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Groups > comp.lang.c++ > #87065

Re: calling a Event Handler within a class

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Am 17.10.2022 um 22:51 schrieb Jens:
> Hello,
> I have a hard coded TSpeedButton on TForm.
> I would like to assign it a OnClick Event Handler in a procedureal
> global function (not a member of a class).
> How can I do this ?
> 
> Thanks for ideas.

Have a lambda wich you can cast to a normal function pointer and
access local variables of the function by declaring them as either
static or thread_local depending on if the function needs to be
thread-safe. If you have some captures with that function pointer
this approach doesn't work since you can't cast lambdas with cap-
tures to normal function pointers.

Here's an example how to do this from another context:

a#include <iostream>
#include <vector>
#include <string>
#include <climits>
#include <link.h>
#include <dlfcn.h>

using namespace std;

int main()
{
	thread_local vector<string> images;
	dl_iterate_phdr(
		[]( dl_phdr_info* image, size_t size, void* pFn ) -> int
		{
			try
			{
				if( *image->dlpi_name )
					images.emplace_back( image->dlpi_name );
				else
				{
					Dl_info dlInfo;
					if( !dladdr( (void*)image->dlpi_addr, &dlInfo ) )
						return 1;
					char exePath[PATH_MAX];
					if( !realpath( dlInfo.dli_fname, exePath ) )
						return 1;
					images.emplace_back( exePath );
				}
				return 0;
			}
			catch (...)
			{
				return 1;
			}
			return 1;
		}, nullptr );
	for( string const &image : images )
		cout << "\"" << image << "\"" << endl;
}

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calling a Event Handler within a class Jens <paule32.jk@gmail.com> - 2022-10-17 22:51 +0200
  Re: calling a Event Handler within a class Frederick Virchanza Gotham <cauldwell.thomas@gmail.com> - 2022-10-17 14:32 -0700
  Re: calling a Event Handler within a class Juha Nieminen <nospam@thanks.invalid> - 2022-10-18 07:06 +0000
    Re: calling a Event Handler within a class Jens <paule32.jk@gmail.com> - 2022-10-18 10:06 +0200
      Re: calling a Event Handler within a class Juha Nieminen <nospam@thanks.invalid> - 2022-10-18 09:27 +0000
        Re: calling a Event Handler within a class JiiPee <kerrttuPoistaTama11@gmail.com> - 2022-10-20 18:36 +0300
      Re: calling a Event Handler within a class David Brown <david.brown@hesbynett.no> - 2022-10-18 11:45 +0200
      Re: calling a Event Handler within a class Manfred <noname@add.invalid> - 2022-10-19 02:43 +0200
  Re: calling a Event Handler within a class Bonita Montero <Bonita.Montero@gmail.com> - 2022-10-18 14:21 +0200
  Re: calling a Event Handler within a class Jens <paule32.jk@gmail.com> - 2022-10-19 12:58 +0200
  Re: calling a Event Handler within a class Lynn McGuire <lynnmcguire5@gmail.com> - 2022-10-20 00:25 -0500

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