Custom Indicator (Separate Window) AUTO-SCALE LIMIT

I have wanted to stop my indicator auto-scaling on the M1 time-scale as the result is more difficult to read.

The ...

#property indicator_maximum 5.0

is no good as it just scales the top of the window to that fixed value rather than using it as a minimum limit of the top of the window (which is what I want).

To be clear, if my indicator is in the range of +2 to -2 I want the window to be say +5 to -10. If the indicator value becomes -9 to -12 within the visible range I want the window scale to now be +5 to -12. In other words I am setting a limit below which the upper and lower values are not allowed to auto-scale. There does not seem to be any direct method to do this within MT4 so the task is to perform the function with the least amount of difficulty.

I have used an extra indicator buffer to perform this task, which seems pretty wasteful but it is the best I could think of. Now this buffer contains no useful information so I don’t want to see it. Obviously using EMPTY_VALUE for most of it is the answer. However all the values can’t be empty or it won’t prevent the graph auto-scaling.

I have defined two values ...

extern double indicatorHigh =   5.0;
extern double indicatorLow  = -10.0;

which are my auto-scale limits. I need at least one of each of these visibly drawn on the chart in order to be effective. Of course I don’t want to see them! So I have set that buffer colour as Black since my charts are on a Black background. I don’t see any programmatic way of either

a) reading the chart background colour

b) programmatically setting the indicator colour at run-time (ie not using the start-up colour selector)

There is another important point. The indicators seem to have a built-in Z-ordering so that indicator 1 is at the back of the display. Therefore you need to use indicator 1 for the scaling so that the real indicators over-write it.

And here is the final code snippet ...

   int limit = Bars - counted_bars;
             
   for(int n=limit; n>=0; n--){
                           
      SCALE[n] = EMPTY_VALUE;  // my dummy indicator which limits the autoscaling
      // put the real indicator work here
   }
   
   SCALE[1] = indicatorHigh;
   SCALE[0] = indicatorLow;

EDIT: This code is not quite right. If you turn off auto-scroll and look back in history the auto-scale limit fails since the limit points are at bar[0] and bar[1] which are not visible.

   SCALE[WindowFirstVisibleBar()]   = indicatorHigh;
   SCALE[WindowFirstVisibleBar()-1] = indicatorLow;

The above works better but is still not quite right as you have to wait for a new tick before the auto-scale limit works, which again is just not quite right. So here is my latest (working) version.

   for( int n=Bars-counted_bars; n>=0; n-- ){
                      
      // do the real indicator work in here
      
      if( n % 50 == 0 )
         SCALE[n] = indicatorHigh;
      else if( n % 50 == 1)
         SCALE[n] = indicatorLow;
      else
         SCALE[n] = EMPTY_VALUE;
   }