Ernest Laurentin11-Jul-02 10:34

11-Jul-02 10:34

You need to expose the property in the property map section
BEGIN_PROP_MAP(...)
I guess you want your control to load these properties at runtime!

Composite Property page control

srisan10-Jul-02 9:31

srisan

10-Jul-02 9:31

Hi all

I have a property page control and i want to insert another "custom control"(like FlexGrid control) in the property page's resource window. I tried making a CContainedWindow of the control inside my property page control. But unfortunately it got too complicated when it comes to handling events and setting properties for the custom control. Can someone suggest me how to do this (perhaps some sample code)or point me to any prev. article/link.

Thanks
srisan

Implemetation of Callback functions

wins10-Jul-02 2:12

wins

10-Jul-02 2:12

Hi Everybody,

Can anyone tell me how to implement a callback function in vc++ client for an ActiveX Server implemented in Visual Basic.

Add format for image icon on 2000 and XP file explorer

Anonymous9-Jul-02 2:48

Anonymous

9-Jul-02 2:48

Hello

With the file explorer on XP or 2000 , you can display image with the pellicule mode (or miniature)

But, windows displays only common format ( .jpg, tif, gif, ...)

So, my soft can read an other format (im5)

How can I complete the explorer display ? with a plug-in ?
with a link in th register table ?
with com object ?

thank you Blush | :O

Re: Add format for image icon on 2000 and XP file explorer

Anonymous13-Jul-02 6:59

Anonymous

13-Jul-02 6:59

Good question. I think it has to be a combination of a shell extension and a deskband. I know that in explorer, for a folder, you can edit the folder.htt file and modify the script to instantiate your COM object like the picture preview control that displays previews of common formats like jpg,bmp etc.

ObjectContext and it's role in COM+

MrGlover8-Jul-02 12:34

MrGlover

8-Jul-02 12:34

I have recently been re-evaluating the way our middle tier objects are designed and coded, including looking at their future under .Net

I guess to a large extent some of my methods of coding middle tier objects have been inherited from other people's code without a complete understanding of why. A few questions have arisen regarding the use of ObjectContext to create objects and so forth, especially in regard to COM+, but also wondering how things will change moving to .Net

1) All middle tier object instatiating (BLL creates DAL object, or BLL creates different BLL object) uses ObjectContext.CreateInstance. As I understand it, this will ensure the created object executes within the activity, the transaction (if there is one) and the security context of the client object.

Assuming my object is non transactional and I am not using security roles or such, do I still need to create objects in this manner?

2) Looking at the data access "helper" methods I see that someone has decided to ObjectContext.CreateInstance ADO objects. Is this wise? Are they threaded in such a way as to make them safe to run in an MTS activity?

3) All the documentation on ObjectContext talks about MTS, but there is no mention of it in the COM+ docs. Is there a good reason for this? What happened to ObjectContext in COM+?

4) In .Net it seems that my BLL and DAL objects would live in assemblies placed inteh ASP.Net Application's /bin/ directory and no longer require registering with COM+. Thank god I say, but are these assemblies still going to run under the supervision of COM+? And what happens to ObjectContexts under .Net?

Even if I could be pointed in the direction of some useful reading material that would be swell.

Re: ObjectContext and it's role in COM+

Paul Ingles20-Jul-02 13:54

Paul Ingles

20-Jul-02 13:54

JBoy wrote:
4) In .Net it seems that my BLL and DAL objects would live in assemblies placed inteh ASP.Net Application's /bin/ directory and no longer require registering with COM+. Thank god I say, but are these assemblies still going to run under the supervision of COM+? And what happens to ObjectContexts under .Net?

From what I've read any COM+ assemblies have to be registered in the GAC, and then referenced by managed code in the usual way. The assembly attributes specify how it is to be installed into COM+ without you doing much. However, if it needs to be referenced by unmanaged code then you have to do a little more (don't remember off the top of my head, sorry). As a result, I don't think you can do a regular xcopy deploy (which is what I assume you were meaning).

That's about the extent of my COM+ knowledge at the moment, looking to tackle it a bit more of the next few days!

Re: ObjectContext and it's role in COM+

MrGlover21-Jul-02 12:39

MrGlover

21-Jul-02 12:39

Most of those questions were regarding traditional COM+ dlls. However this last question was really concerning pure .Net assemblies.

Let me rephrase:

4) Rewriting my BLL and DAL objects in .Net, it seems that they would live in assemblies placed in the ASP.Net Application's /bin/ directory and no longer require registering with COM+. Thank god I say, but are these assemblies still going to run under the supervision of COM+ (IS there a COM+ in .Net)? And what happens to ObjectContexts under .Net?

Since part of the role of Contexts was to ensure that MTS could manage security roles, resource management and the like; I am guessing that these benefits are inherant with any managed code. Clearly I need to learn more about what happened to COM+ services with the advent of .Net

Re: ObjectContext and it's role in COM+

Paul Ingles22-Jul-02 4:10

Paul Ingles

22-Jul-02 4:10

As far as I understand it the assemblies are added to COM+ at the time they are requested by a client (provided you specify all the necessary attributes).

However, the only examples I've seen require that you register the assembly in the GAC, which requires you to run gacutil /i and thus have access to the server's command line. Now, your hosting Company may allow this, and they may be more willing to do it since its very straightforward and is unlikely to break support for anything else already in there.

I'm not too geared up on ObjectContexts (since I've only ever tried to use COM+ with .NET, and never really got into it with traditional VB6/ATL), take a look at the ServicedComponent class and it'll probably give you more info about context.

I'm not too sure whether COM+ security settings over-ride those set by the assembly attributes, or vice versa.

Drag n drop within IE

Per-Olov Jernberg8-Jul-02 1:43

Per-Olov Jernberg

8-Jul-02 1:43

Hi, i'm trying to create a component so i can implement file-drag&drop on a website.

i have looked at the messages received by IE in SPY++ and it shows no WM_DROPFILES messages :/
or can i receive the drop files message with standard dhtml?

dragging out of the page to the desktop is not a problem at the moment, but into the page.

any suggestions are welcome.

Re: Drag n drop within IE

Per-Olov Jernberg8-Jul-02 4:40

Per-Olov Jernberg

8-Jul-02 4:40

well, i managed to find another way of doing that (with the COleDropTarget/IDropTarget) and Register/Revoke-DragDrop()

so a solution is near Smile | :)

Re: Drag n drop within IE

Per-Olov Jernberg10-Jul-02 4:09

Per-Olov Jernberg

10-Jul-02 4:09

well, thanks for all answers, NOT. but i got it working.

Re: Drag n drop within IE

Paul Ingles20-Jul-02 13:50

Paul Ingles

20-Jul-02 13:50

Sounds mighty interesting, any chance I could persuade you to write an article up about it? Sorry I couldn't help, but I had absolutely no idea how to do it Smile | :)

Add ActiveX Control To ActiveX

7-Jul-02 3:11

I try to add Microsoft Comuincation Control to My ActiveX how can I
Cry | :((

Multiple clients accessing a COM component

Atin Kumar5-Jul-02 17:53

Atin Kumar

5-Jul-02 17:53

I have a COM component(STA). And 7 clients are trying to access that. After 2-3 sucessful calls for each client, one of the method of my COM component throws exception "-2147417848", which has hexa value: "80010108". MSDN does not tell how to rectify this problem. MSDN tells 3 possible reasons for such problem.

1. The server process ends (terminates).

This is not possible, as server is running.

2. The server process calls the CoDisconnectObject function.

I am not calling this method anyway.

3. No network communication is possible between the client and server computer for six minutes or more.

Client and server are on same PC. So, probably this can be ruled out.

Can anyone suggest something in this regard?

Regards.

Re: Multiple clients accessing a COM component

Vivek Rajan12-Jul-02 10:15

Vivek Rajan

12-Jul-02 10:15

Atin -

Atin Kumar wrote:
one of the method of my COM component throws exception "-2147417848", which has hexa value: "80010108".

Without knowing the details of your server, I can guess that this method is crashing the server.

From your description, it seems like other methods work fine.

HTH-
Vivek

Re: Multiple clients accessing a COM component

Atin Kumar14-Jul-02 15:05

Atin Kumar

14-Jul-02 15:05

Hi Vivek,

Thanks for replying to my query. I am further explaining the problem to you:

Server::
:::
Method A
Method B
Method C
Method D
:::

All the Clients are calling Method A, B, C, D in sequence. And exception comes in any of the above method. It is not that exception is thrown from a particular method. Chances of method crash are actually very very less.

Regards,
Atin.

Inheritence & Virtual functions with COM/ATL

Ed K5-Jul-02 8:39

Ed K

5-Jul-02 8:39

Disclaimer: I am not an ATL guru....want to be but that is another disclaimer!

I have not been able to find any samples to follow that use inheritence and virtual functions in com using atl. I guess the first question should be can it be done? Here is what I am trying to accomplish...

I have a parent object (PObject) that has a virtual function (ExecuteService), and several pure virtual functions such as Display(). I want to extend that class with several subclasses that would implement the specific service. (We need an insert diagram here button on this forum!)

I want a factory which takes a string or int which gives me the correct subclass depending upon the parameter value.

This should work:

void RunService(CString name)
{
    IServiceFactoryPtr ptrFact(__uuidof(ServiceFactory));
    IPObjectPtr ptrObj = ptrFact->GetServiceByName(name.AllocSysString());
    ptrObj->ExecuteService();
}

I've been able to get the factory working, I actually end up with the correct object when I make the call to GetServiceByName, however when calling ExecuteService I get an exception.

So, how do I set up the classes using ATL to get this to work??? It's a basic factory pattern. Good basis for an article if someone could get me past this hump!

Thanks,

ed

Re: Inheritence & Virtual functions with COM/ATL

mhamsa8-Jul-02 6:38

mhamsa

8-Jul-02 6:38

Take a look through the MS documentation (or other sources) for topics pertaining to Aggregation and/or containment. It is possible mimic inheritence in ATL by having one COM component aggregate the implementation of another COM component, expose these interfaces, and extend upon them by exposing additional interfaces. This is how inheritence in practiced in ATL and more specifically COM.

Re: Inheritence & Virtual functions with COM/ATL

soptest8-Jul-02 7:37

soptest

8-Jul-02 7:37

Component Categories

As this chapter has emphasized, the basic COM activation primitives require the caller to know the precise class name in order to create new instances. However, it is sometimes useful simply to request that any class that adheres to some semantic constraint is suitable. In addition, it could be useful to know what services a class requires from its clients prior to issuing an activation request to avoid creating objects that the client is not prepared to support properly. These problems motivate the concept of component categories.

COM allows implementors to group related COM classes into logical groups or component categories. Often, all classes within a category will implement the same set of interfaces. However, simply partitioning the class space based on which interfaces each class implements does not provide the proper granularity for many applications. Component categories act as metainformation that indicates which classes are compatible with particular semantic constraints.

A component category is a group of logically related COM classes that share a common category ID or CATID. CATIDs are GUIDs that are stored in the Registry as attributes of a class. Each class can have two subkeys: Implemented Categories and Required Categories. Assume that there are two categories of components: Simians and Mammals. These two categories would each have a unique CATID (CATID_Simians and CATID_Mammals, respectively). Assuming that the class Chimp is a member of each of these categories, the Chimp’s Implemented Categories registry key would contain each GUID as an individual subkey:

[HKCR\CLSID\{CLSID_Chimp}\Implemented Categories\{CATID_Mammals}]

[HKCR\CLSID\{CLSID_Chimp}\Implemented Categories\{CATID_Simians}]

These registry entries are typically added at self-registration time. Each known component category on a system has an entry under

HKEY_CLASSES_ROOT\Component Categories

Each category has its own unique subkey named by its CATID. Underneath its subkey, each category has one or more named values that contain the human-readable description of the category. For example, the two categories shown would require the following registry entries:

[HKCR\Component Categories\{CATID_Mammals}]
409="Bears live young"

[HKCR\Component Categories\{CATID_Simians}]
409="Eats Bananas"

Note that this example uses the 409 value, which is the LCID for U.S. English. Other locales can be supported by adding additional named values.

It is also possible for classes to indicate that they require particular types of functionality from the client. This support typically comes in the form of site interfaces that the client will provide to the object once activated. To allow these client-provided services to be categorized independent of any particular interface, COM allows classes to advertise a second type of category ID that can be used by clients to ensure that they do not activate a component that they cannot properly host. Assume the following two categories of client-

provided services: CATID_HasOxygen and CATID_HasWater. Since chimpanzees need oxygen and water to survive, the Chimp implementor might advertise that these two categories of client-provided services are required for activation. This is done by using the Required Categories subkeys:

[HKCR\CLSID\{CLSID_Chimp}\Required Categories\{CATID_HasOxygen}]

[HKCR\CLSID\{CLSID_Chimp}\Required Categories\{CATID_HasWater}]

These two category IDs would need to be registered under

HKEY_CLASSES_ROOT\Component Categories

as well. Given these entries, it is the client’s responsibility to ensure that it meets the required categories prior to activation. COM does not enforce client conformance.

Component category entries can be registered using either explicit registry functions or the COM-supplied component category manager. COM’s component category manager is exposed as an instantiable COM class (CLSID_ StdComponentCategoriesMgr) that implements the ICatRegister interface for registering category information and the ICatInformation interface for querying category information. The ICatRegister interface allows server DLLs easily to add the requisite entries to the Registry:

[ object, uuid(0002E012-0000-0000-C000-000000000046) ]
interface ICatRegister : IUnknown {
// description info for a category
  typedef struct tagCATEGORYINFO {
    CATID      catid;
    LCID       lcid;
    OLECHAR szDescription[128];
  } CATEGORYINFO;
// register cCts category descriptions
  HRESULT RegisterCategories([in] ULONG cCts, 
           [in, size_is(cCts)] CATEGORYINFO rgCatInfo[]);
// unregister cCategories category descriptions
  HRESULT UnRegisterCategories([in] ULONG cCategories, 
           [in, size_is(cCategories)] CATID rgcatid[]);
// indicate a class implements one or more categories
  HRESULT RegisterClassImplCategories([in] REFCLSID rclsid, 
           [in] ULONG cCategories, 
           [in, size_is(cCategories)] CATID rgcatid[]);
// deindicate a class implements with one or more categories
  HRESULT UnRegisterClassImplCategories([in] REFCLSID rclsd,
           [in] ULONG cCategories, 
           [in, size_is(cCategories)] CATID rgcatid[]);
// indicate a class requires one or more categories
  HRESULT RegisterClassReqCategories([in] REFCLSID rclsid, 
           [in] ULONG cCategories, 
           [in, size_is(cCategories)] CATID rgcatid[]);
// deindicate a class requires one or more categories
  HRESULT UnRegisterClassReqCategories([in] REFCLSID rclsid,
           [in] ULONG cCategories, 
           [in, size_is(cCategories)] CATID rgcatid[]);
}

There is no need for user-defined COM classes to implement this interface. It exists solely to allow servers to self-register their component categories using the COM-provided category manager implementation.

In the case of the Chimp example, the following code would register the correct information regarding each category:

// get the standard category manager
ICatRegister *pcr = 0;
HRESULT hr = CoCreateInstance( 
              CLSID_StdComponentCategoriesMgr, 0, 
              CLSCTX_ALL, IID_ICatRegister, (void**)&pcr);
if (SUCCEEDED(hr)) {
// build descriptions of each category
  CATEGORYINFO rgcc[4];
  rgcc[0].catid = CATID_Simian; 
  rgcc[1].catid = CATID_Mammal; 
  rgcc[2].catid = CATID_HasOxygen; 
  rgcc[3].catid = CATID_HasWater; 
  rgcc[0].lcid = rgcc[1].lcid 
    = rgcc[2].lcid = rgcc[3].lcid = 0x409;
  wcscpy(rgcc[0].szDescription, OLESTR("Eats Bananas"));
  wcscpy(rgcc[1].szDescription, OLESTR("Bears live young"));
  wcscpy(rgcc[2].szDescription, OLESTR("Provides Oxygen"));
  wcscpy(rgcc[3].szDescription, OLESTR("Provides Water"));
// register information regarding categories
  pcr->RegisterCategories(4, rgcc);

// note that Chimps are Simians and mammals
  CATID rgcid[2];
  rgcid[0] = CATID_Simian; rgcid[1] = CATID_Mammal;
  pcr->RegisterClassImplCategories(CLSID_Chimp, 2, rgcid);

// note that Chimps require Oxygen and Water
  rgcid[0] = CATID_HasOxygen; rgcid[1] = CATID_HasWater;
  pcr->RegisterClassReqCategories(CLSID_Chimp, 2, rgcid);
  pcr->Release();
}

Note that this code makes no raw registry API calls but instead uses the standard category manager to manipulate the Registry.

The standard category manager also allows applications to query the registry to find information regarding categories. This functionality is exposed via the ICatInformation interface:

[ object, uuid(0002E013-0000-0000-C000-000000000046) ]
interface ICatInformation : IUnknown {
// get list of known categories
  HRESULT EnumCategories([in] LCID lcid, 
       [out] IEnumCATEGORYINFO** ppeci);
// get description of a particular category
  HRESULT GetCategoryDesc([in] REFCATID rcatid, 
       [in] LCID lcid, 
        [out] OLECHAR ** ppszDesc);
// get list of classes compatible with specified categories
  HRESULT EnumClassesOfCategories(
       [in] ULONG cImplemented, (-1 indicates ignore)
       [in,size_is(cImplemented)] CATID rgcatidImpl[],
       [in] ULONG cRequired,    (-1 indicates ignore)
       [in,size_is(cRequired)] CATID rgcatidReq[],
       [out] IEnumCLSID** ppenumClsid);
// verify class is compatible with specified categories
  HRESULT IsClassOfCategories([in] REFCLSID rclsid, 
       [in] ULONG cImplemented,
       [in,size_is(cImplemented)] CATID rgcatidImpl[],
       [in] ULONG cRequired,
       [in,size_is(cRequired)] CATID rgcatidReq[]);
// get list of class's implemented categories
  HRESULT EnumImplCategoriesOfClass([in] REFCLSID rclsid,
       [out] IEnumCATID** ppenumCatid);
// get list of class's required categories
  HRESULT EnumReqCategoriesOfClass([in] REFCLSID rclsid, 
       [out] IEnumCATID** ppenumCatid);
}

Most of these methods return cursors to lists of category or class IDs. These cursors are called enumerators and are described in detail in Chapter 7.

The following code demonstrates how to extract the list of classes that are members of the Mammal category:

// get the standard category manager

ICatInformation *pci = 0;
HRESULT hr = CoCreateInstance( 
          CLSID_StdComponentCategoriesMgr, 0, 
          CLSCTX_ALL, IID_ICatInformation, (void**)&pci);
if (SUCCEEDED(hr)) {
// get the classes that are Simians (ignore required cat.s)
  IEnumCLSID *pec = 0;
  CATID rgcid[1];
  rgcid[0] = CATID_Simian;
  hr = pci->EnumClassesOfCategories(1, rgcid, -1, 0, &pec);
  if (SUCCEEDED(hr)) {
// walk list of CLSIDs 64 at a time
    enum { MAX = 64 };
    CLSID rgclsid[MAX];
    do {
      ULONG cActual = 0;
      hr = pec->Next(MAX, rgclsid, &cActual);
      if (SUCCEEDED(hr)) {
        for (ULONG i = 0; i < cActual; i++)
          DisplayClass(rgclsid[i]);
      }
    } while (hr == S_OK);
    pec->Release();
  }
  pci->Release();
}

This code fragment ignores the fact that the client program may not support the required categories of the resultant list of classes. Had the client been aware of its supported site categories, it could have specified the list of all supported categories.

Consider the following call to EnumClassesOfCategories:

CATID rgimpl[1]; rgimpl[0] = CATID_Simians;
CATID rgreq[3]; rgreq[0] = CATID_HasWater; 
rgreq[1] = CATID_HasOxygen; rgreq[2] = CATID_HasMilk;
hr =pci->EnumClassesOfCategories(1, rgimpl, 3, rgreq, &pec);

The resultant list of classes would contain all Simians that require no more than Oxygen, Water, and Milk from the client’s environment. In the case of the Chimp class registered previously, Chimp would be a compatible class, as it implements the specified category Simian and requires a subset of the specified categories used in the query.

One final aspect of component categories that bears discussion is the notion of a default class for a category. COM allows a CATID to be registered as a CLSID under

HKEY_CLASSES_ROOT\CLSID

To map a CATID to a default CLSID, the TreatAs facility introduced by emulation is used. To indicate that the Gorilla class is the default class of Simian, one would add the following registry key:

[HKCR\CLSID\{CATID_Simian}\TreatAs]
@={CLSID_Gorrila}

This simple convention allows clients simply to use CATIDs where CLSIDs are expected:

// create an instance of the default Simian class
hr = CoCreateInstance(CATID_Simian, 0, CLSCTX_ALL, 
                     IID_IApe, (void**)&pApe);

If no default class is registered for the specified category, the activation call will fail, returning REGDB_E_CLASSNOTREG.

soptest

Re: Inheritence & Virtual functions with COM/ATL

Vivek Rajan11-Jul-02 11:10

Vivek Rajan

11-Jul-02 11:10

Ed-

Can you post the class signature of the derived class (i.e its inheritance list ) as well as whether or not you have used ATL_NO_VTABLE ?

One place to look at is :

1. Do you have ExecuteService defined as one of the methods in the interface definition for IPObject ?

HTH -
Vivek

Re: Inheritence & Virtual functions with COM/ATL

Ed K11-Jul-02 15:42

Ed K

11-Jul-02 15:42

Thanks for offering to take a look at it. Rather than posting all the code here I've put it into a zip on my site to download.

test.zip

The zip contains 2 zip files. One is the test client and the other the servicefactory. I'm using VC6 and WTL7 (I'm in love with CString!).

ServiceFactory has a method GetService(BSTR name, IPObject**ppObj) which will get either the FoodService or the BeverageService depending on the string passed in. PObject has a virtual method ExecuteServie(BSTR param) which calls a virtual method Display. ExecuteService is only implemented in PObject. Display is only implemented in the subclasses.

If you step through the test client you can actually see that the right object is created however when I called ExecuteService it throws an unhandled exception.

Thanks again! Rose | [Rose]

Re: Inheritence & Virtual functions with COM/ATL

Vivek Rajan12-Jul-02 6:44

Vivek Rajan

12-Jul-02 6:44

Ed -

The problem is you are trying to call a ExecuteService using a IFoodService pointer. This would work if IFoodService were derived from IPObject, but it is not ! This means that the vtable entry for ExecuteService just does not exist for IFoodService. Typecasting it via reinterpret_cast wont fix it either.

I made the following change and it worked for me.

In File factory.cpp
Note that we now QI for IPObject instead of IFoodService

<br />
return	CComCreator< CComObject<CBeverageService> >::CreateInstance(NULL, IID_IPObject, reinterpret_cast<void**>(ppPObj) );<br />

This would ensure that the interface pointer for IPObject is returned instead of IFoodService.
If you really want IFoodService on the client, you can always QI for it from IPObject.

Suggested change
Change the interface map for CFood and CBev

<br />
BEGIN_COM_MAP(CFoodService)<br />
	COM_INTERFACE_ENTRY(IFoodService)<br />
	COM_INTERFACE_ENTRY_CHAIN(CPObject)<br />
END_COM_MAP()<br />

This is because CFoodService does not directly implement IPObject but rather uses the implementation already defined in a base class. The QI then searches for the implementation in the base class.

Hope that helps-
Vivek

Re: Inheritence & Virtual functions with COM/ATL

Ed K12-Jul-02 8:44

Ed K

12-Jul-02 8:44

What it comes down to is that I have to implement ExecuteService in each of the base classes to handle the initial request (Command Pattern) then let it call a template method in the parent class to get things moving as I want them to. I really don't want the client to have a clue as to what he is calling. That way I can add other base classes without having to recompile the client.

Thanks for checking it out. I really appreciate it!

ed

The nice thing about egotists is that they don't talk about other people.

Lucille Harper

How to use one instance of a COM object in different processes?

Jawid5-Jul-02 5:37

Jawid

5-Jul-02 5:37

Hi everyone,
I am not able to find a way how to use the only one (common) instance of my COM object from several processes. Here I see the only solution of multiple instances and that way I lose some of the pointers.
Can anybody guide me how to do that?

Thanks,

Jawid

Use Ctrl+Left/Right to switch messages, Ctrl+Up/Down to switch threads, Ctrl+Shift+Left/Right to switch pages.