Color Mixer

[AnHardt]

Idea for a steady colour mix:

reset_color_bresenham( ) {
  //called at the end of setup_color_bresenham(), and from step_colour_bresenham().
  //reset the line ready to draw the first point 
  //set colour_step to the length of the leading axis;
}

setup_color_bresenham( colourmix[EXTRUDERS] ) {
  //Called when the color is changed. Other virtual tool, or set colour, or changed E parameters.
}

uint8_t step_colour_bresenham() {
  Called from get_extruder().
  Make a step. return a bitmask for the steppers who stepped.
  If at the end of the line reset_colour_bresenham()
}

uint8_t get_extruder(void) {
  //Called whenever an E-step is needed - forwards and backwards.
  //Returns the index of a stepper.
  static uint8_t stack = 0;
  static uint8:t b = 0;
  do {
    while (stack) {
        if (stack & 1) {
         stack= stack>>1;
         return b++;  // steps could also be executed here, but pulse time cant be used for anything else.
       } else {
         stack = stack>>1;
         b++;
       }
    }
    b=0;
    stack = step_colour_bresenham();
    // may produce steps for more than one extruder at once, but only one per extruder
  } while (true);
}