sacred_k/src/mods/monitor.cpp

// Preferred monitor (request of 2026-10-25): a setting in the graphics options
// picks the monitor the game starts on; with none set, or the preferred one
// not connected, the system's main monitor.
//
// The game window and its render size are decided when the display mode is
// set at startup (borderless.cpp, widescreen.cpp ApplyRenderSize): both ask
// GameMonitorRect. A change applies at the next start.
//
// Monitors are told apart by their device path (DisplayConfigGetDeviceInfo,
// target name: "\\?\DISPLAY#GSM5B7F#..."), which survives restarts, monitor
// order changes and other ports' changes, unlike the GDI names \\.\DISPLAYn.
//
// sacredK.ini:
//   [display]
//   Monitor=<device path>   ; empty: the main monitor

#include "mods/monitor.h"

#include <algorithm>

#include "re/config.h"
#include "re/log.h"

namespace mods::monitor {
namespace {

constexpr const char* kSection = "display";
constexpr const char* kKey = "Monitor";

std::string Utf8(const wchar_t* text) {
    const int size = WideCharToMultiByte(CP_UTF8, 0, text, -1, nullptr, 0, nullptr, nullptr);
    if (size <= 1) {
        return {};
    }
    std::string result(static_cast<size_t>(size - 1), '\0');
    WideCharToMultiByte(CP_UTF8, 0, text, -1, result.data(), size, nullptr, nullptr);
    return result;
}

struct Target {
    std::wstring gdiName;  // \\.\DISPLAYn of the source showing it
    std::string id;
    std::wstring name;
};

// The active display paths: which monitor shows which GDI display.
std::vector<Target> Targets() {
    UINT32 pathCount = 0;
    UINT32 modeCount = 0;
    std::vector<DISPLAYCONFIG_PATH_INFO> paths;
    std::vector<DISPLAYCONFIG_MODE_INFO> modes;
    LONG result;
    do {
        if (GetDisplayConfigBufferSizes(QDC_ONLY_ACTIVE_PATHS, &pathCount, &modeCount) != ERROR_SUCCESS) {
            return {};
        }
        paths.resize(pathCount);
        modes.resize(modeCount);
        result = QueryDisplayConfig(QDC_ONLY_ACTIVE_PATHS, &pathCount, paths.data(), &modeCount, modes.data(),
                                    nullptr);
    } while (result == ERROR_INSUFFICIENT_BUFFER);
    if (result != ERROR_SUCCESS) {
        return {};
    }
    paths.resize(pathCount);
    std::vector<Target> targets;
    for (const DISPLAYCONFIG_PATH_INFO& path : paths) {
        DISPLAYCONFIG_SOURCE_DEVICE_NAME source = {};
        source.header.type = DISPLAYCONFIG_DEVICE_INFO_GET_SOURCE_NAME;
        source.header.size = sizeof(source);
        source.header.adapterId = path.sourceInfo.adapterId;
        source.header.id = path.sourceInfo.id;
        DISPLAYCONFIG_TARGET_DEVICE_NAME target = {};
        target.header.type = DISPLAYCONFIG_DEVICE_INFO_GET_TARGET_NAME;
        target.header.size = sizeof(target);
        target.header.adapterId = path.targetInfo.adapterId;
        target.header.id = path.targetInfo.id;
        if (DisplayConfigGetDeviceInfo(&source.header) != ERROR_SUCCESS ||
            DisplayConfigGetDeviceInfo(&target.header) != ERROR_SUCCESS) {
            continue;
        }
        targets.push_back({source.viewGdiDeviceName, Utf8(target.monitorDevicePath), target.monitorFriendlyDeviceName});
    }
    return targets;
}

BOOL CALLBACK AddMonitor(HMONITOR handle, HDC, LPRECT, LPARAM data) {
    auto* gdi = reinterpret_cast<std::vector<MONITORINFOEXW>*>(data);
    MONITORINFOEXW info = {};
    info.cbSize = sizeof(info);
    if (GetMonitorInfoW(handle, &info)) {
        gdi->push_back(info);
    }
    return TRUE;
}

}  // namespace

std::vector<Monitor> List() {
    std::vector<MONITORINFOEXW> gdi;
    EnumDisplayMonitors(nullptr, nullptr, &AddMonitor, reinterpret_cast<LPARAM>(&gdi));
    const std::vector<Target> targets = Targets();
    std::vector<Monitor> monitors;
    for (const MONITORINFOEXW& info : gdi) {
        Monitor monitor{"", L"", info.rcMonitor, (info.dwFlags & MONITORINFOF_PRIMARY) != 0};
        for (const Target& target : targets) {
            if (target.gdiName == info.szDevice) {  // mirrored displays: the first monitor
                monitor.id = target.id;
                monitor.name = target.name;
                break;
            }
        }
        if (monitor.id.empty()) {
            monitor.id = Utf8(info.szDevice);  // no display config (remote desktop, ...)
        }
        if (monitor.name.empty()) {
            monitor.name = L"Monitor " + std::to_wstring(monitors.size() + 1);
        }
        monitors.push_back(monitor);
    }
    std::stable_sort(monitors.begin(), monitors.end(),
                     [](const Monitor& a, const Monitor& b) { return a.primary && !b.primary; });
    return monitors;
}

std::string PreferredId() {
    return re::ConfigString(kSection, kKey, "");
}

void SetPreferredId(const std::string& id) {
    re::SetConfigString(kSection, kKey, id.c_str());
}

RECT GameMonitorRect() {
    const std::vector<Monitor> monitors = List();
    const std::string preferred = PreferredId();
    const Monitor* chosen = nullptr;
    for (const Monitor& monitor : monitors) {
        if ((!preferred.empty() && monitor.id == preferred) || (!chosen && monitor.primary)) {
            chosen = &monitor;
        }
    }
    if (!chosen) {
        // No monitor reported: the main monitor's rectangle as Windows has it.
        MONITORINFO info = {sizeof(info)};
        GetMonitorInfoW(MonitorFromPoint({0, 0}, MONITOR_DEFAULTTOPRIMARY), &info);
        return info.rcMonitor;
    }
    const bool found = !preferred.empty() && chosen->id == preferred;
    static bool logged = false;
    if (!logged) {
        logged = true;
        re::Log("monitor: %ls %ldx%ld at (%ld,%ld)%s", chosen->name.c_str(), chosen->rect.right - chosen->rect.left,
                chosen->rect.bottom - chosen->rect.top, chosen->rect.left, chosen->rect.top,
                found ? "" : preferred.empty() ? ", main monitor" : ", preferred monitor not connected: main monitor");
    }
    return chosen->rect;
}

}  // namespace mods::monitor