mql5/Experts/_Architecture/Graphics/Screen.mqh

//+------------------------------------------------------------------+
//|                                                       Screen.mqh |
//|                                  Copyright 2025, MetaQuotes Ltd. |
//|                                             https://www.mql5.com |
//+------------------------------------------------------------------+
#property copyright "Copyright 2025, MetaQuotes Ltd."
#property link      "https://www.mql5.com"
#property version   "1.00"

#include <Collection/DynamicArraylist.mqh>
#include "ZoneObject.mqh"
#include "ScreenListener.mqh"
//+------------------------------------------------------------------+
//|                                                                  |
//+------------------------------------------------------------------+
class Screen
  {

private:
   long              m_chart_id;
   int               m_width, m_height;

   long              m_zoom;
   int               m_fontSize;
   long              m_min_zoom_to_keep_texts;
   bool              m_min_zoom_reached_already;

   datetime          m_from_time, m_to_time;
   double            m_min_price, m_max_price;

   CArrayList<ZoneObject*>* objects;


   void              UpdateViewBounds();
   void              OnZoomChanged();
   void              OnViewChanged();
   void              OnMinZoomReached();

   int               FindExist(ZoneObject* zoneObject)
     {
      for(int i = objects.Size() - 1; i >= 0; i--)
        {
         ZoneObject* z = objects.At(i);

         if(z.GetName() == zoneObject.GetName() && z.GetName() == zoneObject.GetName())
           {
            return i;
           }
        }
      return -1;

     }
   int               GetScaledFontSize(int baseSizePoints) const
     {
      return (int)MathMax(6.0, baseSizePoints - (m_zoom - 2));
     }

public:
                     Screen(): m_fontSize(12), m_chart_id(ChartID()) { objects = new CArrayList<ZoneObject*>(); UpdateViewBounds(); }
                    ~Screen() {delete objects;}

   void              SetMinZoomForTexts(long zoomLevel) { m_min_zoom_to_keep_texts = zoomLevel; }
   void              OnChartEvent(const int id, const long &lparam, const double &dparam, const string &sparam);
   void              AddLevel(ZoneObject* zoneObject);

   void              Render();
  };
//+------------------------------------------------------------------+
//|                                                                  |
//+------------------------------------------------------------------+
void Screen::OnChartEvent(const int id, const long &lparam, const double &dparam, const string &sparam)
  {
   if(id == CHARTEVENT_CHART_CHANGE)
     {

      UpdateViewBounds();
     }
  }
//+------------------------------------------------------------------+
//|                                                                  |
//+------------------------------------------------------------------+
void Screen::AddLevel(ZoneObject* zoneObject)
  {
   if(zoneObject.GetSymbol() != _Symbol)
     {
      Print("Error Adding Levels");
      return;
     }

   objects.Add(zoneObject);
   Render();

  }

//+------------------------------------------------------------------+
//|                                                                  |
//+------------------------------------------------------------------+
void Screen::Render()
  {
   UpdateViewBounds();
   bool boundsValid = (m_from_time < m_to_time && m_min_price < m_max_price);

   for(int i = objects.Size() - 1; i >= 0; i--)
     {
      objects.At(i).UpdateDraw(ChartGetInteger(m_chart_id, CHART_SCALE), m_from_time, m_to_time, m_min_price, m_max_price, m_min_zoom_to_keep_texts);
     }
  }
//+------------------------------------------------------------------+
//|                                                                  |
//+------------------------------------------------------------------+
void Screen::OnZoomChanged()
  {
   if(!m_min_zoom_reached_already)
     {
      for(int i = objects.Size() - 1; i >= 0; i--)
        {
         objects.At(i).SetFontSize(GetScaledFontSize(m_fontSize));
        }
     }
  }

//+------------------------------------------------------------------+
//|                                                                  |
//+------------------------------------------------------------------+
void Screen::OnViewChanged()
  {
   Render();
  }

//+------------------------------------------------------------------+
//|                                                                  |
//+------------------------------------------------------------------+
void Screen::OnMinZoomReached()
  {
   for(int i = objects.Size() - 1; i >= 0; i--)
     {
      objects.At(i).DeleteAllText();
     }
  }
//+------------------------------------------------------------------+
//| View bounds update                                               |
//+------------------------------------------------------------------+
void Screen::UpdateViewBounds()
  {
   long old_zoom = m_zoom;
   datetime old_from = m_from_time;
   datetime old_to = m_to_time;
   double old_minp = m_min_price;
   double old_maxp = m_max_price;

   m_width  = (int)ChartGetInteger(m_chart_id, CHART_WIDTH_IN_PIXELS);
   m_height = (int)ChartGetInteger(m_chart_id, CHART_HEIGHT_IN_PIXELS);
   m_zoom   = ChartGetInteger(m_chart_id, CHART_SCALE);

   int sub_window = 0;
   ChartXYToTimePrice(m_chart_id, 0, 0, sub_window, m_from_time, m_max_price);
   ChartXYToTimePrice(m_chart_id, m_width, m_height, sub_window, m_to_time, m_min_price);

   if(m_zoom != old_zoom)
     {
      OnZoomChanged();
      bool below_threshold = (m_zoom < m_min_zoom_to_keep_texts);

      if(below_threshold && !m_min_zoom_reached_already)
        {
         OnMinZoomReached();
         m_min_zoom_reached_already = true;

        }
      else
         if(!below_threshold)
           {
            m_min_zoom_reached_already = false;
            //  Render();
           }
     }

   if(m_from_time != old_from || m_to_time != old_to ||
      m_min_price != old_minp || m_max_price != old_maxp)
     {
      OnViewChanged();
     }

  }
//+------------------------------------------------------------------+