Node:CRT, Next:Dos, Up:GPC Units

#### BP compatibility: CRT & WinCRT, portable, with many extensions

The following listing contains the interface of the CRT unit.

`CRT` is a `curses` based unit for text screen handling. It is compatible to BP's `CRT` unit, even in a lot of minor details like the values of function key codes and includes some routines for compatibility with TP5's `Win` unit as well as BP's `WinCRT` and Turbo Power's `TPCrt` units, and some extensions.

The unit has been extended by many functions that were lacking in BP's unit and required assembler code or direct memory/port access to be implemented under BP. The GPC version is now fully suited for portable, real-world programming without any dirty tricks.

The unit is also available as `WinCRT`, completely identical to `CRT`. The only purpose of this "feature" is to let programs written for TPW or BP, with a `uses WinCRT` directive, compile without changes. Unlike TPW/BP's `WinCRT` unit, GPC's unit is not crippled, compared to `CRT`.

To use this unit, you will need the `ncurses` (version 5.0 or newer) or `PDCurses` library which can be found in http://www.gnu-pascal.de/libs/.

    { CRT (Crt Replacement Tool)
      Portable BP compatible CRT unit for GPC with many extensions

      This unit is aware of terminal types. This means programs using
      this unit will work whether run locally or while being logged in
      remotely from a system with a completely different terminal type
      (as long as the appropriate terminfo entry is present on the
      system where the program is run).

      NOTES:

      - The CRT unit needs the ncurses and panel libraries which should
        be available for almost any system. For Dos systems, where
        ncurses is not available, it is configured to use the PDCurses
        and its panel library instead. On Unix systems with X11, it can
        also use PDCurses (xcurses) and xpanel to produce X11 programs.
        The advantage is that the program won't need an xterm with a
        valid terminfo entry, the output may look a little nicer and
        function keys work better than in an xterm, but the disadvantage
        is that it will only run under X. The ncurses and PDCurses
        libraries (including panel and xpanel, resp.) can be found in
        http://www.gnu-pascal.de/libs/
        (Note that ncurses is already installed on many Unix systems.)
        For ncurses, version 5.0 or newer is strongly recommended
        because older versions contain a bug that severely affects CRT
        programs.

        When an X11 version under Unix is wanted, give -DX11 when
        compiling crt.pas and crtc.c (or when compiling crt.pas or a
        program that uses CRT with --automake). On pre-X11R6 systems,
        give -DNOX11R6 additionally. You might also have to give the
        path to the X11 libraries with -L, e.g. -L /usr/X11/lib.

      - A few features cannot be implemented in a portable way and are
        only available on some systems:

          Sound, NoSound 1)                  -----------------------.
          GetShiftState                      ------------------.    |
          TextMode etc. 2)                   -------------.    |    |
          CRTSavePreviousScreen              --------.    |    |    |
          Interrupt signal (Ctrl-C) handling ---.    |    |    |    |
                                                |    |    |    |    |
        Linux/IA32 3) (terminal)                X    X 4) X 5) X 6) X 6)
        Other Unix (terminal)                   X    X 7) X 5) -    -
        Unix (X11 version)                      X    X    - 8) X    -
        Dos (DJGPP)                             X    X    X    X    X
        MS-Windows (Cygwin or mingw)            X    -    X 9) X    -

        Notes:

        1) If you define NO_CRT_DUMMY_SOUND while compiling CRT, you
           will get linking errors when your program tries to use
           Sound/NoSound on a platform where it's not supported (which
           is useful to detect at compile time if playing sound is a
           major task of your program). Otherwise, Sound/NoSound will
           simply do nothing (which is usually acceptable if the program
           uses these routines just for an occasional beep).

        2) Changing to monochrome modes works on all platforms. Changing
           the screen size only works on those indicated. However, even
           on the platforms not supported, the program will react to
           screen size changes by external means (e.g. changing the
           window size with the mouse if running in a GUI window or
           resizing a console or virtual terminal).

        3) Probably also on other processors, but I've had no chance to
           test this yet.

        4) Only on a local console with access permissions to the
           corresponding virtual console memory device or using the
           crtscreen utility (see crtscreen.c in the demos directory).

        5) Only if supported by an external command (e.g., in xterms and
           on local Linux consoles). The command to be called can be
           defined in the environment variable RESIZETERM (where the
           variables columns and lines in the command are set to the
           size wanted). If not set, the code will try resize -s in an
           xterm and otherwise SVGATextMode and setfont. For this to
           work, these utilities need to be present in the PATH or
           /usr/sbin or /usr/local/sbin. Furthermore, SVGATextMode
           and setfont require root permissions, either to the
           executable of the program compiled with CRT or to resizecons
           (called by setfont) or SVGATextMode. To allow the latter, do
           "chmod u+s `which resizecons`" and/or
           "chmod u+s `which SVGATextMode`", as root once, but only if
           you really want each user to be allowed to change the text
           mode.

        6) Only on local consoles.

        7) Some terminals only. Most xterms etc. support it as well as
           other terminals that support an "alternate screen" in the
           smcup/rmcup terminal capabilities.

        8) But the user can resize the window.

        9) Only with PDCurses, not with ncurses. Changing the number of
           screen *columns* doesn't work in a full-screen session.

      - When CRT is initialized (automatically or explicitly; see the
        comments for CRTInit), the screen is cleared, and at the end of
        the program, the cursor is placed at the bottom of the screen
        (curses behaviour).

      - All the other things (including most details like color and
        function key constants) are compatible with BP's CRT unit, and
        there are many extensions that BP's unit does not have.

      - When the screen size is changed by an external event (e.g.,
        resizing an xterm or changing the screen size from another VC
        under Linux), the virtual "function key" kbScreenSizeChanged is
        returned. Applications can use the virtual key to resize their
        windows. kbScreenSizeChanged will not be returned if the screen
        size change was initiated by the program itself (by using
        TextMode or SetScreenSize). Note that TextMode sets the current
        panel to the full screen size, sets the text attribute to the
        default and clears the window (BP compatibility), while
        SetScreenSize does not.

      - After the screen size has been changed, whether by using
        TextMode, SetScreenSize or by an external event, ScreenSize will
        return the new screen size. The current window and all panels
        will have been adjusted to the new screen size. This means, if
        their right or lower ends are outside the new screen size, the
        windows are moved to the left and/or top as far as necessary. If
        this is not enough, i.e., if they are wider/higher than the new
        screen size, they are shrinked to the total screen width/height.
        When the screen size is enlarged, window sizes are not changed,
        with one exception: Windows that extend through the whole screen
        width/height are enlarged to the whole new screen width/height
        (in particular, full-screen windows remain full-screen). This
        behaviour might not be optimal for all purposes, but you can
        always resize your windows in your application after the screen
        size change.

      - (ncurses only) The environment variable ESCDELAY specifies the
        number of milliseconds allowed between an Esc character and
        the rest of an escape sequence (default 1000). Setting it to a
        value too small can cause problems with programs not recognizing
        escape sequences such as function keys, especially over slow
        network connections. Setting it to a value too large can delay
        the recognition of an ESC key press notably. On local Linux
        consoles, e.g., 10 seems to be a good value.

      - When trying to write portable programs, don't rely on exactly
        the same look of your output and the availability of all the key
        combinations. Some kinds of terminals support only some of the
        display attributes and special characters, and usually not all
        of the keys declared are really available. Therefore, it's safer
        to provide the same function on different key combinations and
        to not use the more exotic ones.

      - CRT supports an additional modifier key (if present), called
        Extra. On DJGPP, it's the <Scroll Lock> key, under X11 it's
        the modifier #4, and on a local Linux console, it's the CtrlL
        modifier (value 64) which is unused on many keytabs and can be
        mapped to any key(s), e.g. to those keys on new keyboards with
        these ugly symbols waiting to be replaced by penguins (keycodes
        125 and 127) by inserting the following two lines into your
        /etc/default.keytab and reloading the keytab with loadkeys
        (you usually have to do this as root):

        keycode 125 = CtrlL
        keycode 127 = CtrlL

      Copyright (C) 1998-2003 Free Software Foundation, Inc.

      Author: Frank Heckenbach <frank@pascal.gnu.de>

      This file is part of GNU Pascal.

      GNU Pascal is free software; you can redistribute it and/or modify
      it under the terms of the GNU General Public License as published
      by the Free Software Foundation; either version 2, or (at your
      option) any later version.

      GNU Pascal is distributed in the hope that it will be useful, but
      WITHOUT ANY WARRANTY; without even the implied warranty of
      MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
      General Public License for more details.

      You should have received a copy of the GNU General Public License
      along with GNU Pascal; see the file COPYING. If not, write to the
      Free Software Foundation, 59 Temple Place - Suite 330, Boston, MA
      02111-1307, USA.

      As a special exception, if you link this file with files compiled
      with a GNU compiler to produce an executable, this does not cause
      the resulting executable to be covered by the GNU General Public
      License. This exception does not however invalidate any other
      reasons why the executable file might be covered by the GNU
      General Public License.

      Please also note the license of the curses library used. }

    {$gnu-pascal,I-}
    {$if __GPC_RELEASE__ < 20030303}
    {$error This unit requires GPC release 20030303 or newer.}
    {$endif}

    unit {$ifdef THIS_IS_WINCRT} WinCRT {$else} CRT {$endif};

    interface

    uses GPC;

    const
      { CRT modes }
      BW40          = 0;            { 40x25 Black/White }
      CO40          = 1;            { 40x25 Color }
      BW80          = 2;            { 80x25 Black/White }
      CO80          = 3;            { 80x25 Color }
      Mono          = 7;            { 80x25 Black/White }
      Font8x8       = 256;          { Add-in for 80x43 or 80x50 mode }

      { Mode constants for Turbo Pascal 3.0 compatibility }
      C40           = CO40;
      C80           = CO80;

      { Foreground and background color constants }
      Black         = 0;
      Blue          = 1;
      Green         = 2;
      Cyan          = 3;
      Red           = 4;
      Magenta       = 5;
      Brown         = 6;
      LightGray     = 7;

      { Foreground color constants }
      DarkGray      = 8;
      LightBlue     = 9;
      LightGreen    = 10;
      LightCyan     = 11;
      LightRed      = 12;
      LightMagenta  = 13;
      Yellow        = 14;
      White         = 15;

      { Add-in for blinking }
      Blink         = 128;

    type
      TTextAttr = Byte;

    var
      { If False (default: True), catch interrupt signals (SIGINT;
        Ctrl-C), and other flow control characters as well as SIGTERM,
        SIGHUP and perhaps other signals }
      CheckBreak: Boolean = True; attribute (name = 'crt_CheckBreak');

      { If True (default : False), replace Ctrl-Z by #0 in input }
      CheckEOF: Boolean = False; attribute (name = 'crt_CheckEOF');

      { Ignored -- meaningless here }
      DirectVideo: Boolean = True;

      { Ignored -- curses or the terminal driver will take care of that
        when necessary }
      CheckSnow: Boolean = False;

      { Current (sic!) text mode }
      LastMode: Word = 3; attribute (name = 'crt_LastMode');

      { Current text attribute }
      TextAttr: TTextAttr = 7; attribute (name = 'crt_TextAttr');

      { Window upper left coordinates. *Obsolete*! Please see WindowMin
        below. }
      WindMin: Word = not Word (0); attribute (name = 'crt_WindMin');

      { Window lower right coordinates. *Obsolete*! Please see WindowMax
        below. }
      WindMax: Word = not Word (0); attribute (name = 'crt_WindMax');

    procedure AssignCRT (var f: Text);
    function  KeyPressed: Boolean; external name 'crt_KeyPressed';
    function  ReadKey: Char; external name 'crt_ReadKey';

    { Not effective on all platforms, see above. See also SetScreenSize
      and SetMonochrome. }
    procedure TextMode (Mode: Integer);

    procedure Window (x1, y1, x2, y2: Integer); external
      name 'crt_Window';
    procedure GotoXY (x, y: Integer); external name 'crt_GotoXY';
    function  WhereX: Integer; external name 'crt_WhereX';
    function  WhereY: Integer; external name 'crt_WhereY';
    procedure ClrScr; external name 'crt_ClrScr';
    procedure ClrEOL; external name 'crt_ClrEOL';
    procedure InsLine; external name 'crt_InsLine';
    procedure DelLine; external name 'crt_DelLine';
    procedure TextColor (Color: TTextAttr);
    procedure TextBackground (Color: TTextAttr);
    procedure LowVideo;
    procedure HighVideo;
    procedure NormVideo;
    procedure Delay (MS: Word); external name 'crt_Delay';

    { Not available on all platforms, see above }
    procedure Sound (Hz: Word); external name 'crt_Sound';
    procedure NoSound; external name 'crt_NoSound';

    { =================== Extensions over BP's CRT =================== }

    { Initializes the CRT unit. Should be called before using any of
      CRT's routines.

      Note: For BP compatibility, CRT is initizalized automatically when
      (almost) any of its routines are used for the first time. In this
      case, some defaults are set to match BP more closely. In
      particular, the PC charset (see SetPCCharSet) is enabled then
      (disabled otherwise), and the update level (see SetCRTUpdate) is
      set to UpdateRegularly (UpdateWaitInput otherwise). This feature
      is meant for BP compatibility *only*. Don't rely on it when
      writing a new program. Use CRTInit then, and set the defaults to
      the values you want explicitly.

      SetCRTUpdate is one of those few routines which will not cause CRT
      to be initialized immediately, and a value set with it will
      survive both automatic and explicit initialization, so you can use
      it to set the update level without caring which way CRT will be
      initialized. (This does not apply to SetPCCharSet. Since it works
      on a per-panel basis, it has to initialize CRT first, so there is
      a panel to start with.)

      If you terminate the program before calling CRTInit or any routine
      that causes automatic initialization, curses will never be
      initialized, so e.g., the screen won't be cleared. This can be
      useful, e.g., to check the command line arguments (or anything
      else) and if there's a problem, write an error and abort. Just be
      sure to write the error to StdErr, not Output (because Output will
      be assigned to CRT, and therefore writing to Output will cause CRT
      to be initialized, and because errors belong to StdErr, anyway),
      and to call RestoreTerminal (True) before (just to be sure, in
      case some code -- perhaps added later, or hidden in the
      initialization of some unit -- does initialize CRT). }
    procedure CRTInit; external name 'crt_Init';

    { Changes the input and output file and the terminal description CRT
      uses. Only effective with ncurses, and only if called before CRT
      is initialized (automatically or explicitly; see the comments for
      CRTInit). If TerminalType is nil, the default will be used. If
      InputFile and/or OutputFile are Null, they remain unchanged. }
    procedure CRTSetTerminal (TerminalType: CString; var InputFile,
      OutputFile: AnyFile); attribute (name = 'crt_SetTerminal');

    { If called with an argument True, it causes CRT to save the
      previous screen contents if possible (see the comments at the
      beginning of the unit), and restore them when calling
      RestoreTerminal (True). After RestoreTerminal (False), they're
      saved again, and at the end of the program, they're restored. If
      called with an argument False, it will prohibit this behaviour.
      The default, if this procedure is not called, depends on the
      terminal (generally it is active on most xterms and similar and
      not active on most other terminals).

      This procedure should be called before initializing CRT (using
      CRTInit or automatically), otherwise the previous screen contents
      may already have been overwritten. It has no effect under XCurses,
      because the program uses its own window, anyway. }
    procedure CRTSavePreviousScreen (On: Boolean); external
      name 'crt_SavePreviousScreen';

    { Returns True if CRTSavePreviousScreen was called with argument
      True and the functionality is really available. Note that the
      result is not reliable until CRT is initialized, while
      CRTSavePreviousScreen should be called before CRT is initialized.
      That's why they are two separate routines. }
    function  CRTSavePreviousScreenWorks: Boolean; external
      name 'crt_SavePreviousScreenWorks';

    { If CRT is initialized automatically, not via CRTInit, and
      CRTAutoInitProc is not nil, it will be called before actually
      initializing CRT. }
    var
      CRTAutoInitProc: procedure = nil; attribute (name
      = 'crt_AutoInitProc');

    { Aborts with a runtime error saying that CRT was not initialized.
      If you set CRTAutoInitProc to this procedure, you can effectively
      disable CRT's automatic initialization. }
    procedure CRTNotInitialized; attribute (name
      = 'crt_NotInitialized');

    { Set terminal to shell or curses mode. An internal procedure
      registered by CRT via RegisterRestoreTerminal does this as well,
      so CRTSetCursesMode has to be called only in unusual situations,
      e.g. after executing a process that changes terminal modes, but
      does not restore them (e.g. because it crashed or was killed), and
      the process was not executed with the Execute routine, and
      RestoreTerminal was not called otherwise. If you set it to False
      temporarily, be sure to set it back to True before doing any
      further CRT operations, otherwise the result may be strange. }
    procedure CRTSetCursesMode (On: Boolean); external
      name 'crt_SetCursesMode';

    { Do the same as RestoreTerminal (True), but also clear the screen
      after restoring the terminal (except for XCurses, because the
      program uses its own window, anyway). Does not restore and save
      again the previous screen contents if CRTSavePreviousScreen was
      called. }
    procedure RestoreTerminalClearCRT; attribute (name
      = 'crt_RestoreTerminalClearCRT');

    { Keyboard and character graphics constants -- BP compatible! =:-}
    {$i crt.inc}

    var
      { Tells whether the XCurses version of CRT is used }
      XCRT: Boolean = {$ifdef XCURSES} True {$else} False {$endif};
      attribute (name = 'crt_XCRT');

      { If True (default: False), the Beep procedure and writing #7 do a
        Flash instead }
      VisualBell: Boolean = False; attribute (name = 'crt_VisualBell');

      { Cursor shape codes. Only to be used in very special cases. }
      CursorShapeHidden: Integer = 0; attribute (name
      = 'crt_CursorShapeHidden');
      CursorShapeNormal: Integer = 1; attribute (name
      = 'crt_CursorShapeNormal');
      CursorShapeFull:   Integer = 2; attribute (name
      = 'crt_CursorShapeFull');

    type
      TKey = Word;

      TCursorShape = (CursorIgnored, CursorHidden, CursorNormal,
      CursorFat, CursorBlock);

      TCRTUpdate = (UpdateNever, UpdateWaitInput, UpdateInput,
                    UpdateRegularly, UpdateAlways);

      TPoint = record
        x, y: Integer
      end;

      PCharAttr = ^TCharAttr;
      TCharAttr = record
        ch       : Char;
        Attr     : TTextAttr;
        PCCharSet: Boolean
      end;

      PCharAttrs = ^TCharAttrs;
      TCharAttrs = array [1 .. MaxVarSize div SizeOf (TCharAttr)] of
      TCharAttr;

      TWindowXYInternalCard8 = Cardinal attribute (Size = 8);
      TWindowXYInternalFill = Integer attribute (Size = BitSizeOf (Word)
      - 16);
      TWindowXY = packed record
        {$ifdef __BYTES_BIG_ENDIAN__}
        Fill: TWindowXYInternalFill;
        y, x: TWindowXYInternalCard8
        {$elif defined (__BYTES_LITTLE_ENDIAN__)}
        x, y: TWindowXYInternalCard8;
        Fill: TWindowXYInternalFill
        {$else}
        {$error Endianness is not defined!}
        {$endif}
      end;

    { Make sure TWindowXY really has the same size as WindMin and
      WindMax. If not, compilation will abort here with `division by
      zero'. Otherwise, the value of the constant will always be 1, and
      is of no further interest. }
    const
      AssertTWindowXYSize = 1 / Ord ((SizeOf (TWindowXY) = SizeOf
      (WindMin)) and
                                     (SizeOf (TWindowXY) = SizeOf
      (WindMax)));

    var
      { Window upper and left coordinates. More comfortable to access
        than WindMin, but also *obsolete*. WindMin and WindowMin still
        work, but have the problem that they implicitly limit the window
        size to 255x255 characters. Though that's not really small for a
        text window, it's easily possible to create bigger ones (e.g. in
        an xterm with a small font, on a high resolution screen and/or
        extending over several virutal desktops). When using coordinates
        greater than 254, the corresponding bytes in WindowMin/WindowMax
        will be set to 254, so, e.g., programs which do
        Inc (WindowMin.x) will not fail quite as badly (but probably
        still fail). The routines Window and GetWindow use Integer
        coordinates, and don't suffer from any of these problems, so
        they should be used instead. }
      WindowMin: TWindowXY absolute WindMin;

      { Window lower right coordinates. More comfortable to access than
        WindMax, but also *obsolete* (see the comments for WindowMin).
        Use Window and GetWindow instead. }
      WindowMax: TWindowXY absolute WindMax;

      { The attribute set by NormVideo }
      NormAttr: TTextAttr = 7; attribute (name = 'crt_NormAttr');

      { Tells whether the current mode is monochrome }
      IsMonochrome: Boolean = False; attribute (name
      = 'crt_IsMonochrome');

      { This value can be set to a combination of the shFoo constants
        and will be ORed to the actual shift state returned by
        GetShiftState. This can be used to easily simulate shift keys on
        systems where they can't be accessed. }
      VirtualShiftState: Integer = 0; attribute (name
      = 'crt_VirtualShiftState');

    { Returns the size of the screen. Note: In BP's WinCRT unit,
      ScreenSize is a variable. But since writing to it from a program
      is pointless, anyway, providing a function here should not cause
      any incompatibility. }
    function  ScreenSize: TPoint; attribute (name
      = 'crt_GetScreenSize');

    { Change the screen size if possible. }
    procedure SetScreenSize (x, y: Integer); external
      name 'crt_SetScreenSize';

    { Turns colors off or on. }
    procedure SetMonochrome (Monochrome: Boolean); external
      name 'crt_SetMonochrome';

    { Tell which modifier keys are currently pressed. The result is a
      combination of the shFoo constants defined in crt.inc, or 0 on
      systems where this function is not supported -- but note
      VirtualShiftState. If supported, ReadKey automatically converts
      kbIns and kbDel keys to kbShIns and kbShDel, resp., if shift is
      pressed. }
    function  GetShiftState: Integer; external name 'crt_GetShiftState';

    { Get the extent of the current window. Use this procedure rather
      than reading WindMin and WindMax or WindowMin and WindowMax, since
      this routine allows for window sizes larger than 255. The
      resulting coordinates are 1-based (like in Window, unlike WindMin,
      WindMax, WindowMin and WindowMax). Any of the parameters may be
      Null in case you're interested in only some of the coordinates. }
    procedure GetWindow (var x1, y1, x2, y2: Integer); external
      name 'crt_GetWindow';

    { Determine when to update the screen. The possible values are the
      following. The given conditions *guarantee* updates. However,
      updates may occur more frequently (even if the update level is set
      to UpdateNever). About the default value, see the comments for
      CRTInit.

      UpdateNever    : never (unless explicitly requested with
                       CRTUpdate)
      UpdateWaitInput: before Delay and CRT input, unless typeahead is
                       detected
      UpdateInput    : before Delay and CRT input
      UpdateRegularly: before Delay and CRT input and otherwise in
                       regular intervals without causing too much
                       refresh. This uses a timer on some systems
                       (currently, Unix with ncurses). This was created
                       for BP compatibility, but for many applications,
                       a lower value causes less flickering in the
                       output, and additionally, timer signals won't
                       disturb other operations. Under DJGPP, this
                       always updates immediately, but this fact should
                       not mislead DJGPP users into thinking this is
                       always so.
      UpdateAlways   : after each output. This can be very slow. (Not so
                       under DJGPP, but this fact should not mislead
                       DJGPP users ...) }
    procedure SetCRTUpdate (UpdateLevel: TCRTUpdate); external
      name 'crt_SetUpdateLevel';

    { Do an update now, independently of the update level }
    procedure CRTUpdate; external name 'crt_Update';

    { Do an update now and completely redraw the screen }
    procedure CRTRedraw; external name 'crt_Redraw';

    { Return Ord (key) for normal keys and $100 * Ord (fkey) for
      function keys }
    function  ReadKeyWord: TKey; external name 'crt_ReadKeyWord';

    { Extract the character and scan code from a TKey value }
    function  Key2Char (k: TKey): Char;
    function  Key2Scan (k: TKey): Char;

    { Convert a key to upper/lower case if it is a letter, leave it
      unchanged otherwise }
    function  UpCaseKey (k: TKey): TKey;
    function  LoCaseKey (k: TKey): TKey;

    { Return key codes for the combination of the given key with Ctrl,
      Alt, AltGr or Extra, resp. Returns 0 if the combination is
      unknown. }
    function  CtrlKey  (ch: Char): TKey; attribute (name
      = 'crt_CtrlKey');
    function  AltKey   (ch: Char): TKey; external name 'crt_AltKey';
    function  AltGrKey (ch: Char): TKey; external name 'crt_AltGrKey';
    function  ExtraKey (ch: Char): TKey; external name 'crt_ExtraKey';

    { Check if k is a pseudo key generated by a deadly signal trapped }
    function  IsDeadlySignal (k: TKey): Boolean;

    { Produce a beep or a screen flash }
    procedure Beep; external name 'crt_Beep';
    procedure Flash; external name 'crt_Flash';

    { Get size of current window (calculated using GetWindow) }
    function  GetXMax: Integer;
    function  GetYMax: Integer;

    { Get/goto an absolute position }
    function  WhereXAbs: Integer;
    function  WhereYAbs: Integer;
    procedure GotoXYAbs (x, y: Integer);

    { Turn scrolling on or off }
    procedure SetScroll (State: Boolean); external name 'crt_SetScroll';

    { Read back whether scrolling is enabled }
    function  GetScroll: Boolean; external name 'crt_GetScroll';

    { Determine whether to interpret non-ASCII characters as PC ROM
      characters (True), or in a system dependent way (False). About the
      default, see the comments for CRTInit. }
    procedure SetPCCharSet (PCCharSet: Boolean); external
      name 'crt_SetPCCharSet';

    { Read back the value set by SetPCCharSet }
    function  GetPCCharSet: Boolean; external name 'crt_GetPCCharSet';

    { Determine whether to interpret #7, #8, #10, #13 as control
      characters (True, default), or as graphics characters (False) }
    procedure SetControlChars (UseControlChars: Boolean); external
      name 'crt_SetControlChars';

    { Read back the value set by SetControlChars }
    function  GetControlChars: Boolean; external
      name 'crt_GetControlChars';

    procedure SetCursorShape (Shape: TCursorShape); external
      name 'crt_SetCursorShape';
    function  GetCursorShape: TCursorShape; external
      name 'crt_GetCursorShape';

    procedure HideCursor;
    procedure HiddenCursor;
    procedure NormalCursor;
    procedure FatCursor;
    procedure BlockCursor;
    procedure IgnoreCursor;

    { Simulates a block cursor by writing a block character onto the
      cursor position. The procedure automatically finds the topmost
      visible panel whose shape is not CursorIgnored and places the
      simulated cursor there (just like the hardware cursor), with
      matching attributes, if the cursor shape is CursorFat or
      CursorBlock (otherwise, no simulated cursor is shown).

      Calling this procedure again makes the simulated cursor disappear.
      In particular, to get the effect of a blinking cursor, you have to
      call the procedure repeatedly (say, 8 times a second). CRT will
      not do this for you, since it does not intend to be your main
      event loop. }
    procedure SimulateBlockCursor; external
      name 'crt_SimulateBlockCursor';

    { Makes the cursor simulated by SimulateBlockCursor disappear if it
      is active. Does nothing otherwise. You should call this procedure
      after using SimulateBlockCursor before doing any further CRT
      output (though failing to do so should not hurt except for
      possibly leaving the simulated cursor in its old position longer
      than it should). }
    procedure SimulateBlockCursorOff; external
      name 'crt_SimulateBlockCursorOff';

    function  GetTextColor: Integer;
    function  GetTextBackground: Integer;

    { Write string at the given position without moving the cursor.
      Truncated at the right margin. }
    procedure WriteStrAt (x, y: Integer; const s: String; Attr:
      TTextAttr);

    { Write (several copies of) a char at then given position without
      moving the cursor. Truncated at the right margin. }
    procedure WriteCharAt (x, y, Count: Integer; ch: Char; Attr:
      TTextAttr);

    { Write characters with specified attributes at the given position
      without moving the cursor. Truncated at the right margin. }
    procedure WriteCharAttrAt (x, y, Count: Integer; CharAttr:
      PCharAttrs); external name 'crt_WriteCharAttrAt';

    { Write a char while moving the cursor }
    procedure WriteChar (ch: Char);

    { Read a character from a screen position }
    procedure ReadChar (x, y: Integer; var ch: Char; var Attr:
      TTextAttr); external name 'crt_ReadChar';

    { Change only text attributes, leave characters. Truncated at the
      right margin. }
    procedure ChangeTextAttr (x, y, Count: Integer; NewAttr: TTextAttr);

    { Fill current window }
    procedure FillWin (ch: Char; Attr: TTextAttr); external
      name 'crt_FillWin';

    { Calculate size of memory required for ReadWin in current window. }
    function  WinSize: SizeType; external name 'crt_WinSize';

    { Save window contents. Buf must be WinSize bytes large. }
    procedure ReadWin (var Buf); external name 'crt_ReadWin';

    { Restore window contents saved by ReadWin. The size of the current
      window must match the size of the window from which ReadWin was
      used, but the position may be different. }
    procedure WriteWin (const Buf); external name 'crt_WriteWin';

    type
      WinState = record
        x1, y1, x2, y2, WhereX, WhereY, NewX1, NewY1, NewX2, NewY2:
      Integer;
        TextAttr: TTextAttr;
        CursorShape: TCursorShape;
        ScreenSize: TPoint;
        Buffer: ^Byte
      end;

    { Save window position and size, cursor position, text attribute and
      cursor shape -- *not* the window contents. }
    procedure SaveWin (var State: WinState);

    { Make a new window (like Window), and save the contents of the
      screen below the window as well as the position and size, cursor
      position, text attribute and cursor shape of the old window. }
    procedure MakeWin (var State: WinState; x1, y1, x2, y2: Integer);

    { Create window in full size, save previous text mode and all values
      that MakeWin does. }
    procedure SaveScreen (var State: WinState);

    { Restore the data saved by SaveWin, MakeWin or SaveScreen. }
    procedure RestoreWin (var State: WinState);

    { Panels }

    type
      TPanel = Pointer;

    function  GetActivePanel: TPanel; external
      name 'crt_GetActivePanel';
    procedure PanelNew                 (x1, y1, x2, y2: Integer;
      BindToBackground: Boolean); external name 'crt_PanelNew';
    procedure PanelDelete              (Panel: TPanel); external
      name 'crt_PanelDelete';
    procedure PanelBindToBackground    (Panel: TPanel; BindToBackground:
      Boolean); external name 'crt_PanelBindToBackground';
    function  PanelIsBoundToBackground (Panel: TPanel): Boolean;
      external name 'crt_PanelIsBoundToBackground';
    procedure PanelActivate            (Panel: TPanel); external
      name 'crt_PanelActivate';
    procedure PanelHide                (Panel: TPanel); external
      name 'crt_PanelHide';
    procedure PanelShow                (Panel: TPanel); external
      name 'crt_PanelShow';
    function  PanelHidden              (Panel: TPanel): Boolean;
      external name 'crt_PanelHidden';
    procedure PanelTop                 (Panel: TPanel); external
      name 'crt_PanelTop';
    procedure PanelBottom              (Panel: TPanel); external
      name 'crt_PanelBottom';
    procedure PanelMoveAbove           (Panel, Above: TPanel); external
      name 'crt_PanelMoveAbove';
    procedure PanelMoveBelow           (Panel, Below: TPanel); external
      name 'crt_PanelMoveBelow';
    function  PanelAbove               (Panel: TPanel): TPanel; external
      name 'crt_PanelAbove';
    function  PanelBelow               (Panel: TPanel): TPanel; external
      name 'crt_PanelBelow';

    { TPCRT compatibility }

    { Write a string at the given position without moving the cursor.
      Truncated at the right margin. }
    procedure WriteString (const s: String; y, x: Integer);

    { Write a string at the given position with the given attribute
      without moving the cursor. Truncated at the right margin. }
    procedure FastWriteWindow (const s: String; y, x: Integer; Attr:
      TTextAttr);

    { Write a string at the given absolute position with the given
     attribute without moving the cursor. Truncated at the right
      margin. }
    procedure FastWrite       (const s: String; y, x: Integer; Attr:
      TTextAttr);

    { WinCRT compatibility }

    const
      cw_UseDefault = Integer ($8000);

    var
      WindowOrg : TPoint = (cw_UseDefault, cw_UseDefault);  { Ignored }
      WindowSize: TPoint = (cw_UseDefault, cw_UseDefault);  { Ignored }
      Cursor    : TPoint = (0, 0); attribute (name = 'crt_Cursor');
      { Cursor location, 0-based }
      Origin    : TPoint = (0, 0);  { Ignored }
      InactiveTitle: PChar = '(Inactive %s)';  { Ignored }
      AutoTracking: Boolean = True;  { Ignored }
      WindowTitle: {$ifdef __BP_TYPE_SIZES__}
                   array [0 .. 79] of Char
                   {$else}
                   TStringBuf
                   {$endif};  { CRT window title, ignored }

    procedure InitWinCRT; attribute (name = 'crt_InitWinCRT');

    { Halts the program }
    procedure DoneWinCRT; attribute (noreturn, name = 'crt_DoneWinCRT');

    procedure WriteBuf (Buffer: PChar; Count: SizeType); attribute (name
      = 'crt_WriteBuf');

    function  ReadBuf (Buffer: PChar; Count: SizeType): SizeType;
      attribute (name = 'crt_ReadBuf');

    { 0-based coordinates! }
    procedure CursorTo (x, y: Integer); attribute (name
      = 'crt_CursorTo');

    { Dummy }
    procedure ScrollTo (x, y: Integer); attribute (name
      = 'crt_ScrollTo');

    { Dummy }
    procedure TrackCursor; attribute (name = 'crt_TrackCursor');