Get status of currently active modifiers in X11

user_3560981 0
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Is there a way to get informations on current active modifiers in X? E.g. if Capslock is active, if shift is pressed, etc.

According to the xkbcommon-keysyms.h this is a list of all X11 modifiers:

#define XKB_KEY_Shift_L                       0xffe1  /* Left shift */
#define XKB_KEY_Shift_R                       0xffe2  /* Right shift */
#define XKB_KEY_Control_L                     0xffe3  /* Left control */
#define XKB_KEY_Control_R                     0xffe4  /* Right control */
#define XKB_KEY_Caps_Lock                     0xffe5  /* Caps lock */
#define XKB_KEY_Shift_Lock                    0xffe6  /* Shift lock */

#define XKB_KEY_Meta_L                        0xffe7  /* Left meta */
#define XKB_KEY_Meta_R                        0xffe8  /* Right meta */
#define XKB_KEY_Alt_L                         0xffe9  /* Left alt */
#define XKB_KEY_Alt_R                         0xffea  /* Right alt */
#define XKB_KEY_Super_L                       0xffeb  /* Left super */
#define XKB_KEY_Super_R                       0xffec  /* Right super */
#define XKB_KEY_Hyper_L                       0xffed  /* Left hyper */
#define XKB_KEY_Hyper_R                       0xffee  /* Right hyper */

But how can I get the status of these keys? I did not find an according function for this. Thanks in advance!

x11 keyboard linux c
2 Answers

The correct way to do this is exactly as follows:

Upon receiving KeyPress event, you take the XKeyEvent data, and take the state from it, and convert it as follows (this is a part of GLFW internal mechanism of handling X11 events https://github.com/glfw/glfw/blob/7e8da57094281c73a0be5669a4b79686b4917f6c/src/x11_window.c#L186):

static int translateState(int state)
{
    int mods = 0;

    if (state & ShiftMask)
        mods |= GLFW_MOD_SHIFT;
    if (state & ControlMask)
        mods |= GLFW_MOD_CONTROL;
    if (state & Mod1Mask)
        mods |= GLFW_MOD_ALT;
    if (state & Mod4Mask)
        mods |= GLFW_MOD_SUPER;
    if (state & LockMask)
        mods |= GLFW_MOD_CAPS_LOCK;
    if (state & Mod2Mask)
        mods |= GLFW_MOD_NUM_LOCK;

    return mods;
}

You call that function like:

translateState(xev.xkey.state);

where xev is the XEvent you have received. Of course you should use your own flags instead of GLFW enumeration, or do something else with it.

user_8574270
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