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MSFS20 Trying to figure out the best way to communicate between on-screen in-game panels and SimConnect

H

HornetJockey

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83
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us-newyork
I have an in-game panel I created (basically a HTML/JS panel, same as the top menu panels like Weather, Camera, etc.), and I'd like to be able to send an event to SimConnect (which will trap it and act on it) when, for instance, I toggle a switch or press a button. Right now I am using LVARS but I find them unreliable - sometimes the LVAR is not passed through to the SimConnect client.

Is there a better way?
 
I'm not sure if it'll work (I've never tried this in particular), but you might be able to use SimConnect_MapClientEventToSimEvent if the only thing you want to communicate is whether something happened (using the Custom.Event or #0xnnnn stuff in the EventName parameter)? (I'm not sure if Coherent will let you send those sorts of custom events on the JavaScript side though.)

Otherwise, your best bet is probably the Communication API (though if you have an external/out-of-process SimConnect client, that's only an option in MSFS 2024 with the new SimConnect Communication API as of Sim Update 5 -- but if you have a WASM module, you can use the Communication API regardless; the Communication API is available through WASM in both MSFS 2020 and MSFS 2024).
 
ollyau said:
I'm not sure if it'll work (I've never tried this in particular), but you might be able to use SimConnect_MapClientEventToSimEvent if the only thing you want to communicate is whether something happened (using the Custom.Event or #0xnnnn stuff in the EventName parameter)? (I'm not sure if Coherent will let you send those sorts of custom events on the JavaScript side though.)

Otherwise, your best bet is probably the Communication API (though if you have an external/out-of-process SimConnect client, that's only an option in MSFS 2024 with the new SimConnect Communication API as of Sim Update 5 -- but if you have a WASM module, you can use the Communication API regardless; the Communication API is available through WASM in both MSFS 2020 and MSFS 2024).
Click to expand...
Hey, THANKS for taking time to answer, I appreciate it! I was Googling it in the last hour or so and it spewed out something similar that I may try (tomorrow, very sleepy now), but this is what AI dished out:

On JS side:

Code: 
// Example: Trigger a custom event without a parameter (e.g., Increase Heading)
SimVar.SetSimVarValue("K:A32NX.FCU_HDG_INC", "number", 0);
// Example: Trigger an event requiring a specific value/axis state
SimVar.SetSimVarValue("K:SOME_CUSTOM_EVENT", "number", 1);


And on C++ side:

Code: 
#include <windows.h>
#include "SimConnect.h"

// Define your custom event enum ID
enum EVENT_ID {
    EVENT_CUSTOM_K_VAR
};

// Map the custom event string to your internal ID
SimConnect_MapClientEventToSimEvent(hSimConnect, EVENT_CUSTOM_K_VAR, "A32NX.FCU_HDG_INC");

// Transmit the event (dwData represents the value/state)
DWORD dwData = 0; // Value parameter, if applicable
SimConnect_TransmitClientEvent(
    hSimConnect,
    0, // Object ID (0 for user aircraft)
    EVENT_CUSTOM_K_VAR,
    dwData,
    SIMCONNECT_EVENT_FLAG_GROUPID_IS_PRIORITY,
    SIMCONNECT_GROUP_PRIORITY_HIGHEST
);

I'll report how this works out.
 
For what it's worth (just in case it isn't clear), if you're dealing with key events and want to listen on the SimConnect side, you'll still need to use SimConnect_AddClientEventToNotificationGroup (and possibly SimConnect_SetNotificationGroupPriority as well) at some point -- it's worth looking at the SDK samples for reference (LLMs only ever create things that plausibly sound like answers, but there's no guarantee that it'll necessarily be an actual answer, especially for niche stuff like SimConnect).
 
ollyau said:
For what it's worth (just in case it isn't clear), if you're dealing with key events and want to listen on the SimConnect side, you'll still need to use SimConnect_AddClientEventToNotificationGroup (and possibly SimConnect_SetNotificationGroupPriority as well) at some point -- it's worth looking at the SDK samples for reference (LLMs only ever create things that plausibly sound like answers, but there's no guarantee that it'll necessarily be an actual answer, especially for niche stuff like SimConnect).
Click to expand...
Hey, thanks! The problem is, there ARE no SDK samples for this particular case, unless I am missing something...

Ok, I implemented my code, but no dice :(

Here is the code, first, setup on SimConnect/C++ side:
Code: 
hr = SimConnect_MapClientEventToSimEvent(hSimConnect, EVENT_CUSTOM_K_VAR, "CUSTOM_K_VAR");
hr = SimConnect_AddClientEventToNotificationGroup(hSimConnect, GROUP_KEYS, EVENT_CUSTOM_K_VAR);
hr = SimConnect_SetNotificationGroupPriority(hSimConnect, GROUP_KEYS, SIMCONNECT_GROUP_PRIORITY_HIGHEST);

And then, in JS, where the event is triggered:
Code: 
onToggle_MY_TOGGLE() {
        if (this.m_toggle_MY_TOGGLE.toggled) {
            SimVar.SetSimVarValue("K:CUSTOM_K_VAR", "number", 0);
        }
    }
And finally, in the event loop, where the event should be trapped:
Code: 
case SIMCONNECT_RECV_ID_EVENT:
            {
                SIMCONNECT_RECV_EVENT *evt = (SIMCONNECT_RECV_EVENT*)pData;
                switch(evt->uEventID)
                {
                    case EVENT_CUSTOM_K_VAR:
                        printf("EVENT_CUSTOM_K_VAR WORKING\n");
                        break;
No event is being trapped :rolleyes:
 
I'd recommend trying what the documentation says about custom events (you can't just pick whatever you want for the EventName parameter; it needs to follow the convention as described in the SDK):

2024: https://docs.flightsimulator.com/ms..._Data/SimConnect_MapClientEventToSimEvent.htm
2020: https://docs.flightsimulator.com/ht..._Data/SimConnect_MapClientEventToSimEvent.htm
FSX/ESP: https://learn.microsoft.com/en-us/p...=msdn.10)#simconnect_mapclienteventtosimevent

Refer to the Event IDs document for a list of event names (listed under String Name). If the event name includes one or more periods (such as "Custom.Event" in the example below) then they are custom events specified by the client, and will only be recognized by another client (and not ESP) that has been coded to receive such events. No ESP events include periods. If no entry is made for this parameter, the event is private to the client.

Alternatively enter a decimal number in the format "#nnnn" or a hex number in the format "#0xnnnn", where these numbers are in the range THIRD_PARTY_EVENT_ID_MIN and THIRD_PARTY_EVENT_ID_MAX, in order to receive events from third-party add-ons to ESP.
Click to expand...

Particularly, look at the SendEventA, SendEventB, SendEventC, or SetData samples. I'm still not sure if you'll be able to send events from Coherent, but that should show you how custom events work on the SimConnect side.
 
HornetJockey said:
Hey, thanks! The problem is, there ARE no SDK samples for this particular case, unless I am missing something...

Ok, I implemented my code, but no dice :(

Here is the code, first, setup on SimConnect/C++ side:
Code: 
hr = SimConnect_MapClientEventToSimEvent(hSimConnect, EVENT_CUSTOM_K_VAR, "CUSTOM_K_VAR");
hr = SimConnect_AddClientEventToNotificationGroup(hSimConnect, GROUP_KEYS, EVENT_CUSTOM_K_VAR);
hr = SimConnect_SetNotificationGroupPriority(hSimConnect, GROUP_KEYS, SIMCONNECT_GROUP_PRIORITY_HIGHEST);

And then, in JS, where the event is triggered:
Code: 
onToggle_MY_TOGGLE() {
        if (this.m_toggle_MY_TOGGLE.toggled) {
            SimVar.SetSimVarValue("K:CUSTOM_K_VAR", "number", 0);
        }
    }
And finally, in the event loop, where the event should be trapped:
Code: 
case SIMCONNECT_RECV_ID_EVENT:
            {
                SIMCONNECT_RECV_EVENT *evt = (SIMCONNECT_RECV_EVENT*)pData;
                switch(evt->uEventID)
                {
                    case EVENT_CUSTOM_K_VAR:
                        printf("EVENT_CUSTOM_K_VAR WORKING\n");
                        break;
No event is being trapped :rolleyes:
Click to expand...
Hi,

You are very close... all you need to do is rename your custom var. It really does need a "." in the name - all you need to do is insert "something." in front of your variable (in our case below, "MY."). So:
Code: 
hr = SimConnect_MapClientEventToSimEvent(hSimConnect, EVENT_CUSTOM_K_VAR, "MY.CUSTOM_K_VAR");
hr = SimConnect_AddClientEventToNotificationGroup(hSimConnect, GROUP_KEYS, EVENT_CUSTOM_K_VAR);
hr = SimConnect_SetNotificationGroupPriority(hSimConnect, GROUP_KEYS, SIMCONNECT_GROUP_PRIORITY_HIGHEST);

Then:
Code: 
onToggle_MY_TOGGLE() {
        if (this.m_toggle_MY_TOGGLE.toggled) {
            SimVar.SetSimVarValue("K:MY.CUSTOM_K_VAR", "number", 0);
        }
    }
... and your event loop should trap that.

You can even send parameters (data) in JS, and that will be picked up in SimConnect:
Code: 
onToggle_MY_TOGGLE() {
        if (this.m_toggle_MY_TOGGLE.toggled) {
            SimVar.SetSimVarValue("K:MY.CUSTOM_K_VAR", "number", 1);
        } else
       {
            SimVar.SetSimVarValue("K:MY.CUSTOM_K_VAR", "number", 0);
        }
    }

And trapping it:
Code: 
case SIMCONNECT_RECV_ID_EVENT:
            {
                SIMCONNECT_RECV_EVENT *evt = (SIMCONNECT_RECV_EVENT*)pData;
                switch(evt->uEventID)
                {
                    case EVENT_CUSTOM_K_VAR:
                        TB_PRINTF("EVENT_CUSTOM_K_VAR WORKING: %d\n", (int)evt->dwData);
                        break;

And now you are getting the data passed in JS! "MY." can of course be anything, usually devs use it to designate company and product, as in "PMDG737.CUSTOM_K_VAR" so that it is not mixed up with other client's events.
 
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