c++ win32 get system volume accelerator

Question

is it possible to detect which keys are used for a system volume accelerator in win32 using c++? For example: if the user presses fn + key up (and this is also the key combination to change the system volume), i would like to detect this event and response to it.

Related to https://stackoverflow.com/q/22975916/2877364 – cxw Dec 04 '18 at 14:22 — cxw, Dec 04 '18 at 14:22

Hans Passant · Accepted Answer · 2011-10-01T14:06:47.277

3

This is handled by the machine's BIOS. It produces a keystroke, VK_VOLUME_DOWN or VK_VOLUME_UP virtual key. DefWindowProc handling of that WM_KEYDOWN message produces WM_APPCOMMAND, APPCOMMAND_VOLUME_UP/DOWN. DefWindowProc handling of that message adjusts the volume.

edited Oct 01 '11 at 14:06

answered Oct 01 '11 at 12:35

Hans Passant

922,412
146
1,693
2,536

Actually, `DefWindowProc` handling of that message forwards `WM_APPCOMMAND` to Explorer, and Explorer adjusts the volume. If you want to override the volume buttons in your app, respond to the `WM_APPCOMMAND` message. – Raymond Chen Oct 01 '11 at 14:10
@Raymond - aren't you going too fast? DefWindowProc handling of WM_APPCOMMAND on a toplevel window invokes the shell hook afaik. If WM_KEYDOWN handling sends WM_APPCOMMAND straight to Explorer then there's no way to respond to it. – Hans Passant Oct 01 '11 at 14:22
Yeah, the `WM_APPCOMMAND` goes to Explorer via a shell hook. The point was that it's Explorer that changes the volume, not `DefWindowProc`. The distinction is not significant to this question, but it affects similar questions. – Raymond Chen Oct 01 '11 at 17:06
but the messages WM_APPCOMMAND and WM_KEYDOWN are sent only when the application has focus. How can i detect this keys even if the application doesn't have focus? – blejzz Oct 12 '11 at 10:34

score 0 · Answer 2 · answered Oct 01 '11 at 12:26

I don't think this is possible generally. The fn-keys are usually handled by the BIOS-SMM-ACPI whatever, and that is not accesible to user programs.

Maybe, if it were translated to the standard multimedia volume-up key, you could get that, but I wouldn't bet on it.

score 0 · Answer 3 · answered Oct 01 '11 at 12:32

0

see this post... http://www.rohitab.com/discuss/topic/21252-change-volume/

answered Oct 01 '11 at 12:32

YAHOOOOO

939
4
19
27

The OP is asked how to detect keypresses that lead to system volume changes, not how to modify the system volume. – In silico Oct 01 '11 at 12:36

c++ win32 get system volume accelerator

3 Answers3