Add support for Unicode input messages on Windows

src/platform/common.h

@@ -296,6 +296,7 @@ void button_mouse(input_t &input, int button, bool release);
 void scroll(input_t &input, int distance);
 void keyboard(input_t &input, uint16_t modcode, bool release);
 void gamepad(input_t &input, int nr, const gamepad_state_t &gamepad_state);
+void unicode(input_t &input, char *utf8, int size);
 
 int alloc_gamepad(input_t &input, int nr, rumble_queue_t rumble_queue);
 void free_gamepad(input_t &input, int nr);

src/platform/linux/input.cpp

@@ -994,6 +994,10 @@ void keyboard(input_t &input, uint16_t modcode, bool release) {
   keycode.pressed = 1;
 }
 
+void unicode(input_t &input, char *utf8, int size) {
+  BOOST_LOG(info) << "unicode: Unicode input not yet implemented for Linux."sv;
+}
+
 int alloc_gamepad(input_t &input, int nr, rumble_queue_t rumble_queue) {
   return ((input_raw_t *)input.get())->alloc_gamepad(nr, std::move(rumble_queue));
 }

src/platform/macos/input.cpp

@@ -277,6 +277,10 @@ void keyboard(input_t &input, uint16_t modcode, bool release) {
   CGEventPost(kCGHIDEventTap, event);
 }
 
+void unicode(input_t &input, char *utf8, int size) {
+  BOOST_LOG(info) << "unicode: Unicode input not yet implemented for MacOS."sv;
+}
+
 int alloc_gamepad(input_t &input, int nr, rumble_queue_t rumble_queue) {
   BOOST_LOG(info) << "alloc_gamepad: Gamepad not yet implemented for MacOS."sv;
   return -1;

src/platform/windows/input.cpp

@@ -326,6 +326,34 @@ void keyboard(input_t &input, uint16_t modcode, bool release) {
   send_input(i);
 }
 
+void unicode(input_t &input, char *utf8, int size) {
+  // We can do no worse than one UTF-16 character per byte of UTF-8
+  WCHAR wide[size];
+
+  int chars = MultiByteToWideChar(CP_UTF8, MB_ERR_INVALID_CHARS, utf8, size, wide, size);
+  if(chars <= 0) {
+    return;
+  }
+
+  // Send all key down events
+  for(int i = 0; i < chars; i++) {
+    INPUT input {};
+    input.type       = INPUT_KEYBOARD;
+    input.ki.wScan   = wide[i];
+    input.ki.dwFlags = KEYEVENTF_UNICODE;
+    send_input(input);
+  }
+
+  // Send all key up events
+  for(int i = 0; i < chars; i++) {
+    INPUT input {};
+    input.type       = INPUT_KEYBOARD;
+    input.ki.wScan   = wide[i];
+    input.ki.dwFlags = KEYEVENTF_UNICODE | KEYEVENTF_KEYUP;
+    send_input(input);
+  }
+}
+
 int alloc_gamepad(input_t &input, int nr, rumble_queue_t rumble_queue) {
   if(!input) {
     return 0;