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Files
maszyna/widgets/multiplayer_lobby.cpp
Hirek193 9dc78a65dc multiplayer: stream the authoritative state, and let a client walk into a cab
First live test showed three things wrong at once.

A client could not take a vehicle. Walking up to a locomotive and pressing the
enter-vehicle key posts entervehicle, which stage 4 classed as a world-wide
command and refused outright ("reserved for the session host"), so the client
never got a cab and every later control command died locally for want of one.
Walking into a cab is a request for a seat, not a world command: the authority
now turns it into a crew claim, for the host through the same path as for a
remote peer, and answers it the way the lobby button is answered.

Nothing but commands was ever replicated. The server sent dt and the commands
it ran, and the client simulated the rest for itself - so a pantograph the host
raised before the client joined, the contents of the memory cells the signalling
reads, brake pressures and switch positions simply never crossed the wire. The
server now streams the authoritative state a few times a second: whatever has
changed since the last one, and the whole of it every so often so a peer heals
from anything it missed. The snapshot carries the vehicle's inputs - line
breaker, battery, converter and compressor permits, pantograph valves, cab,
lights, doors - and lets the receiving peer derive the rest, plus the memory
cells and the switches.

Desync detection demanded that two state digests be equal, on a design where
the client deliberately runs its own physics. They never can be, so it reported
a desync permanently and asked for a resync every five seconds forever, which
fixed nothing because the next step disagreed again. The digest is a log line
now; what is measured instead is how far out of place the routine correction
found us, and a full resync is only asked for when even that is not catching up.

Also: a consist is put back on the rails as a whole or not at all. Correcting
one vehicle while its neighbour stayed put is what was stretching couplers
until they tore - the last test moved six vehicles out of eight, every time.

And the lobby window collapsed to nothing, because its size_max was left at the
-1 default while size_min was set, so imgui was handed a maximum smaller than
the minimum.
2026-09-06 22:19:28 +00:00

159 lines
4.5 KiB
C++

/*
This Source Code Form is subject to the
terms of the Mozilla Public License, v.
2.0. If a copy of the MPL was not
distributed with this file, You can
obtain one at
http://mozilla.org/MPL/2.0/.
*/
#include "stdafx.h"
#include "widgets/multiplayer_lobby.h"
#include "application/application.h"
#include "network/entities.h"
#include "network/session.h"
#include "simulation/simulation.h"
#include "utilities/Globals.h"
#include "utilities/translation.h"
#include "utilities/utilities.h"
#include "vehicle/Driver.h"
#include "vehicle/DynObj.h"
#include "vehicle/Train.h"
ui::multiplayer_lobby_panel::multiplayer_lobby_panel()
: ui_panel(STR_C("Multiplayer lobby"), false)
{
// both bounds have to be set: ui_panel feeds them straight to imgui, and a maximum
// left at its -1 default is smaller than the minimum, which collapses the window
size_min = {560, 320};
size_max = {1920, 1080};
}
std::string ui::multiplayer_lobby_panel::describe_crew(network::NetworkEntityId const Entity) const
{
auto const crew = network::Crews.crew_of(Entity);
if (crew.empty())
return std::string();
std::string description;
for (network::PeerId const peer : crew)
{
if (!description.empty())
description += ", ";
if (peer == Global.network_peer_id)
description += STR("you");
else if (peer == network::PEER_HOST)
description += STR("host");
else
description += STR("player") + " " + std::to_string(peer);
}
return description;
}
void ui::multiplayer_lobby_panel::render_contents()
{
bool const host{Application.is_server()};
bool const client{Application.is_client()};
if (!host && !client)
{
ImGui::TextUnformatted(STR_C("This is not a multiplayer session."));
return;
}
ImGui::Text("%s: %s, peer %u", STR_C("Session"), host ? (client ? "host + client" : "host") : "client", Global.network_peer_id);
if (!Global.SceneryFile.empty())
ImGui::TextDisabled("%s", Global.SceneryFile.c_str());
if (!Global.network_lobby_message.empty())
ImGui::TextColored(ImVec4(1.0f, 0.6f, 0.3f, 1.0f), "%s", Global.network_lobby_message.c_str());
ImGui::Separator();
auto const &entries = network::Entities.entries();
if (entries.empty())
{
ImGui::TextUnformatted(client ? STR_C("Waiting for the vehicle list from the server...") : STR_C("This scenario has no vehicles anybody could drive."));
return;
}
network::NetworkEntityId const ownvehicle{network::Crews.vehicle_of(Global.network_peer_id)};
float const scale = std::max(1.0f, Global.ui_scale);
float const crewwidth = 60.0f * scale;
float const statewidth = 150.0f * scale;
float const actionwidth = 110.0f * scale;
ImGui::Columns(4, "mp_vehicles", false);
ImGui::SetColumnWidth(0, std::max(120.0f * scale, ImGui::GetWindowWidth() - crewwidth - statewidth - actionwidth - 30.0f * scale));
ImGui::SetColumnWidth(1, crewwidth);
ImGui::SetColumnWidth(2, statewidth);
ImGui::SetColumnWidth(3, actionwidth);
ImGui::TextDisabled("%s", STR_C("Vehicle"));
ImGui::NextColumn();
ImGui::TextDisabled("%s", STR_C("Crew"));
ImGui::NextColumn();
ImGui::TextDisabled("%s", STR_C("On board"));
ImGui::NextColumn();
ImGui::NextColumn();
ImGui::Separator();
for (auto const &entry : entries)
{
ImGui::PushID(static_cast<int>(entry.id));
ImGui::TextUnformatted(entry.name.c_str());
ImGui::NextColumn();
ImGui::Text("%u/%u", (unsigned)entry.crew_count, (unsigned)entry.crew_capacity);
ImGui::NextColumn();
std::string const crew{describe_crew(entry.id)};
if (!crew.empty())
ImGui::TextUnformatted(crew.c_str());
else
ImGui::TextDisabled("%s", entry.ai_active ? STR_C("AI") : STR_C("free"));
ImGui::NextColumn();
if (entry.id == ownvehicle)
{
if (ImGui::Button(STR_C("Leave")))
Application.request_vehicle_leave(entry.id);
}
else if (entry.claimable)
{
// a vehicle somebody else is already working on can still be joined, that is
// what the crew capacity is for
if (ImGui::Button(entry.crew_count > 0 ? STR_C("Join crew") : STR_C("Enter")))
claim(entry.id, ownvehicle);
}
else
{
ImGui::TextDisabled("%s", STR_C("full"));
}
ImGui::NextColumn();
ImGui::PopID();
}
ImGui::Columns(1);
ImGui::Separator();
ImGui::TextDisabled("%s", STR_C("You can also walk up to a vehicle and use the enter-vehicle key."));
}
void ui::multiplayer_lobby_panel::claim(network::NetworkEntityId const Entity, network::NetworkEntityId const Current)
{
if (Current != network::ENTITY_NONE)
{
// one person cannot work two vehicles at once
Application.request_vehicle_leave(Current);
}
Application.request_vehicle_claim(Entity);
}