🚀 go-pugleaf

Great that you worked it out.  Here's a link to an article that discusses
callback functions with C++, API and VCL events.

http://bcbjournal.org/articles/vol4/0007/Understanding_function_pointers.htm


"Angus" <aguspickton@yahoo.com> wrote in message
news:41b7d5c0@newsgroups.borland.com...
> No matter how many times i read about callback functions, i could never
> really grasp them. It often depends on the information is presented. With
> respect to callbacks, a little light flickered on, and here is an
> explanation for anyone dense as hardwood like myself. - and if you don't
> like it, oh well.
>
> Callback - the passing of your own function as a parameter into another
> function. Consider the call.
>
> void __fastcall TForm1::Button1Click(TObject *Sender){
>     std::auto_ptr<TComboBox>CB(new TComboBox(this));
>     SomeFunction( MyFunc, CB);
> }
>
> Now SomeFunction may be something you have written to retrieve a list of
all
> say all process names.. ie.
>
> BOOL WINAPI SomeFunction(PROCENUMPROC myfunc, LPARAM lParam){
>    // ...some code..e.g getting a the next process in a snapshot list.
now
> call your own function MyFunc.e.g.
>
>   while(MyFunc(processname, lParam) && ProcessesRemain){
>          //pass in a var from this func, AND a var from your calling vcl
> program
>         if(dada)
>            ProcessesRemain = false;
>   }
> }
>
> ...and MyFunc...
> BOOL CALLBACK MyFunc(char*  processname, LPARAM lParam){
>    TComboBox* cb = (TComboBox*)lParam; //do a cast
>     cb->Items->Add(AnsiString(processname));
>     return true;
> }
>
> In essence then, MyFunc is passed into SomeAPICallbackFunction. In this
> example, each process is iterated using snapshot.
> With each process found, a call to MyFunc is made, passing in the name of
> the process.. and in this instance a link to your calling program, a combo
> box.
>
> rgds Angus.
>
>