Help needed with managing drawing objects

Hi all, I have been working through JoshM's tut on managing drawing objects as collections
https://www.tradingcode.net/multicharts ... ollection/

Good stuff.

But, I am looking for examples for the following use case:
I want to keep a list of rectangles (for instance, to highlight consolidations). I expect that the most recent rectangle will need to be updated if it borders on bar 0. Such that its starting date time remains the same, but if bar 0's conditions are still valid, the rectangle will continue to extend its "datetime 2" to bar 0 until the conditions no longer apply. Or I might want the upper and lower bounds of the rectangle to match a range's highs / lows.

What I don't understand:
What is the best way to manage this? Delete the most recent rectangle, and then create a new one with the conditions needed?

• If so, then how can I get the existing rectangle's datetimes and values? I can't find a way to extract those from the List object. Without those it's more complicated to create a new rectangle with the updated parameters.

Or is there a way to get the reference to the Rectangle Object and update it?

• Just as I could not find a way to extract the parameters from the existing rectangle in the List, I don't know how to grab a reference to the drawn object and then apply an update to its parameters.

I am sure there is a way! Can someone point me in the direction of the right example / article / etc?

Can you send me your previous code and 1-2 pictures of what exactly you want to achieve or what you are trying to achieve?

Otherwise she gave herself the answer. Simply update the "end points" of your rectangle chart points until it should no longer be updated according to your requirements. If you create your own (new) line for your lines, you don't actually need to delete it, but you could update it.
For example, you could not write the last points in the list, but in a variable object and only add them to the list when you no longer need the last point.

If you can't call up the points of the rectangle, simply create a list with the chart points, then you can access the individual points at any time... take a look at the code snippet above, for example I also wrote a method for this and below you can see how you could, for example, call up the price for a specific chart point

Otherwise, Josh shows how it works on his website. You could simply iterate through the list of the drawing with a for loop and then, for example, delete the last entry and then insert a new point.

Maybe this is also a problem for you: [RecoverDrawings(false)] --- just google it or try with true/false.

Hi HellGhost - not quite what I wanted to do, but it got me a little closer. Thank you for the inspiration. I still have an error that I cannot get past.

Noting that you made a list of ChartPoints, I made my list of IRectangleObjects, and that allowed me to access the Properties of the rectangles (ie: Begin, End, etc)

Here's my toy code that shows what I want to do: The error that occurs when I try to assign a new chartpoint to an existing End property is this: "System.ApplicationException: This was never displayed!"

I also tried accessing the individual parameters of the chartpoint: But that was no more successful. All of these properties should be both Get and Set according to the documentation: So, it seems that the methods and properties are available to use, but something about my syntax is preventing me from updating a pre-existing rectangle. Of course, I could: But, if I can update the existing rectangle, that should be the easier, better option. Can it be done?

Hi HellGhost - not quite what I wanted to do, but it got me a little closer. Thank you for the inspiration. I still have an error that I cannot get past.

Noting that you made a list of ChartPoints, I made my list of IRectangleObjects, and that allowed me to access the Properties of the rectangles (ie: Begin, End, etc)

Here's my toy code that shows what I want to do:

Code: Select all

using System; using System.Drawing; using System.Linq; using PowerLanguage.Function; using System.Collections.Generic; // Added for List namespace PowerLanguage.Indicator { [SameAsSymbol(true)] public class _TEST_ChartObjects_Stacks : IndicatorObject { public _TEST_ChartObjects_Stacks(object _ctx) : base(_ctx) { } private List<IRectangleObject> myDrawings; protected override void Create() { Output.Clear(); } protected override void StartCalc() { myDrawings = new List<IRectangleObject>(); } protected override void CalcBar() { if (Bars.FullSymbolData.Current == Bars.FullSymbolData.Count - 1) { myDrawings.Add(DrwRectangle.Create(new ChartPoint(Bars.Time[55], Bars.Low[55]), new ChartPoint(Bars.Time[45], Bars.High[45]))); if(myDrawings.Count > 0){ IRectangleObject robj = myDrawings.Last<IRectangleObject>(); // This writes to Output successfully Output.WriteLine("End point {0}", robj.End.ToString()); ChartPoint cp = new ChartPoint(Bars.Time[2], Bars.High[2]); robj.End = cp; // This fails with "System.ApplicationException: This was never displayed!" Output.WriteLine("End point {0}", robj.End.ToString()); } } } } }

The error that occurs when I try to assign a new chartpoint to an existing End property is this:Rectangle error.JPG
"System.ApplicationException: This was never displayed!"

I also tried accessing the individual parameters of the chartpoint:

Code: Select all

robj.End.Time = Bars.Time[2]; robj.End.Price = Bars.High[2];

But that was no more successful. All of these properties should be both Get and Set according to the documentation:chartpointtime.JPGchartpointend.JPG

So, it seems that the methods and properties are available to use, but something about my syntax is preventing me from updating a pre-existing rectangle. Of course, I could:

Code: Select all

<pseudocode> Capture the Begin point of the last rectangle to a ChartPoint variable Delete the last rectangle Add a new Rectangle using the old Begin chartpoint and an updated End chartpoint </pseudocode>

But, if I can update the existing rectangle, that should be the easier, better option. Can it be done?

So, I didn't solve the problem, but I think I found the issue. I'm making uneducated guess that lack of Date value in cp is causing the problem.

Try to either draw rectangle using time, if it won't help then delete the rectangle and create a new one. Please report back what you found out.

BD, thank you for joining the conversation.

Upon seeing your post, I did a similar test to print out the chartpoints. I am not getting the erroneous dates, I see correct datetimes. I changed the bar numbers a few times to be sure. I don't think that is the issue.

Although, while knocking my way through the code a bit more, I found something out. DrwRectangles need a NEW ChartPoint declared when they are created. So, even if I had just declared a CP to a new variable and tried to use that, it would not work. But, even with this, I tried updating the end coordinates of a rectangle with a new chartpoint and that would not do it.

So, I can get it to work with the code below. I gave up and resorted to deleting the last rectangle and replacing, and re-introduced the mouseclick controls to demonstrate the updating. While the code is a bit over-cooked, I can clean it up and use it. I learned a bit more about C# along the way. I hope it helps someone else.

MultiCharts team - both the IRectangleObject and ChartPoint show that their Public Instance properties are both Get/Set or Read/Write. They are not shown as static. What is the proper syntax for updating them once they are created?