X11 dead_key problem

Linux
1

On MS-Windows when i type certain special characters (i.e., ~ ’ ") followed by a, o n I get á ó or ñ .
On Linux Debian, when I type these characters followed by a letter that doesn’t match.

I look inside juce_windows_X11_Windowing.cpp with no special code for Xlib dead key.
i suggest this draft code for case ê :

    if (utf8[0] != 0 || ((sym & 0xff00) == 0 && sym >= 8))
        keyPressed = true;

    if (sym == XK_dead_circumflex && flagcircum == false)
    {
        keyPressed = false;
        sym = 0x0000;
        flagcircum =true;
    }

    if (flagcircum &&  sym != 0x0000)
    {
       switch(sym)
       {
           case XK_a :
                unicodeChar = XK_acircumflex;
                keyPressed = true;
                flagcircum = false;
                break;
           case XK_e :
                unicodeChar = XK_ecircumflex;
                keyPressed = true;
                flagcircum = false;
                break;
            case XK_i :
                unicodeChar = XK_icircumflex;
                keyPressed = true;
                flagcircum = false;
                break;
             case XK_o :
                unicodeChar = XK_ocircumflex;
                keyPressed = true;
                flagcircum = false;
                break;
            case XK_u :
                unicodeChar = XK_ucircumflex;
                keyPressed = true;
                flagcircum = false;
                break;

            case XK_dead_circumflex :
                keyPressed = true;
                flagcircum = false;
                break;
        }

    }

    if (oldMods != currentModifiers)
        handleModifierKeysChange();

    if (keyDownChange)
        handleKeyUpOrDown (true);

    if (keyPressed)
        handleKeyPress (keyCode, unicodeChar);
}

it’s missing other symbols.

i don’t know if the problem is locale setting ?
if not, which is the way , use a library as xkbcommon ?

2

Surely this should be abstracted away by the OS somehow.

3

With xev no problem.

to be sure, i try this ample code from Alex Baines - Layout independent keys with Linux & X11
it’s ok.
the author note

If you want text input as well then use Xutf8LookupString which gives you the correct KeySym as well as correct unicode text, accounting for dead keys, compose keys and other complexities

#include <stdio.h>
#include <locale.h>
#include <X11/Xlib.h>
#include <X11/Xutil.h>
#include <X11/keysym.h>

int main(void){

setlocale(LC_ALL, "");

Display* dpy = XOpenDisplay(NULL);

Window win = XCreateSimpleWindow(dpy, DefaultRootWindow(dpy), 0, 0, 100, 100, 0, 0, 0);
XMapRaised(dpy, win);
XSync(dpy, False);
XComposeStatus state;

// X input method setup, only strictly necessary for intl key text

// loads the XMODIFIERS environment variable to see what IME to use
XSetLocaleModifiers("");

XIM xim = XOpenIM(dpy, 0, 0, 0);
if(!xim){
    // fallback to internal input method
    XSetLocaleModifiers("@im=none");
    xim = XOpenIM(dpy, 0, 0, 0);
}

// X input context, you can have multiple for text boxes etc, but having a
// single one is the easiest.

XIC xic = XCreateIC(xim,
                    XNInputStyle,   XIMPreeditNothing | XIMStatusNothing,
                    XNClientWindow, win,
                    XNFocusWindow,  win,
                    NULL);

XSetICFocus(xic);

// we want key presses

XSelectInput(dpy, win, KeyPressMask | KeyReleaseMask);

// main loop

XEvent prev_ev = {}, ev = {};

// you probably want XPending(dpy) here instead of 1, and an outer main loop
// where you do things other than just getting X events
while(1){
    XNextEvent(dpy, &ev);

    // this is needed for IMEs to hook keypresses is some cases,
    // if you need keys even when they're filtered things get a bit more complex

    if(XFilterEvent(&ev, None) == True) continue;

    switch(ev.type){
        case KeyPress: {

            // note: if you just want the XK_ keysym, then you can just use
            // XLookupKeysym(&ev.xkey, 0);
            // and ignore all the XIM / XIC / status etc stuff

            Status status;
            KeySym keysym = NoSymbol;
            char text[32] = {};

            // if you want to tell if this was a repeated key, this trick seems reliable.
            int is_repeat = prev_ev.type         == KeyRelease &&
                            prev_ev.xkey.time    == ev.xkey.time &&
                            prev_ev.xkey.keycode == ev.xkey.keycode;

            // you might want to remove the control modifier, since it makes stuff return control codes
            ev.xkey.state &= ~ControlMask;

            // get text from the key.
            // it could be multiple characters in the case an IME is used.
            // if you only care about latin-1 input, you can use XLookupString instead
            // and skip all the XIM / XIC setup stuff

            Xutf8LookupString(xic, &ev.xkey, text, sizeof(text) - 1, &keysym, &status);
            //XLookupString (&ev.xkey, text, sizeof (text), &keysym, &state);

            if(status == XBufferOverflow){
                // an IME was probably used, and wants to commit more than 32 chars.
                // ignore this fairly unlikely case for now
            }

            if(status == XLookupChars){
                // some characters were returned without an associated key,
                // again probably the result of an IME
                printf("Got chars: (%s)\n", text);
            }

            if(status == XLookupBoth){
                // we got one or more characters with an associated keysym
                // (all the keysyms are listed in /usr/include/X11/keysymdef.h)

                char* sym_name = XKeysymToString(keysym);
                printf("Got both: (%s), (%s)\n", text, sym_name);
            }

            if(status == XLookupKeySym){
                // a key without text on it
                char* sym_name = XKeysymToString(keysym);
                printf("Got keysym: (%s)\n", sym_name);
            }

            // example of responding to a key
            if(keysym == XK_Escape){
                puts("Exiting because escape was pressed.");
                return 0;
            }

        } break;
    }

    prev_ev = ev;
}

return 0;

}

4

Yes it is OS,and sometimes software particularities. on Debian 10 dead keys is enabled, with alt gr combining eg alt gr"o give ö . There is also the option to use compose compose"o for ö (this is what I use), of Alt non-combining then alt gro may produce ö or ó or . Experiment with the various settings for keyboard layout as for alt gr $ give ê a alt gre give €.
For memory…