gKeyMapper/daemon/uinput_keyboard.h

// gKeyMapper daemon - virtual keyboard for replaying "key" mappings.
#ifndef GKEYMAPPER_DAEMON_UINPUT_KEYBOARD_H
#define GKEYMAPPER_DAEMON_UINPUT_KEYBOARD_H

#include <vector>

#include "mapping.h"

namespace gkeymapper::daemon {

// Key code for a single modifier bit (the "left" variants are enough), 0 when
// the bit is not a modifier.
unsigned short modifier_key_code(unsigned bit);

// Expands one shortcut step into the key codes to press: the modifiers first,
// then the key itself. Used by play() and by the KeyHold action, which has to
// release exactly the codes it pressed.
std::vector<unsigned short> step_key_codes(const gkeymapper::ShortcutStep& step);

// A virtual keyboard created through /dev/uinput. It is only used to replay
// shortcuts; the daemon never reads from it.
class UinputKeyboard {
public:
    UinputKeyboard() = default;
    ~UinputKeyboard();

    UinputKeyboard(const UinputKeyboard&) = delete;
    UinputKeyboard& operator=(const UinputKeyboard&) = delete;

    bool open();
    void close();
    bool is_open() const { return fd_ >= 0; }

    // Presses and releases every step of the shortcut in order.
    void play(const std::vector<gkeymapper::ShortcutStep>& steps);

    // Presses and releases a single Linux key code. The media keys are replayed
    // with this: the keyboard reports them on its own (see README), so the daemon
    // passes them on unchanged instead of turning them into a mapping.
    void tap(unsigned short code);

    // Presses, respectively releases, all codes in one EV_SYN block (release in
    // reverse order). Splitting press and release is what "keyhold" needs: the
    // caller keeps the list and releases it when the G key comes up.
    void press(const std::vector<unsigned short>& codes);
    void release(const std::vector<unsigned short>& codes);

private:
    void emit(unsigned short type, unsigned short code, int value);
    void sync();
    void key_event(unsigned short code, bool down);

    int fd_ = -1;
};

} // namespace gkeymapper::daemon

#endif // GKEYMAPPER_DAEMON_UINPUT_KEYBOARD_H