Inside Qt for Symbian QApplication/zh

作者： "habert":http://developer.qt.nokia.com/member/3776

Qt for Symbian之程序启动

我们都知道Qt中只要构造出QApplication就启动了，可启动细节就很少有人知道了，当然我们编写Qt的程序无需关心这么多，这也是为什么要用Qt的原因，但如果能够了解则可以加深对Qt的认识。今天看了一下Qt for Symbian的源码，整理如下，希望对有兴趣的朋友有帮助：

QApplication::QApplication(int &amp;argc, char **argv)<br /> : QCoreApplication('''new QApplicationPrivate(argc, argv, GuiClient) //第一步) //第二步<br />{<br /> Q_D(QApplication); //第三步<br /> d->construct(); //第四步<br />}

第一步构造了QApplicationPrivate的实例，其中GuiClient是一个枚举常量，表示应用程序的类型，这里我们不用关心。说道 QApplicationPrivate，如果你看过Qt的源码，你会发现很多类都配对有相应的Private类，这是Qt在封装底层实现时经常用的一种模式，Handle-Body Design Pattern，也就是说你在xx类中看不到具体的实现，具体的实现都封装在xxPrivate类中，而在xx类的方法只是调用xxPrivate中相应的方法。
第二步用QApplicationPrivate的实例构造了QCoreApplication，这里调用的是QCoreApplication的QCoreApplication::QCoreApplication(QCoreApplicationPrivate &p)构造函数，代码如下：

QCoreApplication::QCoreApplication(QCoreApplicationPrivate &amp;p)<br /> : QObject(p, 0)<br />{<br /> init();<br /> // note: it is the subclasses' job to call<br /> // QCoreApplicationPrivate::eventDispatcher->startingUp();<br />}

上面代码中的init初始化了一些资源，其中包括事件分发器。
第三步定义了d,这里是通过宏Q_D来实现的，其中宏Q_D的定义如下：

#define Q_D(Class) Class##Private''' const d = d_func()<code><br />所以这里的d即是调用父类构造函数QCoreApplication(*new QApplicationPrivate(argc, argv, GuiClient)时创建的QApplicationPrivate实例。

第四步调用d的construct函数，也就是QApplicationPrivate的实例的construct函数。代码如下所示：<br />

void QApplicationPrivate::construct(
#ifdef Q_WS_X11
Display *dpy, Qt::HANDLE visual, Qt::HANDLE cmap
#endif
)
{
initResources();

qt_is_gui_used = (qt_appType != QApplication::Tty);
process_cmdline();
// the environment variable has the lowest precedence of runtime graphicssystem switches
if (graphics_system_name.isEmpty())
graphics_system_name = QString::fromLocal8Bit(qgetenv("QT_GRAPHICSSYSTEM"));
// Must be called before initialize()
//这里调用了qt_init
qt_init(this, qt_appType
#ifdef Q_WS_X11
, dpy, visual, cmap
#endif
);
initialize();
eventDispatcher->startingUp();

1. ifdef QT_EVAL
   extern void qt_gui_eval_init(uint);
   qt_gui_eval_init(application_type);
   #endif

1. if defined(Q_OS_SYMBIAN) && !defined(QT_NO_SYSTEMLOCALE)
   symbianInit();
   #endif

1. ifndef QT_NO_LIBRARY
   if(load_testability) {
   QLibrary testLib(QLatin1String("qttestability"));
   if (testLib.load()) {
   typedef void (TasInitialize)(void);
   TasInitialize initFunction = (TasInitialize)testLib.resolve("qt_testability_init");
   if (initFunction) {
   initFunction();
   } else {
   qCritical("Library qttestability resolve failed!");
   }
   } else {
   qCritical("Library qttestability load failed!");
   }
   }

//make sure the plugin is loaded
if (qt_is_gui_used)
qt_guiPlatformPlugin();
#endif
}

<br />这里也是初始化了很多资源，其中要要说的是qt_init，因为就是它创建了程序，代码如下：<br />

void qt_init(QApplicationPrivate /* priv */, int)
{
if (!CCoeEnv::Static()) {
// The S60 framework creates a new trap handler which will render any existing traps
// invalid as long as it is active. This means that all code in main() that occurs after
// the QApplication construction needs to be surrounded by a new trap, despite having
// an outer one already. To avoid this, we save the original trap handler here, and set
// it back after the S60 framework is constructed. Then we restore it right before the S60
// framework destruction.
TTrapHandler origTrapHandler = User::TrapHandler();

// The S60 framework has not been initialized. We need to do it.
//这里就是创建程序的地方
TApaApplicationFactory factory(S60->s60ApplicationFactory ?
S60->s60ApplicationFactory : newS60Application);
CApaCommandLine commandLine = 0;
TInt err = CApaCommandLine::GetCommandLineFromProcessEnvironment(commandLine);
// After this construction, CEikonEnv will be available from CEikonEnv::Static().
// (much like our qApp).
CEikonEnv* coe = new CEikonEnv;
//not using QT_TRAP_THROWING, because coe owns the cleanupstack so it can't be pushed there.
if(err == KErrNone)
TRAP (err, coe->ConstructAppFromCommandLineL(factory,*commandLine)); //这里通过factory创建了程序
delete commandLine;
if(err != KErrNone) {
qWarning() << "qt_init: Eikon application construct failed ("
<< err
<< "), maybe missing resource file on S60 3.1?";
delete coe;
qt_symbian_throwIfError(err);
}

S60->s60InstalledTrapHandler = User::SetTrapHandler(origTrapHandler);

S60->qtOwnsS60Environment = true;
} else {
S60->qtOwnsS60Environment = false;
}

1. ifdef QT_NO_DEBUG
   if (!qgetenv("QT_S60_AUTO_FLUSH_WSERV").isEmpty())
   #endif
   S60->wsSession().SetAutoFlush(ETrue);

1. ifdef Q_SYMBIAN_WINDOW_SIZE_CACHE
   TRAP_IGNORE(S60->wsSession().EnableWindowSizeCacheL());
   #endif

S60->updateScreenSize();

TDisplayMode mode = S60->screenDevice()->DisplayMode();
S60->screenDepth = TDisplayModeUtils::NumDisplayModeBitsPerPixel(mode);

//NB: RWsSession::GetColorModeList tells you what window modes are supported,
//not what bitmap formats.
if(QSysInfo::symbianVersion() == QSysInfo::SV_9_2)
S60->supportsPremultipliedAlpha = 0;
else
S60->supportsPremultipliedAlpha = 1;

RProcess me;
TSecureId securId = me.SecureId();
S60->uid = securId.operator TUid();

// enable focus events - used to re-enable mouse after focus changed between mouse and non mouse app,
// and for dimming behind modal windows
S60->windowGroup().EnableFocusChangeEvents();

//Check if mouse interaction is supported (either EMouse=1 in the HAL, or EMachineUID is one of the phones known to support this)
const TInt KMachineUidSamsungI8510 = 0x2000C51E;
// HAL::Get(HALData::EPen, TInt&amp; result) may set 'result' to 1 on some 3.1 systems (e.g. N95).
// But we know that S60 systems below 5.0 did not support touch.
static const bool touchIsUnsupportedOnSystem =
QSysInfo::s60Version() QSysInfo::SV_S60_3_1

       || QSysInfo::s60Version()  QSysInfo::SV_S60_3_2;
 TInt machineUID;
 TInt mouse;
 TInt touch;
 TInt err;
 err = HAL::Get(HALData::EMouse, mouse);
 if (err != KErrNone)
 mouse = 0;
 err = HAL::Get(HALData::EMachineUid, machineUID);
 if (err != KErrNone)
 machineUID = 0;
 err = HAL::Get(HALData::EPen, touch);
 if (err != KErrNone || touchIsUnsupportedOnSystem)
 touch = 0;
#ifdef WINS
 if(QSysInfo::symbianVersion() <= QSysInfo::SV_9_4) {
 //for symbian SDK emulator, force values to match typical devices.
 mouse = 0;
 touch = touchIsUnsupportedOnSystem ? 0 : 1;
 }
#endif
 if (mouse || machineUID == KMachineUidSamsungI8510) {
 S60->hasTouchscreen = false;
 S60->virtualMouseRequired = false;
 }
 else if (!touch) {
 S60->hasTouchscreen = false;
 S60->virtualMouseRequired = true;
 }
 else {
 S60->hasTouchscreen = true;
 S60->virtualMouseRequired = false;
 }

S60->avkonComponentsSupportTransparency = false;
S60->menuBeingConstructed = false;

1. ifdef Q_WS_S60
   TUid KCRUidAvkon = { 0x101F876E };
   TUint32 KAknAvkonTransparencyEnabled = 0x0000000D;

CRepository* repository = 0;
TRAP (err, repository = CRepository::NewL(KCRUidAvkon));

if(err KErrNone) {

       TInt value = 0;
       err = repository->Get(KAknAvkonTransparencyEnabled, value);
       if(err  KErrNone) {
 S60->avkonComponentsSupportTransparency = (value==1) ? true : false;
 }
 }
 delete repository;
 repository = 0;
#endif

1. ifdef QT_KEYPAD_NAVIGATION
   if (touch) {
   QApplicationPrivate::navigationMode = Qt::NavigationModeNone;
   } else {
   QApplicationPrivate::navigationMode = Qt::NavigationModeKeypadDirectional;
   }
   #endif

1. ifndef QT_NO_CURSOR
   //Check if window server pointer cursors are supported or not
   #ifndef Q_SYMBIAN_FIXED_POINTER_CURSORS
   //In generic binary, use the HAL and OS version
   //Any other known good phones should be added here.
   if (machineUID == KMachineUidSamsungI8510 || (QSysInfo::symbianVersion() != QSysInfo::SV_9_4
   && QSysInfo::symbianVersion() != QSysInfo::SV_9_3 && QSysInfo::symbianVersion()
    != QSysInfo::SV_9_2)) {
   S60->brokenPointerCursors = false;
   qt_symbian_setWindowGroupCursor(Qt::ArrowCursor, S60->windowGroup());
   }
   else
   S60->brokenPointerCursors = true;
   #endif

if (S60->mouseInteractionEnabled) {
#ifndef Q_SYMBIAN_FIXED_POINTER_CURSORS
if (S60->brokenPointerCursors) {
qt_symbian_set_pointer_sprite(Qt::ArrowCursor);
qt_symbian_show_pointer_sprite();
}
else
#endif
S60->wsSession().SetPointerCursorMode(EPointerCursorNormal);
}
#endif

QFont systemFont;
systemFont.setFamily(systemFont.defaultFamily());
QApplicationPrivate::setSystemFont(systemFont);

1. ifdef SYMBIAN_GRAPHICS_WSERV_QT_EFFECTS
   QObject::connect(qApp, SIGNAL (aboutToQuit()), qApp, SLOT (_q_aboutToQuit()));
   #endif

/*
### Commented out for now as parameter handling not needed in SOS (yet). Code below will break testlib with -o flag
int argc = priv->argc;
char **argv = priv->argv;

// Get command line params
int j = argc ? 1 : 0;
for (int i=1; i<argc; i+) {
if (argv[i] && *argv[i] != '-') {
argv[j+] = argv[i];
continue;
}

1. if defined(QT_DEBUG)
   if (qstrcmp(argv[i], "-nograb") == 0)
   appNoGrab = !appNoGrab;
   else
   #endif // QT_DEBUG
    ;
   }
   */

// Register WId with the metatype system. This is to enable
// QWidgetPrivate::create_sys to used delayed slot invocation in order
// to destroy WId objects during reparenting.
qRegisterMetaType<WId>("WId");
}

<br />代码很多，哈哈。上面代码中标有注释“这里就是创建程序的地方” 的部分:<br />

TApaApplicationFactory factory(S60->s60ApplicationFactory ?
S60->s60ApplicationFactory : newS60Application);

<br />这里将newS60Application赋值给S60->s60ApplicationFactory，而newS60Application是什么呢，我们看看它的定义：<br />

CApaApplication newS60Application()
{
return new QS60MainApplication;
}

<br />由此可知newS60Application就是一个函数指针，它创建了一个QS60MainApplication实例，这里QS60MainApplication类封装了CAknApplication的实现。<br />另外上面代码中s60是一个全局数据，里面放了很多东西，主要是方便直接查询，其类结构如下：<br />

class QS60Data
{
public:
QS60Data();
QThreadStorage<QS60ThreadLocalData> tls;
TUid uid;
int screenDepth;
QPoint lastCursorPos;
QPoint lastPointerEventPos;
QPointer<QWidget> lastPointerEventTarget;
QPointer<QWidget> mousePressTarget;
int screenWidthInPixels;
int screenHeightInPixels;
int screenWidthInTwips;
int screenHeightInTwips;
int defaultDpiX;
int defaultDpiY;
WId curWin;
enum PressedKeys {
Select = 0x1,
Right = 0x2,
Down = 0x4,
Left = 0x8,
Up = 0x10,
LeftUp = 0x20,
RightUp = 0x40,
RightDown = 0x80,
LeftDown = 0x100
};
int virtualMousePressedKeys; // of the above type, but avoids casting problems
int virtualMouseAccelDX;
int virtualMouseAccelDY;
QElapsedTimer virtualMouseAccelTimeout;
int virtualMouseMaxAccel;
#ifndef Q_SYMBIAN_FIXED_POINTER_CURSORS
int brokenPointerCursors : 1;
#endif
int hasTouchscreen : 1;
int mouseInteractionEnabled : 1;
int virtualMouseRequired : 1;
int qtOwnsS60Environment : 1;
int supportsPremultipliedAlpha : 1;
int avkonComponentsSupportTransparency : 1;
int menuBeingConstructed : 1;
QApplication::QS60MainApplicationFactory s60ApplicationFactory; // typedef'ed pointer type

enum ScanCodeState {
Unpressed,
KeyDown,
KeyDownAndKey
};
QHash<TInt, ScanCodeState> scanCodeStates;

static inline void updateScreenSize();
inline RWsSession&amp; wsSession();
static inline RWindowGroup&amp; windowGroup();
inline CWsScreenDevice* screenDevice();
static inline CCoeAppUi* appUi();
static inline CEikMenuBar* menuBar();
#ifdef Q_WS_S60
static inline CEikStatusPane* statusPane();
static inline CCoeControl* statusPaneSubPane(TInt aPaneId);
static inline CAknTitlePane* titlePane();
static inline CAknContextPane* contextPane();
static inline CEikButtonGroupContainer* buttonGroupContainer();
static void setStatusPaneAndButtonGroupVisibility(bool statusPaneVisible, bool buttonGroupVisible);
#endif
static void controlVisibilityChanged(CCoeControl *control, bool visible);

1. ifdef Q_OS_SYMBIAN
   TTrapHandler *s60InstalledTrapHandler;
   #endif
   };