OpenHarmony源码解析之获取显示状态功能

base/powermgr/display_manager
├── figures                   # 架构图
├── frameworks                  # FrameWork层
│   ├── napi                    # NAPI
│   └── native                  # Native层
├── interfaces                  # 接口层
│   ├── innerkits               # 内部 APIs
│   └── kits                    # 外部接口 APIs
├── sa_profile                  # SA 配置文件
├── service                     # 服务层
│   ├── native                  # Native 层
│   └── zidl                    # zidl 接口层
├── test                        # 测试用例
└── utils                       # 工具和通用层

//rk3568/base/powermgr/display_manager/service/native/src/display_system_ability.cpp
REGISTER_SYSTEM_ABILITY_BY_ID(DisplaySystemAbility, DISPLAY_MANAGER_SERVICE_ID, true);
//rk3568/foundation/distributedschedule/safwk/interfaces/innerkits/safwk/system_ability.h
#define REGISTER_SYSTEM_ABILITY_BY_ID(abilityClassName, systemAbilityId, runOnCreate) \
    const bool abilityClassName##_##RegisterResult = \
    SystemAbility::MakeAndRegisterAbility(new abilityClassName(systemAbilityId, runOnCreate));

//rk3568/base/powermgr/display_manager/service/native/src/display_system_ability.cpp

void DisplaySystemAbility::OnStart()
{
    DISPLAY_HILOGI(MODULE_SERVICE, "Start service");
    //将Display Power Manager Service服务发布到System Ability，此时DisplayPowerMgrService成为了显示能效管理服务提供端
    if (!Publish(DelayedSpSingleton<DisplayPowerMgrService>::GetInstance())) {
        DISPLAY_HILOGE(MODULE_SERVICE, "Failed to publish service");
    }
}

//rk3568/base/powermgr/display_manager/interfaces/kits/js/@ohos.brightness.d.ts
import { AsyncCallback } from './basic';
declare namespace brightness {
  function getState(): number;
  ...
}
export default brightness;

//rk3568/base/powermgr/display_manager/frameworks/napi/brightness.cpp
// 获取显示状态的NAPI接口初始化
static napi_value Init(napi_env env, napi_value exports)
{
    // 将JavaScript调用的getState NAPI接口实现声明为GetDisplayState函数
    napi_property_descriptor desc[] = {
        DECLARE_NAPI_FUNCTION("getState", GetDisplayState),
    };
    NAPI_CALL(env, napi_define_properties(env, exports, sizeof(desc) / sizeof(desc[0]), desc));
    DISPLAY_HILOGD(MODULE_JS_NAPI, "return");
    return exports;
}
//获取显示状态接口NAPI实现
static napi_value GetDisplayState(napi_env env, napi_callback_info info)
{
    DISPLAY_HILOGD(MODULE_JS_NAPI, "enter");
    size_t argc = 0;//参数个数
    napi_value args[1] = { 0 };//参数定义
    napi_value jsthis;//JS对象的this参数
    void *data = nullptr;//回调数据指针
    /* 根据环境变量获取参数 */
    napi_status status = napi_get_cb_info(env, info, &argc, args, &jsthis, &data);
    NAPI_ASSERT(env, (status == napi_ok) && (argc >= 0), "Bad parameters");
    napi_value result;
     // 调用客户端DisplayPowerMgrClient对象提供的GetDisplayState方法
    DisplayState state = DisplayPowerMgrClient::GetInstance().GetDisplayState();
    //创建js接口的返回值
    napi_create_uint32(env, static_cast<uint32_t>(state), &result);
    DISPLAY_HILOGD(MODULE_JS_NAPI, "return");
    return result;
}

//rk3568/base/powermgr/display_manager/frameworks/native/display_power_mgr_client.cpp
// 调用方不提供id参数，id默认为0，表示本地显示设备
DisplayState DisplayPowerMgrClient::GetDisplayState(uint32_t id)
{
    // 获取显示服务的代理端，这里返回的是DisplayPowerMgrProxy对象（service/zidl/src/display_power_mgr_proxy.cpp）
    auto proxy = GetProxy();
    if (proxy == nullptr) {
        //如果没有获取到proxy，则显示状态返回unknown
        return DisplayState::DISPLAY_UNKNOWN;
    }
     // 调用DisplayPowerMgrProxy的GetDisplayState，通过ipc方式获取显示状态结果
    return proxy->GetDisplayState(id);
}
// 获取显示管理服务提供的代理对象
sptr<IDisplayPowerMgr> DisplayPowerMgrClient::GetProxy()
{
    std::lock_guard lock(mutex_);
    if (proxy_ != nullptr) {
        return proxy_;
    }
    //  获取本设备内注册的SA的proxy
    sptr<ISystemAbilityManager> sam = SystemAbilityManagerClient::GetInstance().GetSystemAbilityManager();
    if (sam == nullptr) {
        DISPLAY_HILOGE(MODULE_INNERKIT, "Failed to get system ability manager");
        return nullptr;
    }
    // 检查显示管理服务是否注册
    sptr<IRemoteObject> obj = sam->CheckSystemAbility(DISPLAY_MANAGER_SERVICE_ID);
    if (obj == nullptr) {
        DISPLAY_HILOGE(MODULE_INNERKIT, "Failed to get display manager service");
        return nullptr;
    }
    sptr<IRemoteObject::DeathRecipient> dr = new DisplayDeathRecipient(*this);
    if ((obj->IsProxyObject()) && (!obj->AddDeathRecipient(dr))) {
        DISPLAY_HILOGE(MODULE_INNERKIT, "Failed to add death recipient");
        return nullptr;
    }
    // 将obj转换成IDisplayPowerMgr具体类型：DisplayPowerMgrProxy
    proxy_ = iface_cast<IDisplayPowerMgr>(obj);
    deathRecipient_ = dr;
    DISPLAY_HILOGI(MODULE_INNERKIT, "Succeed to connect display manager service");
    // 返回DisplayPowerMgrProxy对象
    return proxy_;
}

//rk3568/base/powermgr/display_manager/service/zidl/src/display_power_mgr_proxy.cpp
// 显示服务代理端显示状态获取功能实现
DisplayState DisplayPowerMgrProxy::GetDisplayState(uint32_t id)
{
    sptr<IRemoteObject> remote = Remote();
    RETURN_IF_WITH_RET(remote == nullptr, DisplayState::DISPLAY_UNKNOWN);
    uint32_t result = 0;
    MessageParcel data;
    MessageParcel reply;
    MessageOption option;
    if (!data.WriteInterfaceToken(DisplayPowerMgrProxy::GetDescriptor())) {
        DISPLAY_HILOGE(MODULE_INNERKIT, "DisplayPowerMgrClient::%{public}s write descriptor failed!", __func__);
        return DisplayState::DISPLAY_UNKNOWN;
    }
    WRITE_PARCEL_WITH_RET(data, Uint32, id, DisplayState::DISPLAY_UNKNOWN);
    // 将请求发送给显示服务的stub端，消息类型是GET_DISPLAY_STATE
    int ret = remote->SendRequest(static_cast<int>(IDisplayPowerMgr::GET_DISPLAY_STATE),
        data, reply, option);
    if (ret != ERR_OK) {
        DISPLAY_HILOGE(MODULE_INNERKIT, "DisplayPowerMgrProxy::%{public}s SendRequest is failed,%d", __func__, ret);
        return DisplayState::DISPLAY_UNKNOWN;
    }
    // 获取显示服务stub显示状态获取结果，如果无法获取结果，则返回unknown
    if (!reply.ReadUint32(result)) {
        DISPLAY_HILOGE(MODULE_INNERKIT, "Readback fail!");
        return DisplayState::DISPLAY_UNKNOWN;
    }
    // 返回显示服务stub端执行结果
    return static_cast<DisplayState>(result);
}

//rk3568/base/powermgr/display_manager/service/zidl/src/display_power_mgr_stub.cpp
// 处理显示管理代理端发送的请求
int32_t DisplayPowerMgrStub::OnRemoteRequest(uint32_t code, MessageParcel &data, MessageParcel &reply,
    MessageOption &option)
{
    DISPLAY_HILOGD(MODULE_SERVICE, "DisplayPowerMgrStub::OnRemoteRequest, cmd = %d, flags= %d",
        code, option.GetFlags());
    std::u16string descripter = DisplayPowerMgrStub::GetDescriptor();
    std::u16string remoteDescripter = data.ReadInterfaceToken();
    if (descripter != remoteDescripter) {
        DISPLAY_HILOGE(MODULE_SERVICE, "DisplayPowerMgrStub::OnRemoteRequest failed, descriptor is not matched!");
        return E_GET_POWER_SERVICE_FAILED;
    }
    switch (code) {
        ...
        // 消息类型为GET_BRIGHTNESS的处理函数    
        case static_cast<int32_t>(IDisplayPowerMgr::GET_DISPLAY_STATE):
            ret = GetDisplayStateStub(data, reply);
            break;
        ...
        default:
            return IPCObjectStub::OnRemoteRequest(code, data, reply, option);
    }
}
// 显示亮度获取stub端处理函数
int32_t DisplayPowerMgrStub::GetDisplayStateStub(MessageParcel& data, MessageParcel& reply)
{
    uint32_t id = 0;
    READ_PARCEL_WITH_RET(data, Uint32, id, E_READ_PARCEL_ERROR);
    // 调用子类DisplayPowerMgrService的GetDisplayState方法
    DisplayState ret = GetDisplayState(id);
    // 将调用结果发送给显示管理代理端
    if (!reply.WriteUint32(static_cast<uint32_t>(ret))) {
        DISPLAY_HILOGE(MODULE_SERVICE, "Failed to write GetDisplayStateStub return value");
        return E_WRITE_PARCEL_ERROR;
    }
    return ERR_OK;
}

//rk3568/base/powermgr/display_manager/service/native/src/display_power_mgr_service.cpp
// 显示管理服务端获取显示状态实现函数
DisplayState DisplayPowerMgrService::GetDisplayState(uint32_t id)
{
    DISPLAY_HILOGI(MODULE_SERVICE, "GetDisplayState %{public}d", id);
    //根据设备id找到对应的ScreenController对象，如果没找到则返回unknown
    auto iterater = controllerMap_.find(id);
    if (iterater == controllerMap_.end()) {
        return DisplayState::DISPLAY_UNKNOWN;
    }
    // 返回ScreenController的GetState调用结果
    return iterater->second->GetState();
}

//rk3568/base/powermgr/display_manager/service/native/src/screen_controller.cpp
class ScreenController :
    public AnimateCallback,
    public std::enable_shared_from_this<ScreenController> {
public:
    ...
    DisplayState GetState()
    {
        //直接返回自身的私有成员变量state_
        return state_;
    };
    //ScreenController私有成员变量state_可通过其公共方法UpdateState去改变
    bool UpdateState(DisplayState state, uint32_t reason);
    ...
private:
    ...
    DisplayState state_;
    std::map<DisplayState, uint32_t> stateValues_;
    ...
};
//ScreenController在构造时会加载系统所支持的四个状态（on，dim，off，suspend）到map中，此时state_默认构造为on状态
ScreenController::ScreenController(uint64_t devId, std::shared_ptr<ScreenAction> action)
    : devId_(devId), state_(DisplayState::DISPLAY_ON), action_(action)
{
    DISPLAY_HILOGI(MODULE_SERVICE, "ScreenController created: %{public}d", static_cast<uint32_t>(devId_));
    stateValues_.emplace(DisplayState::DISPLAY_ON, DISPLAY_FULL_BRIGHTNESS);
    stateValues_.emplace(DisplayState::DISPLAY_DIM, DISPLAY_DIM_BRIGHTNESS);
    stateValues_.emplace(DisplayState::DISPLAY_OFF, DISPLAY_OFF_BRIGHTNESS);
    stateValues_.emplace(DisplayState::DISPLAY_SUSPEND, DISPLAY_SUSPEND_BRIGHTNESS);
    animator_ = nullptr;
}