Screenshotting from a Strategy

[NinjaCustomer]

Would there be any problem if I don't use Dispatch.Invoke() while screenshotting?

I am using the code from this example created by NinjaTrader Support - Dave

https://ninjatrader.com/support/forum/forum/historical-beta-archive/version-8-beta/83572-screenshot-share?p=717302#post717302

or is there a built-in function now?

It works great except for the fact that some of my newly drawn elements don't appear and I think that is because it is using Invoke

[NinjaTrader_ChelseaB]

Hello NinjaCustomer,

Because the UI and NinjaScripts are on different threads, it is necessary to use the ChartControl.Dispatcher.InvokeAsync() to invoke into the UI thread to take a picture of the UI from the script without causing one or both threads to lock up.

Invoke() and BeginInvoke() can both cause thread lockups.

Below is a link to an example.
https://ninjatrader.com/support/foru...95#post1050595

Unfortunately, there is no built-in functionality for saving a screenshot from a script.

I will submit a feature request on your behalf for the development team to consider this.

[NinjaCustomer]

I can leave the State == State.Configure assignment as

Dispatcher.BeginInvoke(new Action(() => { chart = Window.GetWindow(ChartControl) as Chart; })); ? and just change to the ChartControl.Dispatcher.InvokeAsync() for the screenshotting?

[NinjaTrader_ChelseaB]

Hello NinjaCustomer,

Yes, BeginInvoke should always be InvokeAsync().

However, does the example I have provided you work as expected?
If so, I would recommend modeling your code after the working example.
If not, let me know and I will take a look to see if I am able to reproduce.

[NinjaCustomer]

Hi, the code that performs the actual screenshot looks the same like I have the code in my Strategy (taken from the Dave version I linked to) - so that works fine, on BeginInvoke - I was using it for the last 2 days without problems apart from what I mentioned about arrows not having been drawn on the chart yet. I have now changed to invoke async but I haven't had time to test that yet.

So I need to add this WPF Controls code ? or if I haven't had problems yet then I might not need it? I am only taking screenshots from a Strategy, not Indicator - don't know if that matters.

[NinjaTrader_ChelseaB]

Hello NinjaCustomer,

The wpf buttons added are to make it easy to take the screenshot when clicking the button, but are not required. This does make it easy to ensure that all the desired objects are being included with the screenshot.

If you are taking the screenshot after calling a draw method, you may want to wait until after the next render pass so the object is drawn first. (Like setting a flag in OnRender() to take the screenshot on the next tick in OBU/OMD)

[NinjaCustomer]

would OnRender() make a difference to what I normally do? I force refresh the chart first before saving the screenshot. My screenshotting is to save the chart state after entering or exiting a trade so that I can debug any problems later

[NinjaTrader_ChelseaB]

Hello NinjaCustomer,

Calling ForceRefresh() sets a flag that the chart should be rendered on the next render pass. It doesn't cause the chart to immediately re-render.
https://ninjatrader.com/support/help...rcerefresh.htm

Even if it did, if you are calling ForceRefresh() are you waiting until after the chart has been re-rendered before taking the screenshot?
Rendering happens asynchronously in another thread and takes a small amount of time.

[NinjaCustomer]

ok, how about this...

1. make a trade
2. draw the arrows
3. set a flag
4. have onrender check the flag
5. when set then call invokeasync from there to make the screenshot

?

[NinjaTrader_ChelseaB]

Hello NinjaCustomer,

My recommendation would be not to add any code to OnRender() that is not absolutely necessary.
OnRender() is called a lot, and you don't want any code in here that could cause delays.
I am still recommending what I recommend in post #6, that you set the flag in OnRender() and then take the screenshot on the next pass of OnBarUpdate or OnMarketData.

[NinjaCustomer]

ok got it...

1. set flag A after drawing arrows in OnBarUpdate() which is where I draw my arrows and call screenshot right now
2. OnRender: if flag A is set, set flag B
3. in OnMarketData check flag B and InvokeAsync if set

I assume OnMarketData happens at least as often as OnBarUpdate

[NinjaTrader_ChelseaB]

Hello NinjaCustomer,

Yes, OnMarketData triggers for every received market update (so updates more often than OnBarUpdate), but triggers immediately after OnBarUpdate.

[NinjaCustomer]

thanks, one more question here

so what exactly does the screenshot capture?

The current tab of the window?

or the current tab of the whole NT8 workspace?

[NinjaTrader_ChelseaB]

Hello NinjaCustomer,

The example I have provided you takes a picture of the chart tab contents.

Is this performing differently when you have tested it?

[NinjaCustomer]

it is taking a picture of the active tab, but since I was not using other windows (had them open but didn't switch focus to them - I was just switching between tabs of the same window) I am unsure if it takes a screenshot of the chart of active tab of the same window that the chart with the strategy is running in, or if it just takes a screenshot of the active tab of the focused window of the workspace, that is what I'm trying to clarify. Because if it is just the active tab of the strategy window then I can simply move the tab I like to switch to out to a separate window so I can view and still be confident that every time I take a screenshot it will be of the strategy chart because I would just leave that chart as the active tab of its window.

Hopefully I'm not being too confusing here.