xlib XNextEvent checking if a key is held down - c++

Question

I am using xlib to get keyboard input I want to simulate windows its getAsynckeystate() to check if a button is being pressed I tried using a timer to fix the result but its still broken. the function should always return true if 'z' is held down even if other keys are pressed or released at the same time (not working right now)
Code below
bool KeyboardState::keyPressed(Display* d, Window curFocus,int revert, Window root) {
XEvent ev;
XNextEvent(d, &ev);
clock_t startTime;
switch (ev.type) {
case FocusOut:
if (curFocus != root)
XSelectInput(d, curFocus, 0);
XGetInputFocus(d, &curFocus, &revert);
printf("New focus is %d\n", (int) curFocus);
if (curFocus == PointerRoot)
curFocus = root;
XSelectInput(d, curFocus, KeyReleaseMask | FocusChangeMask | KeyPressMask);
break;
case KeyPress:
ks = XLookupKeysym(&(ev.xkey), 0);
if (ks == XK_z) {
keyState = true;
startTime = clock();
}
break;
case KeyRelease:
if(ks == XK_z && startTime - clock() > 0){
ks = XLookupKeysym(&(ev.xkey), 0);
keyState = false;
}
}
return keyState;
}

Answer 1

n.m linked following function which is accepted as answer:
tronche.com/gui/x/xlib/input/XQueryKeymap.html

Answer 2

I wrote the following code snippet to help do keyboard shortcuts with multiple non-modifier keys e.g. super + up + right.
#include <X11/Xlib.h>
// Returns 0 if key is not down;
// A non-zero integer if it is down.
// targetString should be appropriate for XStringToKeysym.
int is_down(Display *dis, char *targetString)
{
char keys_return[32] = {0};
KeySym targetSym = XStringToKeysym(targetString);
KeyCode targetCode = XKeysymToKeycode(dis, targetSym);
int targetByte = targetCode / 8;
int targetBit = targetCode % 8;
int targetMask = 0x01 << targetBit;
XQueryKeymap(dis, keys_return);
return keys_return[targetByte] & targetMask;
}
I've posted a more complete example with compilation instructions on GitHub. You can find a complete list of key names in a file named X11/keysymdef.h; on my Arch computer it was at /usr/include/X11/keysymdef.h. I also found an example on the web as the second Google result for x11 keysymdef.