https://github.com/BelledonneCommunications/liblinphone/blob/59d99bd981afe9d1748bf7d827deb64cca39beb3/coreapi/vtables.c

void linphone_core_notify_call_state_changed(LinphoneCore *lc, LinphoneCall *call, LinphoneCallState cstate, const char *message){

L_GET_PRIVATE_FROM_C_OBJECT(lc)->notifyCallStateChanged(call, cstate, message); <<----------------------------- notifyCallStateChanged 

NOTIFY_IF_EXIST(call_state_changed, lc,call,cstate,message);

cleanup_dead_vtable_refs(lc);

}

https://github.com/BelledonneCommunications/liblinphone/blob/59d99bd981afe9d1748bf7d827deb64cca39beb3/src/core/core.cpp

void CorePrivate::registerListener (CoreListener *listener) {

listeners.push_back(listener);

}

void CorePrivate::unregisterListener (CoreListener *listener) {

listeners.remove(listener);

}

void CorePrivate::notifyCallStateChanged (LinphoneCall *call, LinphoneCallState state, const string &message) {

auto listenersCopy = listeners; // Allow removal of a listener in its own call

for (const auto &listener : listenersCopy)

listener->onCallStateChanged(call, state, message); <<-------------------- onCallStateChanged

}

https://github.com/BelledonneCommunications/liblinphone/blob/6461d23dd5d9bbb03926ab8935473087f526469a/src/conference/session/call-session.cpp

void CallSessionPrivate::onCallStateChanged (LinphoneCall *call, LinphoneCallState state, const std::string &message) {

this->executePendingActions();

}

onCallStateChanged CallManager.swift

func onCallStateChanged(core: Core, call: Call, state cstate: Call.State, message: String) {

let callLog = call.callLog

let callId = callLog?.callId

if (cstate == .PushIncomingReceived) {

displayIncomingCall(call: call, handle: "Calling", hasVideo: false, callId: callId!, displayName: "Calling") <<--------- displayIncomingCall    

displayIncomingCall    CallManager.swift

func displayIncomingCall(call:Call?, handle: String, hasVideo: Bool, callId: String, displayName:String) {

let uuid = UUID()

let callInfo = CallInfo.newIncomingCallInfo(callId: callId)

providerDelegate.callInfos.updateValue(callInfo, forKey: uuid)

providerDelegate.uuids.updateValue(uuid, forKey: callId)

providerDelegate.reportIncomingCall(call:call, uuid: uuid, handle: handle, hasVideo: hasVideo, displayName: displayName) <<------ reportIncomingCall 

}

https://github.com/BelledonneCommunications/linphone-iphone/blob/524d4299602d886e0ec72270623993a45baa98f6/Classes/Swift/ProviderDelegate.swift

reportIncomingCall 

func reportIncomingCall(call:Call?, uuid: UUID, handle: String, hasVideo: Bool, displayName:String) {

let update = CXCallUpdate()

update.remoteHandle = CXHandle(type:.generic, value: handle)

update.hasVideo = hasVideo

update.localizedCallerName = displayName

let callInfo = callInfos[uuid]

let callId = callInfo?.callId

provider.reportNewIncomingCall(with: uuid, update: update) { error in  <<----- reportNewIncomingCall <<---------- from system

if error == nil {