Thread View: borland.public.cppbuilder.multimedia
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3 total messages
Started by Robert Penoyer
Wed, 28 Mar 2001 03:07
waveInOpen and CALLBACK
Author: Robert Penoyer
Date: Wed, 28 Mar 2001 03:07
Date: Wed, 28 Mar 2001 03:07
13 lines
1273 bytes
1273 bytes
I'm trying to learn to use waveInOpen. The fourth argument of this function, dwCallback, is an _address_ of a "fixed callback function, an event handle, or a handle of a window or thread." 1. How do I determine the address of a function or event handle? 2. What is a "fixed" function? 3. How do I get the handle of a window or thread? 4. How do I invoke the event that triggers an event callback? Such an event might be "buffer full." Thanks, Bob
Re: waveInOpen and CALLBACK
Author: Michael Warner
Date: Wed, 28 Mar 2001 17:13
Date: Wed, 28 Mar 2001 17:13
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On Tue, 27 Mar 2001 19:07:40 -0800, Robert Penoyer <rpenoyer@earthlink.net> wrote: >I'm trying to learn to use waveInOpen. The fourth argument of this >function, dwCallback, is an _address_ of a "fixed callback function, an >event handle, or a handle of a window or thread." > >1. How do I determine the address of a function or event handle? In C/C++ you just specify its name, with no parentheses or arguments. You may have to cast it to the correct type, which may be DWORD for a multi-function argument like that one. Yuck. >2. What is a "fixed" function? The term is a bit vague, but in practice it must be a standalone C-style function or a static class member. Normal class members can't be used as callbacks, since the "this" pointer isn't available to pass to them. >3. How do I get the handle of a window or thread? The handle of a VCL-created windows is obtained with form->Handle. Threads are normally specified by thread ID, so I'm not sure about that one. >4. How do I invoke the event that triggers an event callback? Such an >event might be "buffer full." Read up on events in the API help. The callback mechanism is the easiest to use of these.
Re: waveInOpen and CALLBACK
Author: Robert Penoyer
Date: Wed, 28 Mar 2001 20:07
Date: Wed, 28 Mar 2001 20:07
40 lines
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2289 bytes
Mike, Simple answers to perplexing questions are the best. Thanks! Bob Michael Warner wrote: > On Tue, 27 Mar 2001 19:07:40 -0800, Robert Penoyer > <rpenoyer@earthlink.net> wrote: > > >I'm trying to learn to use waveInOpen. The fourth argument of this > >function, dwCallback, is an _address_ of a "fixed callback function, an > >event handle, or a handle of a window or thread." > > > >1. How do I determine the address of a function or event handle? > > In C/C++ you just specify its name, with no parentheses or arguments. > You may have to cast it to the correct type, which may be DWORD for > a multi-function argument like that one. Yuck. > > >2. What is a "fixed" function? > > The term is a bit vague, but in practice it must be a standalone > C-style function or a static class member. Normal class members can't > be used as callbacks, since the "this" pointer isn't available to pass > to them. > > >3. How do I get the handle of a window or thread? > > The handle of a VCL-created windows is obtained with form->Handle. > Threads are normally specified by thread ID, so I'm not sure about > that one. > > >4. How do I invoke the event that triggers an event callback? Such an > >event might be "buffer full." > > Read up on events in the API help. > > The callback mechanism is the easiest to use of these.
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