How to get macOS keyboard shortcuts set in System Preferences programmatically? - c++

Question

On macOS the key combination CMD+Backtick is used to cycle through the open windows of an application when using an english keyboard. On German keyboards for example the combination is CMD+<. This shortcut can even be configured using System Preferences -> Keyboard -> Shortcuts -> Keyboard -> Move focus to next window.
For my multi-window GUI application using FLTK I want to utilize this shortcut, but have no idea how to fetch the combination the user has set on his or her system. So what I'm looking for is a macOS system call that gives me the key combination that is used to Move focus to next window on this very Mac.
Of course if there would be a somewhat builtin way using FLTK I'd prefer that over having to use native system calls.
Googling for this issue is a nightmare ...
Update 08/10/2017
Öö's answer gave me some ideas for additional research. I've since learned that the preferences are stored in com.apple.symbolichotkeys, more precisely in key 27.
27 = {
enabled = 1;
value = {
parameters = (
98,
11,
524288
);
type = standard;
};
};
Parameter 1 (98): That's the ASCII code for "b". The first parameter has the ascii code of the shortcut used or 65535 if it's a non-ascii character.
Parameter 2 (11): That's the keyboard code for the kVK_ANSI_B (source). These codes are keyboard dependent. On a US keyboard, kVK_ANSI_Z is 0x06, while on a german keyboard it's 0x10.
Parameter 3 (524288): That's for the modifier key:
0x000000 => "No modifier",
0x020000 => "Shift",
0x040000 => "Control",
0x080000 => "Option",
0x100000 => "Command",
(0x80000 equals 524288.)
So my task just seems to be to parse the output of defaults read com.apple.symbolichotkeys, get the key combinations from the parameter dictionary, interpret those combinations correctly depending on the keyboard layout and use these information to set the callbacks in my FLTK app.

Answer 1

I can't test right now the answer ... but I would first try to popen the defaults command like:
HFILE file;
if (!(file = popen("defaults read NSGlobalDomain NSUserKeyEquivalents", "r")))
{
return nullptr;
}
const int MAX_BUF_SIZE = 512;
char temp[MAX_BUF_SIZE+1] = "";
while (fgets(temp, MAX_BUF_SIZE, file) > 0)
{
printf("%s",temp);
memset(temp, 0, MAX_BUF_SIZE+1);
}
pclose(file);
Here I just printf its output but you will likely want to parse it.