length(brks) / subsampleg > 15 - 1) {
      next_factor <- primes((length(brks) - 1) / subsampleg)$pos
      next_factor <- next_factor[length(next_factor) - ifelse(length(next_factor) > 2, 1, 0)]
      subsampleg <- subsampleg * next_factor
    }
    if (subsampleg > (length(brks) - 1) / 4) {
      subsampleg <- max(1, round(length(brks) / 4))
      extra_labels <- c(extra_labels, bar_limits[2])
      added_final_tick <- TRUE
      if ((length(brks) - 1) %% subsampleg < (length(brks) - 1) / 4 / 2) {
        remove_final_tick <- TRUE
      }
    }
  } else if (!is.numeric(subsampleg)) {
    stop("Parameter 'subsampleg' must be numeric.")
  }
  subsampleg <- round(subsampleg)

  # Check plot
  if (!is.logical(plot)) {
    stop("Parameter 'plot' must be logical.")
  }

  # Check draw_separators
  if (!is.logical(draw_separators)) {
    stop("Parameter 'draw_separators' must be logical.")
  }

  # Check triangle_ends_scale
  if (!is.numeric(triangle_ends_scale)) {
    stop("Parameter 'triangle_ends_scale' must be numeric.")
  }

  # Check draw_ticks
  if (!is.logical(draw_ticks)) {
    stop("Parameter 'draw_ticks' must be logical.")
  }

  # Check title
  if (is.null(title)) {
    title <- ''
  }
  if (!is.character(title)) {
    stop("Parameter 'title' must be a character string.")
  }

  # Check title_scale
  if (!is.numeric(title_scale)) {
    stop("Parameter 'title_scale' must be numeric.")
  }

  # Check label_scale
  if (!is.numeric(label_scale)) {
    stop("Parameter 'label_scale' must be numeric.")
  }

  # Check tick_scale
  if (!is.numeric(tick_scale)) {
    stop("Parameter 'tick_scale' must be numeric.")
  }

  # Check extra_margin
  if (!is.numeric(extra_margin) || length(extra_margin) != 4) {
    stop("Parameter 'extra_margin' must be a numeric vector of length 4.")
  }

  # Check label_digits
  if (!is.numeric(label_digits)) {
    stop("Parameter 'label_digits' must be numeric.")
  }
  label_digits <- round(label_digits)

  # Process the user graphical parameters that may be passed in the call
  ## Graphical parameters to exclude
  excludedArgs <- c("cex", "cex.axis", "col", "lab", "las", "mar", "mgp", "new", "ps")
  userArgs <- .FilterUserGraphicArgs(excludedArgs, ...)

  #
  #  Plotting colorbar
  # ~~~~~~~~~~~~~~~~~~~
  #
  if (plot) {
    pars_to_save <- c('mar', 'cex', names(userArgs), 'mai', 'mgp', 'las', 'xpd')
    saved_pars <- par(pars_to_save) 
    par(mar = c(0, 0, 0, 0), cex = 1)
    image(1, 1, t(t(1)), col = rgb(0, 0, 0, 0), axes = FALSE, xlab = '', ylab = '')
    # Get the availale space
    figure_size <- par('fin')
    cs <- par('csi')
    # This allows us to assume we always want to plot horizontally
    if (vertical) {
      figure_size <- rev(figure_size)
    }
#    pannel_to_redraw <- par('mfg')
#    .SwitchToFigure(pannel_to_redraw[1], pannel_to_redraw[2])
    # Load the user parameters
    par(new = TRUE)
    par(userArgs)
    # Set up color bar plot region
    margins <- c(0.0, 0, 0.0, 0)
    cex_title <- 1 * title_scale
    cex_labels <- 0.9 * label_scale
    cex_ticks <- -0.3 * tick_scale
    spaceticklab <- max(-cex_ticks, 0)
    if (vertical) {
      margins[1] <- margins[1] + (1.2 * cex_labels * 3 + spaceticklab) * cs
      margins <- margins + extra_margin[c(4, 1:3)] * cs
    } else {
      margins[1] <- margins[1] + (1.2 * cex_labels * 1 + spaceticklab) * cs
      margins <- margins + extra_margin * cs
    }
    if (title != '') {
      margins[3] <- margins[3] + (1.0 * cex_title) * cs
    }
    margins[3] <- margins[3] + sqrt(figure_size[2] / (margins[1] + margins[3])) * 
                               figure_size[2] / 6 * ifelse(title != '', 0.5, 0.8)
    # Set side margins
    margins[2] <- margins[2] + figure_size[1] / 16
    margins[4] <- margins[4] + figure_size[1] / 16
    triangle_ends_prop <- 1 / 32 * triangle_ends_scale 
    triangle_ends_cex <- triangle_ends_prop * figure_size[2]
    if (triangle_ends[1]) {
      margins[2] <- margins[2] + triangle_ends_cex
    }
    if (triangle_ends[2]) {
      margins[4] <- margins[4] + triangle_ends_cex
    }
    ncols <- length(cols)
    # Set up the points of triangles
    # Compute the proportion of horiz. space occupied by one plot unit
    prop_unit <- (1 - (margins[2] + margins[4]) / figure_size[1]) / ncols
    # Convert triangle height to plot inits
    triangle_height <- triangle_ends_prop / prop_unit
    left_triangle <- list(x = c(1, 1 - triangle_height, 1) - 0.5,
                          y = c(1.4, 1, 0.6))
    right_triangle <- list(x = c(ncols, ncols + triangle_height, ncols) + 0.5,
                           y = c(1.4, 1, 0.6))
    # Draw the color squares and title
    if (vertical) {
      par(mai = c(margins[2:4], margins[1]), 
          mgp = c(0, spaceticklab + 0.2, 0), las = 1)
      d <- 4
      image(1, 1:ncols, t(1:ncols), axes = FALSE, col = cols, 
            xlab = '', ylab = '')
      title(ylab = title, line = cex_title * (0.2 + 0.1), cex.lab = cex_title)
      # Draw top and bottom border lines    
      lines(c(0.6, 0.6), c(1 - 0.5, ncols + 0.5))
      lines(c(1.4, 1.4), c(1 - 0.5, ncols + 0.5))
      # Rotate triangles
      names(left_triangle) <- rev(names(left_triangle))
      names(right_triangle) <- rev(names(right_triangle))
    } else {
      # The term - cex_labels / 4 * (3 / cex_labels - 1) was found by
      # try and error
      par(mai = margins, 
          mgp = c(0, cex_labels / 2 + spaceticklab 
                     - cex_labels / 4 * (3 / cex_labels - 1), 0),
          las = 1)
      d <- 1
      image(1:ncols, 1, t(t(1:ncols)), axes = FALSE, col = cols, 
            xlab = '', ylab = '')
      title(title, line = cex_title * (0.2 + 0.1), cex.main = cex_title)
      # Draw top and bottom border lines    
      lines(c(1 - 0.5, ncols + 0.5), c(0.6, 0.6))
      lines(c(1 - 0.5, ncols + 0.5), c(1.4, 1.4))
      tick_length <- -0.4
    }
    # Draw the triangles
    par(xpd = TRUE)
    if (triangle_ends[1]) {
      # Draw left triangle
      polygon(left_triangle$x, left_triangle$y, col = col_inf, border = NA)
      lines(left_triangle$x, left_triangle$y)       
    }
    if (triangle_ends[2]) {
      # Draw right triangle
      polygon(right_triangle$x, right_triangle$y, col = col_sup, border = NA)
      lines(right_triangle$x, right_triangle$y)
    }
    par(xpd = FALSE)

    # Put the separators
    if (vertical) {
      if (draw_separators) {
        for (i in 1:(ncols - 1)) {
          lines(c(0.6, 1.4), c(i, i) + 0.5)
        }
      }
      if (draw_separators || is.null(col_inf)) {
        lines(c(0.6, 1.4), c(0.5, 0.5))
      }
      if (draw_separators || is.null(col_sup)) {
        lines(c(0.6, 1.4), c(ncols + 0.5, ncols + 0.5))
      }
    } else {
      if (draw_separators) {
        for (i in 1:(ncols - 1)) {
          lines(c(i, i) + 0.5, c(0.6, 1.4))
        }
      }
      if (draw_separators || is.null(col_inf)) {
        lines(c(0.5, 0.5), c(0.6, 1.4))
      }
      if (draw_separators || is.null(col_sup)) {
        lines(c(ncols + 0.5, ncols + 0.5), c(0.6, 1.4))
      }
    }
    # Put the ticks
    plot_range <- length(brks) - 1
    var_range <- tail(brks, 1) - head(brks, 1)
    extra_labels_at <- ((extra_labels - head(brks, 1)) / var_range) * plot_range + 0.5
    at <- seq(1, length(brks), subsampleg)
    labels <- brks[at]
    # Getting rid of next-to-last tick if too close to last one
    if (remove_final_tick) {
      at <- at[-length(at)]
      labels <- labels[-length(labels)]
    }
    labels <- signif(labels, label_digits)
    if (added_final_tick) {
      extra_labels[length(extra_labels)] <- signif(tail(extra_labels, 1), label_digits)
    }
    at <- at - 0.5
    at <- c(at, extra_labels_at)
    labels <- c(labels, extra_labels)
    tick_reorder <- sort(at, index.return = TRUE)
    at <- tick_reorder$x
    labels <- labels[tick_reorder$ix]
    axis(d, at = at, tick = draw_ticks, labels = labels, cex.axis = cex_labels, tcl = cex_ticks)
    par(saved_pars)
  }
  invisible(list(brks = brks, cols = cols, col_inf = col_inf, col_sup = col_sup))
}
