kate-deft/src/plugin/waylandcursorwarp.cpp

/*
 * SPDX-License-Identifier: LGPL-2.0-or-later
 */
#include "waylandcursorwarp.h"

#include <QGuiApplication>
#include <QTimer>
#include <QWindow>
#include <qpa/qplatformnativeinterface.h>

#include <QtGui/qguiapplication_platform.h> // QNativeInterface::QWaylandApplication

#include <wayland-client.h>
#include "wayland-pointer-constraints-unstable-v1-client-protocol.h"

namespace katecustom
{

namespace
{
// --- registry listener trampoline ---------------------------------------
void registryGlobal(void *data, wl_registry *registry, uint32_t name,
                     const char *interface, uint32_t version)
{
    static_cast<WaylandCursorWarp *>(data)->onGlobal(registry, name, interface, version);
}
void registryGlobalRemove(void *, wl_registry *, uint32_t) {}

const wl_registry_listener kRegistryListener = {
    registryGlobal,
    registryGlobalRemove,
};

// Pull a wl_* handle out of Qt's Wayland application native interface.
QNativeInterface::QWaylandApplication *waylandApp()
{
    return qGuiApp->nativeInterface<QNativeInterface::QWaylandApplication>();
}
} // namespace

WaylandCursorWarp::WaylandCursorWarp(QObject *parent)
    : QObject(parent)
{
}

WaylandCursorWarp::~WaylandCursorWarp()
{
    if (m_constraints) {
        zwp_pointer_constraints_v1_destroy(m_constraints);
        m_constraints = nullptr;
    }
}

bool WaylandCursorWarp::isWaylandSession()
{
    return QGuiApplication::platformName().startsWith(QLatin1String("wayland"));
}

void WaylandCursorWarp::onGlobal(wl_registry *registry, uint32_t name,
                                 const char *interface, uint32_t version)
{
    if (qstrcmp(interface, zwp_pointer_constraints_v1_interface.name) == 0) {
        // Bind at most the version we were built against.
        const uint32_t bindVersion =
            qMin<uint32_t>(version, zwp_pointer_constraints_v1_interface.version);
        m_constraints = static_cast<zwp_pointer_constraints_v1 *>(
            wl_registry_bind(registry, name, &zwp_pointer_constraints_v1_interface,
                             bindVersion));
    }
}

bool WaylandCursorWarp::ensureConstraints()
{
    if (m_constraints) {
        return true;
    }
    if (m_triedBind) {
        return false; // already looked; the compositor does not offer it
    }
    m_triedBind = true;

    auto *app = waylandApp();
    if (!app) {
        return false;
    }
    wl_display *display = app->display();
    if (!display) {
        return false;
    }
    wl_registry *registry = wl_display_get_registry(display);
    if (!registry) {
        return false;
    }
    wl_registry_add_listener(registry, &kRegistryListener, this);
    // Round-trip so the global advertisement is processed and onGlobal() runs.
    wl_display_roundtrip(display);
    wl_registry_destroy(registry);
    return m_constraints != nullptr;
}

bool WaylandCursorWarp::warp(QWindow *window, const QPointF &surfaceLocalPos)
{
    if (!window || !isWaylandSession()) {
        return false;
    }
    if (!ensureConstraints()) {
        return false;
    }

    auto *app = waylandApp();
    if (!app) {
        return false;
    }
    wl_pointer *pointer = app->pointer();
    wl_display *display = app->display();
    if (!pointer || !display) {
        return false;
    }

    QPlatformNativeInterface *pni = QGuiApplication::platformNativeInterface();
    if (!pni) {
        return false;
    }
    auto *surface = static_cast<wl_surface *>(
        pni->nativeResourceForWindow(QByteArrayLiteral("surface"), window));
    if (!surface) {
        return false;
    }

    // Lock the pointer to the surface it is already over, hint the target
    // position (surface-local), commit so the double-buffered hint is pending,
    // then release the lock — the compositor warps to the hint on unlock.
    zwp_locked_pointer_v1 *lock = zwp_pointer_constraints_v1_lock_pointer(
        m_constraints, surface, pointer, nullptr,
        ZWP_POINTER_CONSTRAINTS_V1_LIFETIME_ONESHOT);
    if (!lock) {
        return false;
    }
    zwp_locked_pointer_v1_set_cursor_position_hint(
        lock, wl_fixed_from_double(surfaceLocalPos.x()),
        wl_fixed_from_double(surfaceLocalPos.y()));
    wl_surface_commit(surface);
    wl_display_flush(display);

    // Release on the next event-loop turn: the lock must have been applied by
    // the compositor (pointer is over the surface) before we unlock, otherwise
    // the position hint is discarded. Destroying later keeps the sequence
    // compatible with compositors that apply the hint strictly on unlock.
    QTimer::singleShot(0, this, [lock, display]() {
        zwp_locked_pointer_v1_destroy(lock);
        wl_display_flush(display);
    });
    return true;
}

} // namespace katecustom