The nexuslua function touserdata converts the given string to the Lua type light user data. It accepts a single parameter containing the string to convert and returns the value as light user data.

For an example, see poke.

Converting a C++ pointer to the correct format that touserdata can parse is done by assigning that pointer to an cbeam::container::xpod::type, which can be sent as part of message parameters. Example from acrion image framework:

explicit operator nexuslua::LuaTable() const
{
    if (Empty())
    {
        throw std::runtime_error("Error converting image to plugin parameters: image is empty");
    }

    nexuslua::LuaTable parameters;
    parameters.data[std::string(bufferKey)]        = Buffer();
    parameters.data[std::string(widthKey)]         = Width();
    parameters.data[std::string(heightKey)]        = Height();
    parameters.data[std::string(channelsKey)]      = Channels();
    parameters.data[std::string(depthKey)]         = Depth();
    parameters.data[std::string(minBrightnessKey)] = GetMinDisplayedBrightness();
    parameters.data[std::string(maxBrightnessKey)] = GetMaxDisplayedBrightness();

    return parameters;
}

The function Buffer() returns the pointer to the image buffer, which is assigned to an entry in a LuaTable that is later sent to an nexuslua agent as follows (example from acrionphoto):

void PluginManager::RunIoPluginMessage(const nexuslua::AgentMessage*                message,
                                    const std::string&                              fileName,
                                    std::shared_ptr<acrion::imageframework::Bitmap> pWorkingImage,
                                    std::shared_ptr<acrion::imageframework::Bitmap> pReferenceImage)
{
    bool        save;
    std::string filter;
    std::string title;

    const nexuslua::LuaTable     predefinedValues                             = PluginManager::AddImageParameters(pReferenceImage, pWorkingImage, nexuslua::LuaTable());
    nexuslua::LuaTable           parameterValues                              = predefinedValues;
    const nexuslua::sub_tables parameterDescriptionsWithDefaultValueOrUnset = message->GetDescriptionsOfUnsetParameters(predefinedValues);

    if (!areIOparams(parameterDescriptionsWithDefaultValueOrUnset, save, filter, title))
    {
        throw std::runtime_error("PluginManager::RunIoPluginMessage: '" + message->GetDisplayName() + "' is no I/O plugin message");
    }

    parameterValues.data[title] = fileName;
    parameterValues.SetReplyTo(Common::GetProductName().toStdString(), Common::GetReplyToMessageName());
    message->Send(parameterValues);
}

The LuaTable parameterValues includes the pointer to the buffer and is sent to an nexuslua agent via nexuslua::AgentMessage::Send in the last line of this method.

See also