Wiley.Symbian.OS.Internals.Real.time.Kernel.Programming.Dec.2005.eBook-DDU (779891), страница 94
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This type of anim DLL is now called a ‘‘windowanim’’, and to create one you would return an object derived fromCWindowAnim from CreateInstanceL().To provide digital ink on-screen, we developed a new type of animthat allowed drawing to a sprite.
This is known as a ‘‘sprite anim’’, and444THE WINDOW SERVERto create one you would return an object derived from CSpriteAnimfrom CreateInstanceL(). The relationships between these, and other,classes are shown in Figure 11.2.MEventHandlerCBaseCGraphicsContextOfferRawEvent()CBitmapContextCAnimiFunctionsAnimate()Command()CommandReplyL()CSpriteAnimiSpriteFunctionsCAnimGcCWindowAnimiWindowFunctionsFocusChanged()Redraw()Figure 11.2 Animation class hierarchyThere are two types of functions in the anim interface.
Firstly, there arefunctions in the anim that WSERV calls. These are shown in the diagramas member functions of the four classes: MEventHandler, CAnim,CSpriteAnim and CWindowAnim; they are all pure virtual functionsand so the anim writer has to provide implementations for the relevantset of these functions, depending on which class she has derived from.The WSERV functions that an anim can call are provided by means ofthe member data shown in Figure 11.2.
There are four in all, shown withthe class they belong to in parentheses:• iFunctions (MAnimGeneralFunctions)• iSpriteFunctions (MAnimSpriteFunctions)• iWindowFunctions (MAnimWindowFunctions)• iGc (CAnimGc).CAnimGc provides drawing functions that the window anim uses to drawto its window.Thus our example CHandWritingAnim is a sub-class of CSpriteAnim.A SIMPLE HANDWRITING ANIMATION DLL44511.7.3 Functions a sprite anim must provideAll the derived classes of CSpriteAnim must provide all the virtualfunctions of that class, CAnim and MEventHandler, so part of our classdefinition will be:class CHandWritingAnim : public CSpriteAnim{public:∼CHandWritingAnim();//pure virtual functions from CSpriteAnimvoid ConstructL(TAny* aArgs);//pure virtual functions from MEventHandlerTBool OfferRawEvent(const TRawEvent& aRawEvent);//pure virtual functions from CAnimvoid Animate(TdateTime* aDateTime);void Command(TInt aOpcode,TAny* aArgs);TInt CommandReplyL(TInt aOpcode,TAny* aArgs);private:TInt iState;CFbsBitmapDevice* iBitmapDevice;CFbsBitmapDevice* iMaskBitmapDevice;CFbsBitGc* iSpriteGc;TBool iIsMask;CPointStore* iPointStore;};I will talk about the purpose of these functions in the followingsections.11.7.3.1 ConstructionThe first anim DLL function that will be called is CSpriteAnim::ConstructL.
WSERV calls this function when responding to the client’scall to RAnim::Construct(). The parameter aArgs passed to theConstructL function is a pointer to a copy of the content of thedescriptor that was originally passed in to the client-side Constructfunction. It will normally need casting to the correct type.void CHandWritingAnim::ConstructL(TAny* ){TSpriteMember* spriteMember=iSpriteFunctions->GetSpriteMember(0);iIsMask=(spriteMember->iBitmap->Handle()!=spriteMember->iMaskBitmap->Handle());iBitmapDevice=CFbsBitmapDevice::NewL(spriteMember->iBitmap);if (iIsMask)iMaskBitmapDevice=CFbsBitmapDevice::NewL(spriteMember->iMaskBitmap);iSpriteGc=CFbsBitGc::NewL();iSpriteGc->Reset();iState=EHwStateInactive;446THE WINDOW SERVERiPointStore=new(ELeave) CPointStore();iPointStore->ConstructL();iSpriteFunctions->SizeChangedL();...}The call to GetSpriteMember() returns details of the sprite that thisanim is allowed to draw to.
Usually, sprites can animate. To do this, aclient needs to give a sprite several members – each member containsone frame of the animation. In this case, the client only needs to createone frame for the ink and thus we specify a value of ‘‘0’’ as the parameterin this function call. This is then checked to see if the client has providedseparate bitmaps for the mask and the sprite content.
Drawing to anygraphics object, such as a bitmap or the screen, requires a device forthat object. From a device, we can create a graphics context (or GC)and use this to do the drawing. We now create the following objects – aCFbsBitmapDevice for each bitmap and a single CFbsBitGc whichcan be used on both bitmaps.The state member, iState, is initialized to say that no handwritingrecognition is currently required. Since the shape drawn on the screen isto be converted to a character, we create a point store so that the detailedshape of the ink can be recorded. The call to SizeChangedL() is partof the standard, general initialization of a sprite.
It sets up the backupbitmap for the sprite, which needs to be the size of the largest frame. Thisfunction will go on to set the parameters for the ink, such as color andline width – this is not shown in the previous code segment.11.7.3.2 Receiving eventsEvents are received when WSERV calls the function: MEventHandler::OfferRawEvent(), see Section 11.3, How WSERV processesevents. Remember that this function was pure virtual in the base class,and so I have an implementation in my CHandwritingAnim class. Bydefault, WSERV will not pass events to anims, so if the anim wants toreceive the events, it has to call the function MAnimGeneralFunctions::GetRawEvents(), passing in the parameter ETrue.
Once anevent has been passed to the Anim DLL, it has to return a TBool to say ifit has consumed the event (ETrue) or not (EFalse):TBool CHandWritingAnim::OfferRawEvent(const TRawEvent &aRawEvent){if (iState==EHwStateDeactive)return EFalse;switch (aRawEvent.Type()){case TRawEvent::EButton1Down:A SIMPLE HANDWRITING ANIMATION DLL447return HandlePointerDown(aRawEvent.Pos());case TRawEvent::EPointerMove:return HandlePointerMove(aRawEvent.Pos());case TRawEvent::EButton1Up:return HandlePointerUp(aRawEvent.Pos());default:return EFalse;}}The first thing this function does is to check to see if handwriting isturned on.
If it is not, it will return EFalse to tell WSERV to processthe event itself. It also does this if the event is not a pointer event; thisis what the default part of the switch statement is for. This functionthen calls three other functions that will process the pointer events. Ihave not shown an implementation of these functions, but will note thatit would be advisable for them to adopt the strategy that if the userclicks and holds for a certain length of time, then this should be treatedas a pointer to be sent to applications, rather than for drawing digitalink.11.7.3.3 AnimatingThe Animate() function is designed for receiving periodic events toupdate the clock.void Animate(TDateTime* aDateTime);By default, WSERV does not call this virtual function.
If an anim doeswant it to be called, then the anim should call this function:void MAnimGeneralFunctions::SetSync(TAnimSync aSyncMode);The parameter specifies how often to call the Animate() function. Theoptions are:enum TAnimSync{ESyncNone,ESyncFlash,ESyncSecond,ESyncMinute,ESyncDay,};Clearly ESyncNone means that WSERV never animates. The remainingthree values tell WSERV to call the animate function after the specifiedtime intervals.448THE WINDOW SERVERThe second value is slightly different.
It tells WSERV to animate twicea second. However, these animations are not evenly spaced, every halfa second – they happen on the second and after 7/12 of a second. Thisis so that when the separator character (the ‘‘:’’ in ‘‘12:45:37’’) flashesit will be visible for slightly longer than it is invisible. (WSERV uses thesame internal timer to flash the cursor (and sprites), which also are visiblefor slightly longer than they are invisible.)To do these animations, WSERV uses a lock timer (possibly the onlyuse of a lock timer in Symbian OS).
This timer makes it easy for WSERVto determine if the system is running slowly. Its API is:void CTimer::Lock(TTimerLockSpec aLock);The parameter specifies a particular twelfth of a second. The first timethe function is called, the kernel will signal the associated active objectwhen it reaches that point in the second.
The second time the functionis called, the kernel will only signal the active object if the requestedtwelfth of the second is within a second of the first requested point. If itis not, the function will return with an error, showing that the system isvery busy.Suppose, for example, that a clock uses this timer to update a display ofseconds. Each second, the clock calls the lock timer to ask to be notifiedwhen the current second is over. At the next second boundary, the kernelsignals the active object. If the active object runs and re-queues itselfwithin that second, everything is fine. If the system is busy and by thetime the active object runs and re-queues itself, the second had passed,then the active object will complete with an error telling the clock that itneeds to reset itself, rather than just doing an increment.When WSERV gets an error back from the lock timer, it tells theanim that it should reset itself by passing the current date-time to theanimate function.
(When things are running normally, it passes NULL tothis function.)Although the handwriting anim does not need to do any animation,it does need a timer. Instead of creating its own timer, it uses theCTimer::Lock() function to receive timer notifications – I will saymore on this later.11.7.3.4 Client communicationThe following functions can both receive commands from the client side:TInt CAnim::CommandReplyL(TInt aOpcode, TAny* aArgs)=0;void CAnim::Command(TInt aOpcode, TAny* aArgs)=0;One difference between them is that the first one can also return a TIntvalue to the client. It can do this either by returning the value to send backA SIMPLE HANDWRITING ANIMATION DLL449to the client, or by leaving – the leave code will then be sent to the client.Another difference between these two functions is that the first one is sentdirectly to the window server.
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