Source code in the txr programming language

;;; Type definitions and constants

(typedef BOOL (enum BOOL FALSE TRUE))
(typedef HANDLE cptr)
(typedef WCHAR wchar)
(typedef DWORD uint32)
(typedef WORD uint16)
(typedef SHORT short)

(typedef COORD
         (struct COORD
           (X SHORT)
           (Y SHORT)))

(typedef SMALL_RECT
         (struct SMALL_RECT
           (Left SHORT)
           (Top SHORT)
           (Right SHORT)
           (Bottom SHORT)))

(typedef CONSOLE_SCREEN_BUFFER_INFO
         (struct CONSOLE_SCREEN_BUFFER_INFO
           (dwSize COORD)
           (dwCursorPosition COORD)
           (wAttributes WORD)
           (srWindow SMALL_RECT)
           (dwMaximumWindowSize COORD)))

;;; Various constants

(defvarl STD_INPUT_HANDLE (- #x100000000 10))
(defvarl STD_OUTPUT_HANDLE (- #x100000000 11))
(defvarl STD_ERROR_HANDLE (- #x100000000 12))

(defvarl NULL cptr-null)
(defvarl INVALID_HANDLE_VALUE (cptr-int -1))

;;; Foreign Function Bindings

(with-dyn-lib "kernel32.dll"
  (deffi GetStdHandle "GetStdHandle" HANDLE (DWORD))
  (deffi GetConsoleScreenBufferInfo "GetConsoleScreenBufferInfo"
         BOOL (HANDLE (ptr-out CONSOLE_SCREEN_BUFFER_INFO)))
  (deffi ReadConsoleOutputCharacter "ReadConsoleOutputCharacterW"
         BOOL (HANDLE (ptr-out (array 1 WCHAR))
                       DWORD COORD (ptr-out (array 1 DWORD)))))

;;; Now the character at <2, 5> -- column 3, row 6.

(let ((console-handle (GetStdHandle STD_OUTPUT_HANDLE)))
  (when (equal console-handle INVALID_HANDLE_VALUE)
    (error "couldn't get console handle"))

  (let* ((cinfo (new CONSOLE_SCREEN_BUFFER_INFO))
         (getinfo-ok (GetConsoleScreenBufferInfo console-handle cinfo))
         (coord (if getinfo-ok
                  ^#S(COORD X ,(+ 2 cinfo.srWindow.Left)
                            Y ,(+ 5 cinfo.srWindow.Top))
                  #S(COORD X 0 Y 0)))
         (chars (vector 1))
         (nread (vector 1))
         (read-ok (ReadConsoleOutputCharacter console-handle chars
                                              1 coord nread)))
    (when (eq getinfo-ok 'FALSE)
      (error "GetConsoleScreenBufferInfo failed"))
    (prinl cinfo)
    (when (eq read-ok 'FALSE)
      (error "ReadConsoleOutputCharacter failed"))
    (unless (plusp [nread 0])
      (error "ReadConsoleOutputCharacter read zero characters"))
    (format t "character is ~s\n" [chars 0])))