Switch to Specific Input Source for macOS

set_input_source.cpp

/*
 * Switch to Specific Input Source for macOS
 * Author: SF-Zhou<sfzhou.scut@gmail.com>
 * To English: g++ -framework Foundation -framework Carbon -std=c++11 -O2 change-input-source.cpp -o switch-to-english
 * To Pinyin: g++ -framework Foundation -framework Carbon -std=c++11 -O2 change-input-source.cpp -D PINYIN -o switch-to-pinyin
 */

#include <string>
#include <Carbon/Carbon.h>
#include <ApplicationServices/ApplicationServices.h>

inline void key_stroke(CGKeyCode key, bool press) {
  CGEventSourceRef src = CGEventSourceCreate(kCGEventSourceStateHIDSystemState);
  CGEventRef evt = CGEventCreateKeyboardEvent(src, (CGKeyCode)key, press);
  CGEventPost(kCGHIDEventTap, evt);
  CFRelease(evt);
  CFRelease(src);
}

inline void click(CGKeyCode key) {
  key_stroke(key, true);
  key_stroke(key, false);
}

inline void switch_input_source() {
  click(0x40); // F17, you need set shortcut of switch source to F17
}

inline void switch_to_source(const char *target) {
  TISInputSourceRef source = TISCopyCurrentKeyboardInputSource();
  auto source_name_ref = static_cast<CFStringRef>(
      TISGetInputSourceProperty(source, kTISPropertyInputSourceID));
  auto source_name = std::string(
      CFStringGetCStringPtr(source_name_ref, kCFStringEncodingUTF8));
  if (source_name != target) {
    switch_input_source();
  }
}

int main() {
#ifdef PINYIN
  const char *target = "com.apple.inputmethod.SCIM.ITABC";
#else
  const char *target = "com.apple.keylayout.ABC";
#endif

  switch_to_source(target);
}