vdi-cloud/terminal/native-cursor/vdi_native_cursor.h

#pragma once

#include <QFile>
#include <QImage>
#include <QSaveFile>
#include <QtEndian>
#include <time.h>
#include "input/input.h"
#include "streamutils.h"

// Linux X11 single-seat native cursor. Called only by the SDL main thread.
// The producer starts cursor-free before this session's first captured frame.
class VdiNativeCursor {
public:
    VdiNativeCursor(SDL_Window* window, SdlInputHandler* input) :
        m_Window(window), m_Input(input), m_Path(qgetenv("VDI_NATIVE_CURSOR_STATE")),
        m_Epoch(qgetenv("VDI_NATIVE_CURSOR_EPOCH").toULongLong()) {}

    bool enabled() const { return !m_Path.isEmpty(); }

    void observe(const SDL_Event& event) {
        if (event.type == SDL_MOUSEMOTION || event.type == SDL_MOUSEBUTTONDOWN ||
                event.type == SDL_MOUSEBUTTONUP) {
            m_LastInput = nowNs();
            ++m_InputSequence;
        }
    }

    bool tick() {
        if (!enabled()) return true;
        if (QByteArray(SDL_GetCurrentVideoDriver()) != "x11") return fail("requires X11 cursor backend");
        const quint64 pollTime = nowNs();
        if (pollTime - m_LastPoll < 4000000) return true;
        m_LastPoll = pollTime;
        QFile f(QString::fromUtf8(m_Path));
        if (!f.open(QIODevice::ReadOnly) || f.size() < 76 || f.size() > 65608)
            return fail("missing or oversized state");
        const QByteArray packet = f.readAll();
        // The producer may atomically replace state after pollTime. Compare
        // against a timestamp taken AFTER the read, never before opening it.
        const quint64 now = nowNs();
        const auto* p = reinterpret_cast<const uchar*>(packet.constData());
        auto u32 = [p](int offset) { return qFromLittleEndian<quint32>(p + offset); };
        auto u64 = [p](int offset) { return qFromLittleEndian<quint64>(p + offset); };
        if (packet.left(8) != QByteArray("VDICUR1\0", 8) || u64(8) != m_Epoch ||
                u64(16) < m_Sequence || u64(24) > now || now - u64(24) > 2000000000)
            return fail("stale or mismatched lease");
        const int w = u32(32), h = u32(36), hx = u32(40), hy = u32(44);
        const int x = qint32(u32(48)), y = qint32(u32(52));
        const int sw = u32(56), sh = u32(60);
        if (w < 1 || w > 128 || h < 1 || h > 128 || hx < 0 || hx >= w ||
                hy < 0 || hy >= h || sw != 2560 || sh != 1440 ||
                x < 0 || x >= sw || y < 0 || y >= sh || packet.size() != 72 + w*h*4 ||
                !m_Input->isNativeCursorAbsoluteMode())
            return fail("unsupported shape, display or input mode");
        m_Sequence = u64(16);
        int ww, wh;
        SDL_GetWindowSize(m_Window, &ww, &wh);
        SDL_Rect src = {0, 0, sw, sh}, dst = {0, 0, ww, wh};
        StreamUtils::scaleSourceToDestinationSurface(&src, &dst);
        if (dst.w <= 0 || dst.h <= 0) return fail("empty viewport");
        const int cw = qMax(1, qRound(double(w) * dst.w / sw));
        const int ch = qMax(1, qRound(double(h) * dst.h / sh));
        if (cw > 256 || ch > 256) return fail("oversized scaled cursor");
        const quint64 acknowledged = u64(64 + w*h*4);
        const QByteArray pixels = packet.mid(64, w*h*4);
        if (pixels != m_Pixels || w != m_Width || h != m_Height || hx != m_HotX ||
                hy != m_HotY || dst.w != m_ViewWidth || dst.h != m_ViewHeight) {
            QImage image(reinterpret_cast<const uchar*>(pixels.constData()), w, h,
                         w * 4, QImage::Format_RGBA8888);
            image = image.scaled(cw, ch, Qt::IgnoreAspectRatio, Qt::FastTransformation);
            // SDL2's X11 Xcursor backend copies pixels without premultiplying.
            // XRender requires premultiplied channels, including antialiased edges.
            image = image.convertToFormat(QImage::Format_RGBA8888_Premultiplied);
            SDL_Surface* surface = SDL_CreateRGBSurfaceWithFormatFrom(
                image.bits(), cw, ch, 32, image.bytesPerLine(), SDL_PIXELFORMAT_RGBA32);
            if (!surface) return fail("SDL surface failed");
            SDL_Cursor* next = SDL_CreateColorCursor(surface,
                qMin(cw - 1, qRound(double(hx) * dst.w / sw)),
                qMin(ch - 1, qRound(double(hy) * dst.h / sh)));
            SDL_FreeSurface(surface);
            if (!next) return fail("SDL cursor failed");
            SDL_SetCursor(next);
            if (m_Cursor) SDL_FreeCursor(m_Cursor);
            m_Cursor = next;
            m_Pixels = pixels;
            m_Width = w; m_Height = h; m_HotX = hx; m_HotY = hy;
            m_ViewWidth = dst.w; m_ViewHeight = dst.h;
            SDL_LogInfo(SDL_LOG_CATEGORY_APPLICATION,
                        "VDI native shape: %dx%d hotspot=%d,%d sequence=%llu",
                        w, h, hx, hy, (unsigned long long)m_Sequence);
        }
        int mx, my;
        const auto buttons = SDL_GetMouseState(&mx, &my);
        const bool inside = mx >= dst.x && my >= dst.y && mx < dst.x + dst.w && my < dst.y + dst.h;
        const bool focused = SDL_GetKeyboardFocus() == m_Window;
        if (m_PublishedInput != m_InputSequence) {
            QByteArray message(16, '\0');
            qToLittleEndian<quint64>(m_InputSequence, reinterpret_cast<uchar*>(message.data()));
            qToLittleEndian<qint32>(qBound(0, (mx-dst.x)*sw/dst.w, sw-1),
                                   reinterpret_cast<uchar*>(message.data()+8));
            qToLittleEndian<qint32>(qBound(0, (my-dst.y)*sh/dst.h, sh-1),
                                   reinterpret_cast<uchar*>(message.data()+12));
            QSaveFile outgoing(QString::fromUtf8(m_Path)+".input");
            if (!outgoing.open(QIODevice::WriteOnly) || outgoing.write(message) != 16 || !outgoing.commit())
                return fail("input acknowledgement file failed");
            m_PublishedInput = m_InputSequence;
        }
        m_Input->enableNativeCursorVisibility();
        SDL_SetCursor(focused && inside ? m_Cursor : SDL_GetDefaultCursor());
        // Initial alignment, and host-initiated warps only after local input has
        // settled. Never pull the pointer back using delayed motion echoes.
        if (focused && inside && !buttons && acknowledged == m_InputSequence &&
                now - m_LastInput > 500000000) {
            const int tx = dst.x + qRound(double(x) * dst.w / sw);
            const int ty = dst.y + qRound(double(y) * dst.h / sh);
            if (qAbs(tx - mx) > 2 || qAbs(ty - my) > 2) {
                // SDL2's X11 in-window warp is a no-op with pointer barriers
                // (used by fullscreen absolute mode). Global warp honors this
                // in-viewport target while actually moving the native pointer.
                int wx, wy;
                SDL_GetWindowPosition(m_Window, &wx, &wy);
                if (SDL_WarpMouseGlobal(wx+tx, wy+ty) < 0)
                    return fail("host cursor warp failed");
                m_LastInput = now;
            }
        }
        return true;
    }

    void shutdown() {
        if (m_Cursor) {
            SDL_SetCursor(SDL_GetDefaultCursor());
            SDL_FreeCursor(m_Cursor);
            m_Cursor = nullptr;
        }
    }

private:
    static quint64 nowNs() {
        struct timespec t;
        clock_gettime(CLOCK_MONOTONIC, &t);
        return quint64(t.tv_sec)*1000000000 + t.tv_nsec;
    }
    bool fail(const char* reason) {
        SDL_LogError(SDL_LOG_CATEGORY_APPLICATION, "VDI native cursor ended: %s", reason);
        shutdown();
        return false;
    }
    SDL_Window* m_Window;
    SdlInputHandler* m_Input;
    QByteArray m_Path, m_Pixels;
    quint64 m_Epoch, m_Sequence = 0, m_LastPoll = 0, m_LastInput = nowNs();
    quint64 m_InputSequence = 0, m_PublishedInput = 0;
    SDL_Cursor* m_Cursor = nullptr;
    int m_Width = 0, m_Height = 0, m_HotX = 0, m_HotY = 0;
    int m_ViewWidth = 0, m_ViewHeight = 0;
};