Events in Urho3D

I have little trouble understand Events in Urho.
When can I use SendEvent and which type of event I have to use?
Another question is for VarianMap, which event should I use for detect the event?

for example I use SendEvent inside HandleUpdate (from tutorial sample project) with this code:

VariantMap eData;
if (input->GetKeyPress(KEY_O))
			{
				eData[Update::P_TIMESTEP] = "hmm"; 
				SEND_EEVENT = true;
			}
if (SEND_EEVENT == true)
		{
			SEND_EEVENT = false;
			SendEvent(E_UPDATE, eData);
		}

but after this SendEvent() urho goes in to infinite loop and then crash. when I change eData in to eventData from function arguments, and don’t send data, then it is working and I can read “hmm” from eventData. Then I start thinking, maybe I should use SendEvent outside HandleUpdate function?

E_UPDATE is one of the core events in the engine so you shouldn’t call it manually. Create your own events if you want to add additional logic.

VariantMap myData = GetEventDataMap();
myData["SomeText"] = "Hello, world!";
myData["Number"] = 1;
SendEvent("MyCustomEvent", myData);

and add a listener to it

SubscribeToEvent("MyCustomEvent", URHO3D_HANDLER(MyClass, HandleMyCustomEvent));

...

void MyClass::HandleMyCustomEvent(StringHash eventType, VariantMap& eventData)
{
    String text = eventData["SomeText"].GetString();
    int number = eventData["Number"].GetInt();
}

When you send an event in the application, all the objects which subscribed to it will receive it immediately. When you called the E_UPDATE event your application probably got stuck in the HandleUpdate method because it was called over and over again without letting the engine to run the next frame.

Thanks, it is now clear to me.

One thing, you wrote:
VariantMap myData = GetEventDataMap();
is the GetEventDataMap necessary? I create only VariantMap without GetEventDataMap, and it is working. Or for what is good set VariantMap = GetEventDataMap ?

Thats one of the optimizations to avoid creating the VariantMap on the fly which should give a performance boost, as far as I know. Not sure how much performance it gives tho.

Thanks. Urho3D Events Documentation should be extented to this informations. I think they are helpfull.

Here are some references…
Events: https://urho3d.github.io/documentation/HEAD/_events.html
GetEventDataMap(): https://urho3d.github.io/documentation/HEAD/_main_loop.html

Do be aware that the VariantMaps returned by GetEventDataMap() are not cleared to an empty state (unless that’s changed recently) so they can contain old/invalid fields if you don’t fully set all of the Event’s parameters - not a big deal because you usually will be doing that.

Edit: the above is entirely incorrect.

The method clears the VariantMap object first before reusing it.

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Oh, then I’m misremembering it. Thanks for the correction.