Discussion of article "Developing custom indicators using CCanvas class" - page 2

[Andrey Khatimlianskii]

fxsaber:

That's good news! What's the idea? Instead of a tick history, a custom time series?

No. Draw a histogram of tick rate next to the tick history.

So that, playing with the parameters, you can visually determine the periods of activity and, perhaps, find some patterns.

[Alexander Fedosov]

Dennis Kirichenko:

Good topic. Thanks to the author, will be making a tick indicator on canvas.....

I noticed this.

There is a private data member m_canvas_name, but the method that sets its value - Name() - is public. Imho, the encapsulation principle is violated. I will make this method private.

Maybe protected ? Because all the others inherit CCanvasBase. And then it will be impossible to use this method in them. Although I do not know, maybe you have changed something else in the general structure.

[Denis Kirichenko]

Alexander Fedosov:

Maybe protected ? Because all the others inherit CCanvasBase. And then you can't use this method in them. Although I don't know, maybe you have changed something else in the general structure.

So yes, protected.

Then here:

bool CCanvasBase::DeleteCanvas()
  {
   return(ObjectDelete(0,m_canvas_name)?true:false);
  }

//+------------------------------------------------------------------+
//| Custom indicator deinitialisation function |
//+------------------------------------------------------------------+
void OnDeinit(const int reason)
  {
   ind.Delete();
   ChartRedraw();
  }

Why so complicated in the indicator? Imho, it is necessary to clean up the canvas itself. I would add ChartRedraw() to the DeleteCanvas() method.

[Denis Kirichenko]

fxsaber:

When you have sketches, please send screenshots/video. I posted such an indicator myself, but it did not go to the people. Although I haven't found a better one. It's interesting to see other solutions on kanvas.

I'm making one for FORTS. I made it in the usual format, but in the Tester it works like hell when called from the EA body. Now I will transfer all the code to the EA...

[Alexander Fedosov]

Dennis Kirichenko:

Yeah, that's right.

Then here:

Why so complicated in the indicator? In my opinion, it is necessary to clean up the canvas itself. I would add ChartRedraw() to the DeleteCanvas() method.

Yes, this way there will be less unnecessary lines. We make the canvas neat and send the redraw there.

[Denis Kirichenko]

That's not really the way to do it:

//+------------------------------------------------------------------+
//|| Deletes a graphics resource|
//+------------------------------------------------------------------+
bool CCanvasBase::DeleteCanvas()
  {
   return(ObjectDelete(0,m_canvas_name)?true:false);
  }

Why a ternary operator? - When you can just do it:

//+------------------------------------------------------------------+
//|| Deletes a graphics resource|
//+------------------------------------------------------------------+
bool CCanvasBase::DeleteCanvas()
  {
   return ObjectDelete(0,m_canvas_name);
  }

I did it this way:

//+------------------------------------------------------------------+
//|| Deletes a graphics resource|
//+------------------------------------------------------------------+
bool CCanvasBase::DeleteCanvas()
  {
   if(ObjectFind(0,m_canvas_name)>-1)
      if(ObjectDelete(0,m_canvas_name))
        {
         ChartRedraw();
         return true;
        }
   return false;
  }

But canvas has its own method of deleting CCanvas::Destroy().

Why do we need to add something else?

[Denis Kirichenko]

I have a problem with vertical scaling.

I want to make a tick chart on RTS, where the maximum on the Y axis is 97784.0 and the minimum is 97756.0.

I do this in the code:

//--- update the chart
double min_y=NormalizeDouble(min_pr-0.2*diff,_Digits);
double max_y=NormalizeDouble(max_pr+0.2*diff,_Digits);
ticks_ind.YMin(min_y);
ticks_ind.YMax(max_y);
ticks_ind.SetArrayValue(prices);

I get this:

https://www.mql5.com/ru/charts/7227612/rts-9-17-m1-ao-otkritie-broker

The minimum is shown correctly, but then there is some whizzing.

Apparently, the CLineGraph::VerticalScale() method is not as fine-tuned as I think, or worse, as it should be.

[Anatoli Kazharski]

Dennis Kirichenko:

...

Try this class >>> CGraphic

Visualise it! Graphics library in MQL5 as an analogue of plot from R

Testing CGraphic - questions and suggestions

[Denis Kirichenko]

Anatoli Kazharski:

Try this class >>> CGraphic

Visualise it! Graphics library in MQL5 as an analogue of plot from R

Testing CGraphic - questions and suggestions

Anatoly, thanks for the tip, I will use it. It's a shame that the idea turns out to be unfriendly code...