BorlandTalk.com Borland discussion newsgroups   Archives   FAQ   Search   Memberlist   Usergroups   Register   Profile   Log in to check your private messages   Log in  TimeSetEvent          BorlandTalk.com Forum Index -> C++ Builder (Native API) View previous topic :: View next topic   Author Message David Dean Guest Posted: Fri Apr 28, 2006 5:03 pm    Post subject: TimeSetEvent I'm having trouble using the TimeSetEvent API call. The following source fails to compile: //----------------------------------------------------------------------- #include <vcl.h> #pragma hdrstop //----------------------------------------------------------------------- #pragma package(smart_init) class myClass { public: void send(AnsiString outString, int delay, unsigned short timeout); void CALLBACK OneShotTimer(UINT wTimerID, UINT msg, DWORD dwUser, DWORD dw1, DWORD dw2); }; void myClass::send(AnsiString outString, int delay, unsigned short timeout) { timeSetEvent(timeout, 100, (LPTIMECALLBACK)&OneShotTimer, NULL, TIME_ONESHOT); } //----------------------------------------------------------------------- void CALLBACK myclass::OneShotTimer(UINT wTimerID, UINT msg, DWORD dwUser, DWORD dw1, DWORD dw2) { } //----------------------------------------------------------------------- I know there are pieces missing, but can someone get me on the right track? I'm sure it is an obvious mistake, but I've looked at it to long. The error produced by the compiler is: [C++ Error] Unit1.cpp(22): E2031 Cannot cast from 'void (__stdcall * (_closure )(unsigned int,unsigned int,unsigned long,unsigned long,unsigned long))(unsigned int,unsigned int,unsigned long,unsigned long,unsigned long)' to 'void (__stdcall *)(unsigned int,unsigned int,unsigned long,unsigned long,unsigned long)' -David -- -David Nihil curo de ista tua stulta superstitione. Back to top David Dean Guest Posted: Fri Apr 28, 2006 6:03 pm    Post subject: Re: TimeSetEvent In article <44524b44$1 (AT) newsgroups (DOT) borland.com>, "Remy Lebeau \(TeamB\)" <no.spam (AT) no (DOT) spam.com> wrote: Quote: For example: Excellent example. Thank you. I had a feeling that the solution was something along those lines, but my mind went blank. -- -David Nihil curo de ista tua stulta superstitione. Back to top David Dean Guest Posted: Fri Apr 28, 2006 6:03 pm    Post subject: Re: TimeSetEvent In article <32i4521k20p3ha1bq744jvbfteei2kr01q (AT) 4ax (DOT) com>, Bob Gonder <notbg (AT) notmindspring (DOT) invalid> wrote: Quote: Asked many times on this very group. You might Google for "nativeapi _closure" Thanks Bob. It should have been obvious to google those terms, but I must have been looking at it too long to think straight. Remy's example was exactly the jog I needed for my memory. -- -David Nihil curo de ista tua stulta superstitione. Back to top Bob Gonder Guest Posted: Fri Apr 28, 2006 6:03 pm    Post subject: Re: TimeSetEvent David Dean wrote: Quote: class myClass { void CALLBACK OneShotTimer(UINT wTimerID, UINT msg, DWORD dwUser, }; timeSetEvent(timeout, 100, (LPTIMECALLBACK)&OneShotTimer, NULL, TIME_ONESHOT); [C++ Error] Unit1.cpp(22): E2031 Cannot cast from 'void (__stdcall * (_closure )(unsigned int,unsigned int,unsigned long,unsigned Asked many times on this very group. You might Google for "nativeapi _closure" Bottom line is callbacks must be static or else non-members. Back to top Remy Lebeau (TeamB) Guest Posted: Fri Apr 28, 2006 6:03 pm    Post subject: Re: TimeSetEvent "David Dean" <ozchzhq02 (AT) sneakemail (DOT) com> wrote in message news:ozchzhq02-9725F7.12284128042006 (AT) frylock (DOT) local... Quote: The error produced by the compiler is: You are trying to use a non-static class method as the callback. You cannot do that (not directly, anyway). Such a method requires a 'this' pointer be passed to it when called. TimeSetEvent() does not know how to do that. It expects a standalone function as the callback. In order to use a class method, you must declare it as 'static'. The only downside is that the callback will no longer be able to access non-static members of the class, since no 'this' pointer is available. Fortunately, TimeSetEvent() allows you to specify your own 32-bit value in the dwUser parameter, and that value will be passed to the callback. So you can pass the class's 'this' pointer in that parameter. For example: class myClass { private: int value; // <-- for deomstration only static void CALLBACK OneShotTimer(UINT wTimerID, UINT msg, DWORD dwUser, DWORD dw1, DWORD dw2); public: void send(const AnsiString &outString, int delay, unsigned short timeout); }; void myClass::send(const AnsiString &outString, int delay, unsigned short timeout) { //... value = 0; timeSetEvent(timeout, 100, &OneShotTimer, reinterpret_cast<DWORD>(this), TIME_ONESHOT); } void CALLBACK myClass::OneShotTimer(UINT wTimerID, UINT msg, DWORD dwUser, DWORD dw1, DWORD dw2) { myClass *pThis = reinterpret_cast<myClass*>(dwUser); // use pThis as needed ... pThis->value = 1; } Gambit Back to top Remy Lebeau (TeamB) Guest Posted: Fri Apr 28, 2006 8:03 pm    Post subject: Re: TimeSetEvent "Bob Gonder" <notbg (AT) notmindspring (DOT) invalid> wrote in message news:32i4521k20p3ha1bq744jvbfteei2kr01q (AT) 4ax (DOT) com... Quote: Bottom line is callbacks must be static or else non-members. There is a third option, though not very straight forward - use a proxy. That is what the VCL does to allow non-static class methods to be used as Win32 API window procedure callbacks. Basically, for each desired method for each class instance, you allocate a block of executable memory that contains a stub function along with the class instance's 'this' pointer and desired method pointer. Then you can pass the memory block whereever a non-member callback is expected. When the API calls the callback, the stub function is executed automatically, which then decodes the parameters from the call stack and reformats the call stack to place the 'this' pointer onto the stack, and then jumps into the class method. As far as the class method's inner code is concerned, it will act exactly as if it had been called directly by the API without a proxy. It is a very effective technique, albeit not a trivial one to implement since you have to use low-level assembly code for the stub function. If you have the VCL source code installed, you can look at the code for the MakeObjectInstance() function for an example. Gambit Back to top Bruce Salzman Guest Posted: Fri Apr 28, 2006 8:03 pm    Post subject: Re: TimeSetEvent "Remy Lebeau (TeamB)" <no.spam (AT) no (DOT) spam.com> wrote in message news:445265cc$1 (AT) newsgroups (DOT) borland.com... Quote: "There is a third option, though not very straight forward - use a proxy. <snip> ....not a trivial one to implement since you have to use low-level assembly code for the stub function." see "Kludge" ;^) -- Bruce Back to top Remy Lebeau (TeamB) Guest Posted: Fri Apr 28, 2006 11:03 pm    Post subject: Re: TimeSetEvent " Bruce Salzman" <bruce (AT) nospam (DOT) org> wrote in message news:44526fbb (AT) newsgroups (DOT) borland.com... Quote: see "Kludge" Not a kluge. It is a very powerful alternative when a callback does not allow user-defined values and you don't want to use global pointers. Gambit Back to top Bruce Salzman Guest Posted: Fri Apr 28, 2006 11:03 pm    Post subject: Re: TimeSetEvent "Remy Lebeau (TeamB)" <no.spam (AT) no (DOT) spam.com> wrote in message news:44528e06 (AT) newsgroups (DOT) borland.com... Quote: " Bruce Salzman" <bruce (AT) nospam (DOT) org> wrote in message news:44526fbb (AT) newsgroups (DOT) borland.com... see "Kludge" Not a kluge. It is a very powerful alternative when a callback does not allow user-defined values and you don't want to use global pointers. One man's kludge is another man's powerful alternative, I guess. It's one thing for a compiler/library vendor to do this kind of thing, with (presumably) full knowlege of the pitfalls. It's quite another to put it in your own application. I would hate to be the next (or next, or...) programmer hired to maintain something like this, regardless of how elegent it is in theory. Just my two cents. -- Bruce Back to top Display posts from previous: All Posts1 Day7 Days2 Weeks1 Month3 Months6 Months1 Year Oldest FirstNewest First         BorlandTalk.com Forum Index -> C++ Builder (Native API) All times are GMT Page 1 of 1   Jump to: Select a forum C++ Builder Newsgroups----------------C++ BuilderC++ Builder (ActiveX)C++ Builder (Announcements)C++ Builder (Command Line Tools)C++ Builder DatabasesC++ Builder Databases (ADO)C++ Builder Databases (Desktop)C++ Builder Databases (InterBase Express)C++ Builder Databases (Multi-Tier)C++ Builder Databases (SQL Servers)C++ Builder (Graphics)C++ Builder (IDE)C++ Builder (Internet)C++ Builder (Internet Socket)C++ Builder (Internet Web)C++ Builder (Jobs)C++ Builder (Language)C++ Builder (Language C++)C++ Builder (Compatibility with MFC)C++ Builder (Native API)C++ Builder (Non-Technical)C++ Builder (Students)C++ Builder (Third Party Tools)C++ Builder (Upgrade)C++ Builder (VCL)C++ Builder (VCL Components Usage)C++ Builder (VCL Components Development)C++ Builder (VCL Usage)C++ Builder (WinAPI)C++ Builder Installation Delphi Newsgroups----------------Delphi (General)Delphi ActiveX Controls UsageDelphi ActiveX Controls DevelopmentDelphi As400Delphi DatabasesDelphi Databases (ADO)Delphi Databases (dbExpress)Delphi Databases (Desktop)Delphi Databases (InterBase Express)Delphi Databases (Multi-Tier)Delphi Databases (SQL Servers)Delphi DeploymentDelphi GraphicsDelphi IDEDelphi InternationalizationDelphi InternetDelphi Internet Isapi-WebBrokerDelphi Internet WebSnapDelphi Internet WinsockDelphi JobsDelphi Language BASMDelphi Language ObjectPascalDelphi Model Driven Architecture (General)Delphi Model Driven Architecture (Third Party)Delphi MultimediaDelphi Native APIDelphi Non-TechnicalDelphi ObjectPascalDelphi OLE AutomationDelphi OO designDelphi OpenToolsAPIDelphi Reporting-ChartingDelphi RTLDelphi StudentsDelphi TeamSourceDelphi Thirdparty ToolsDelphi Thirdparty Tools (General)Delphi Thirdparty Tools (IntraWeb)Delphi Thirdparty Tools (RaveReports)Delphi UpgradeDelphi VCLDelphi VCL ComponentsDelphi VCL Components UsingDelphi VCL Components WritingDelphi WebServices SOAPDelphi WinAPIDelphi XMLDelphi Installationcomp.lang.pascal.delphi.components.misccomp.lang.pascal.delphi.components.usagecomp.lang.pascal.delphi.components.writingcomp.lang.pascal.delphi.databasescomp.lang.pascal.delphi.misccomp.sources.delphi JBuilder Newsgroups----------------JBuilderJBuilder AnnouncementsJBuilder Applet IssuesJBuilder As400JBuilder CompilerJBuilder CORBA/RMIJBuilder DatabasesJBuilder DB SwingJBuilder DebuggerJBuilder DeploymentJBuilder DocumentationJBuilder EnterpriseJBuilder HandheldJBuilder IDEJBuilder JavaJBuilder JavaAPIJBuilder Java LanguageJBuilder Java SwingJBuilder Java BeansJBuilder Java Beans UsageJBuilder Java Beans DevelopmentJBuilder JBCLJBuilder JDataStoreJBuilder JobsJBuilder LinuxJBuilder MacintoshJBuilder & MobileSetJBuilder MultiLingual AppsJBuilder Non-TechnicalJBuilder OpenToolsJBuilder Servlets (JSP)JBuilder StudentsJBuilder Team DevelopmentJBuilder Thirdparty ToolsJBuilder UpgradeJBuilder Installation InterBase Newsgroups----------------InterBaseInterBase Bug DiscussionInterBase GeneralInterBase IBConsoleInterBase OpenSourceInterBase ReplicationInterBase SQLInterBase ThirdpartyInterBase Installation Miscellaneous Borland Newsgroups----------------AppCenterAppServerEnteraVisiBroker  You cannot post new topics in this forum You cannot reply to topics in this forum You cannot edit your posts in this forum You cannot delete your posts in this forum You cannot vote in polls in this forum Powered by phpBB © 2001, 2006 phpBB Group SEO toolkit © 2004-2006 webmedic.