Re: Use nested functions as callbacks with Windows API functions?
On Monday, 1 October 2018 at 20:27:43 UTC, spikespaz wrote:
Of course there is nothing wrong with defining each callback as
a separate function, but then comes the issue of naming them. I
also don't like the way it makes my code look.
I think the best you can do is something like this:
---
auto callback(T, string file = __FILE__, size_t line =
__LINE__)(T handler) {
import std.traits;
__gshared T handler_;
handler_ = handler;
extern(Windows)
ReturnType!T fn(Parameters!T args) {
synchronized return handler_(args);
}
return
}
void main() {
HWND[] list;
EnumWindows((HWND hwnd, LPARAM lparam) {
list ~= hwnd;
return TRUE;
}.callback(), 0);
writeln(list);
}
---
Re: Use nested functions as callbacks with Windows API functions?
On Monday, 1 October 2018 at 23:07:29 UTC, spikespaz wrote: The problem with the code you have is that the callback needs to be extern (Windows). I don't know how to do that with a "lambda". Neither do I actually. Apparently it is impossible. Best I could squeeze out was this: https://run.dlang.io/is/CpyfW3
Re: Use nested functions as callbacks with Windows API functions?
On Monday, 1 October 2018 at 21:03:24 UTC, Boris-Barboris wrote:
On Monday, 1 October 2018 at 20:27:43 UTC, spikespaz wrote:
I was hoping I could use something more akin to JavaScript's
syntax: (void* hWnd, long) => {}.
I tried this but I'm getting errors with the signature, it
says the function is a delegate and apparently Windows API
can't accept a delegate.
You can make it a non-delegate by passing a pointer to hWndList
in lParams as it was supposed to by WinApi devs, instead of
zero, and not implicitly capturing stack pointer by referencing
hWndList directly from the body.
https://run.dlang.io/is/t4k4Nc
The problem with the code you have is that the callback needs to
be extern (Windows). I don't know how to do that with a "lambda".
===
import core.sys.windows.windows: EnumWindows;
import std.stdio: writeln;
void main() {
void*[] hWndList;
EnumWindows((void* hWnd, void* lParam) nothrow {
*(cast(void*[] *) lParam) ~= hWnd;
return true;
}, );
writeln(hWndList);
}
===
source\cb.d(7): Error: function
core.sys.windows.winuser.EnumWindows(extern (Windows) int
function(void*, long) nothrow, long) is not callable using
argument types (bool function(void* hWnd, void* lParam) pure
nothrow @system, void*[]*)
source\cb.d(7):cannot pass argument __lambda1 of type
bool function(void* hWnd, void* lParam) pure
nothrow @system to parameter extern (Windows) int function(void*,
long) nothrow
Re: Use nested functions as callbacks with Windows API functions?
On Monday, 1 October 2018 at 21:03:24 UTC, Boris-Barboris wrote:
On Monday, 1 October 2018 at 20:27:43 UTC, spikespaz wrote:
I was hoping I could use something more akin to JavaScript's
syntax: (void* hWnd, long) => {}.
I tried this but I'm getting errors with the signature, it
says the function is a delegate and apparently Windows API
can't accept a delegate.
You can make it a non-delegate by passing a pointer to hWndList
in lParams as it was supposed to by WinApi devs, instead of
zero, and not implicitly capturing stack pointer by referencing
hWndList directly from the body.
https://run.dlang.io/is/t4k4Nc
I don't know how to do this. I'm not the best with pointers, I'm
still learning D and I'm unfamiliar with functional programming.
==
import core.sys.windows.windows: EnumWindows;
import std.stdio: writeln;
extern (Windows) int callback(void* hWnd, long hWndList) nothrow {
hWndList ~= hWnd;
return true;
}
void main() {
void*[] hWndList;
EnumWindows(, );
writeln(hWndList);
}
==
Clearly I can't use to pass the reference, how would I
access the variable by the memory address inside the callback?
Re: Use nested functions as callbacks with Windows API functions?
On Monday, 1 October 2018 at 20:27:43 UTC, spikespaz wrote:
I was hoping I could use something more akin to JavaScript's
syntax: (void* hWnd, long) => {}.
I tried this but I'm getting errors with the signature, it says
the function is a delegate and apparently Windows API can't
accept a delegate.
You can make it a non-delegate by passing a pointer to hWndList
in lParams as it was supposed to by WinApi devs, instead of zero,
and not implicitly capturing stack pointer by referencing
hWndList directly from the body.
https://run.dlang.io/is/t4k4Nc
Use nested functions as callbacks with Windows API functions?
I have the following code, this works.
import core.sys.windows.windows: EnumWindows;
import std.stdio: writeln;
void*[] hWndList;
extern (Windows) int callback(void* hWnd, long /* lParams */ )
nothrow {
hWndList ~= hWnd;
return true;
}
void main() {
EnumWindows(, 0);
writeln(hWndList);
}
I was hoping I could use something more akin to JavaScript's
syntax: (void* hWnd, long) => {}.
I tried this but I'm getting errors with the signature, it says
the function is a delegate and apparently Windows API can't
accept a delegate.
import core.sys.windows.windows: EnumWindows;
import std.stdio: writeln;
void main() {
void*[] hWndList;
EnumWindows((void* hWnd, long /* lParams */ ) nothrow {
hWndList ~= hWnd; return true;
}, 0);
writeln(hWndList);
}
I'm not going to even paste the compiler error because I am very
clearly going about this the wrong way.
Of course there is nothing wrong with defining each callback as a
separate function, but then comes the issue of naming them. I
also don't like the way it makes my code look.
Thanks.
