Fix broken selection copying

Author: AllyTally

desktop_version/src/TextInput.cpp

@@ -211,7 +211,7 @@ namespace TextInput
             return UTF8_substr(get_line(rect.y), rect.x, rect.x2);
         }
 
-        char* select_part_first_line = UTF8_substr(get_line(rect.y), rect.x, UTF8_total_codepoints(get_line(rect.y)) - rect.x);
+        char* select_part_first_line = UTF8_substr(get_line(rect.y), rect.x, UTF8_total_codepoints(get_line(rect.y)));
         char* select_part_last_line = UTF8_substr(get_line(rect.y2), 0, rect.x2);
 
         // Loop through the lines in between
@@ -221,7 +221,7 @@ namespace TextInput
             total_length += SDL_strlen(get_line(i)) + 1;
         }
 
-        char* select_part = (char*)SDL_malloc(total_length);
+        char* select_part = (char*)SDL_malloc(total_length + 1);
         strcpy(select_part, select_part_first_line);
         strcat(select_part, "\n");
         for (int i = rect.y + 1; i < rect.y2; i++)
@@ -230,6 +230,7 @@ namespace TextInput
             strcat(select_part, "\n");
         }
         strcat(select_part, select_part_last_line);
+        strcat(select_part, "\0");
 
         SDL_free(select_part_first_line);
         SDL_free(select_part_last_line);