emacs/mac/inc/macterm.h

/* Display module for Mac OS.
   Copyright (C) 2000 Free Software Foundation, Inc.

This file is part of GNU Emacs.

GNU Emacs 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 Emacs 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 Emacs; see the file COPYING.  If not, write to
the Free Software Foundation, Inc., 59 Temple Place - Suite 330,
Boston, MA 02111-1307, USA.  */

/* Contributed by Andrew Choi (akochoi@users.sourceforge.net).  */

#include "macgui.h"
#include "frame.h"

/* The class of this X application.  */
#define EMACS_CLASS "Emacs"

#define RGB_TO_ULONG(r, g, b) (((r) << 16) | ((g) << 8) | (b))

#define RED_FROM_ULONG(color) ((color) >> 16)
#define GREEN_FROM_ULONG(color) (((color) >> 8) & 0xff)
#define BLUE_FROM_ULONG(color) ((color) & 0xff)

#define BLACK_PIX_DEFAULT(f) RGB_TO_ULONG(0,0,0)
#define WHITE_PIX_DEFAULT(f) RGB_TO_ULONG(255,255,255)

#define FONT_WIDTH(f)   ((f)->max_bounds.width)
#define FONT_HEIGHT(f)  ((f)->ascent + (f)->descent)
#define FONT_BASE(f)    ((f)->ascent)
#define FONT_DESCENT(f) ((f)->descent)

#define FONT_MAX_WIDTH(f) FONT_WIDTH(f)  /* fix later */

enum text_cursor_kinds {
  NO_CURSOR = -1,
  FILLED_BOX_CURSOR,
  HOLLOW_BOX_CURSOR,
  BAR_CURSOR
};

/* Structure recording bitmaps and reference count.
   If REFCOUNT is 0 then this record is free to be reused.  */

struct mac_bitmap_record 
{
  char *bitmap_data;
  int refcount;
  int height, width;
};


/* For each display (currently only one on mac), we have a structure that
   records information about it.  */

struct mac_display_info
{
  /* Chain of all mac_display_info structures.  */
  struct mac_display_info *next;

  /* This is a cons cell of the form (NAME . FONT-LIST-CACHE).
     The same cons cell also appears in x_display_name_list.  */
  Lisp_Object name_list_element;

  /* Number of frames that are on this display.  */
  int reference_count;

  /* Dots per inch of the screen.  */
  double resx, resy;

  /* Number of planes on this screen.  */
  int n_planes;

  /* Number of bits per pixel on this screen.  */
  int n_cbits;

  /* Dimensions of this screen.  */
  int height, width;
#if 0
  int height_in,width_in;
#endif

  /* Mask of things that cause the mouse to be grabbed.  */
  int grabbed;

#if 0
  /* Emacs bitmap-id of the default icon bitmap for this frame.
     Or -1 if none has been allocated yet.  */
  int icon_bitmap_id;

#endif
  /* The root window of this screen.  */
  Window root_window;

  /* The cursor to use for vertical scroll bars.  */
  Cursor vertical_scroll_bar_cursor;

#if 0
  /* color palette information.  */
  int has_palette;
  struct w32_palette_entry * color_list;
  unsigned num_colors;
  HPALETTE palette;

  /* deferred action flags checked when starting frame update.  */
  int regen_palette;

  /* Keystroke that has been faked by Emacs and will be ignored when
     received; value is reset after key is received.  */
  int faked_key;

#endif

  /* A table of all the fonts we have already loaded.  */
  struct font_info *font_table;

  /* The current capacity of font_table.  */
  int font_table_size;

  /* The number of fonts actually stored in the font table.
     font_table[n] is used and valid iff 0 <= n < n_fonts. 0 <=
     n_fonts <= font_table_size. and font_table[i].name != 0. */
  int n_fonts;

  /* Minimum width over all characters in all fonts in font_table.  */
  int smallest_char_width;

  /* Minimum font height over all fonts in font_table.  */
  int smallest_font_height;

  /* Reusable Graphics Context for drawing a cursor in a non-default face. */
  XGCValues *scratch_cursor_gc;

  /* These variables describe the range of text currently shown in its
     mouse-face, together with the window they apply to. As long as
     the mouse stays within this range, we need not redraw anything on
     its account.  Rows and columns are glyph matrix positions in
     MOUSE_FACE_WINDOW.  */
  int mouse_face_beg_row, mouse_face_beg_col;
  int mouse_face_beg_x, mouse_face_beg_y;
  int mouse_face_end_row, mouse_face_end_col;
  int mouse_face_end_x, mouse_face_end_y;
  int mouse_face_past_end;

  Lisp_Object mouse_face_window;

  int mouse_face_face_id;

  /* 1 if a mouse motion event came and we didn't handle it right away because
     gc was in progress.  */
  int mouse_face_deferred_gc;

  /* FRAME and X, Y position of mouse when last checked for
     highlighting.  X and Y can be negative or out of range for the frame.  */
  struct frame *mouse_face_mouse_frame;

  int mouse_face_mouse_x, mouse_face_mouse_y;

  /* Nonzero means defer mouse-motion highlighting.  */
  int mouse_face_defer;

  int mouse_face_image_state;

  char *mac_id_name;

  /* Pointer to bitmap records.  */
  struct mac_bitmap_record *bitmaps;

  /* Allocated size of bitmaps field.  */
  int bitmaps_size;

  /* Last used bitmap index.  */
  int bitmaps_last;

  /* The frame (if any) which has the window that has keyboard focus.
     Zero if none.  This is examined by Ffocus_frame in w32fns.c.  Note
     that a mere EnterNotify event can set this; if you need to know the
     last frame specified in a FocusIn or FocusOut event, use
     w32_focus_event_frame.  */
  struct frame *x_focus_frame;

  /* The last frame mentioned in a FocusIn or FocusOut event.  This is
     separate from w32_focus_frame, because whether or not LeaveNotify
     events cause us to lose focus depends on whether or not we have
     received a FocusIn event for it.  */
  struct frame *x_focus_event_frame;

  /* The frame which currently has the visual highlight, and should get
     keyboard input (other sorts of input have the frame encoded in the
     event).  It points to the focus frame's selected window's
     frame.  It differs from w32_focus_frame when we're using a global
     minibuffer.  */
  struct frame *x_highlight_frame;

  /* Cache of images.  */
  struct image_cache *image_cache;
};

#define x_display_info mac_display_info

/* This is a chain of structures for all the displays currently in use.  */
extern struct mac_display_info one_mac_display_info;

/* This is a chain of structures for all the X displays currently in use.  */
extern struct x_display_info *x_display_list;

/* This is a list of cons cells, each of the form (NAME . FONT-LIST-CACHE),
   one for each element of x_display_list and in the same order.
   NAME is the name of the frame.
   FONT-LIST-CACHE records previous values returned by x-list-fonts.  */
extern Lisp_Object x_display_name_list;

/* A flag to control how to display unibyte 8-bit character.  */
extern int unibyte_display_via_language_environment;

extern struct x_display_info *x_display_info_for_display P_ ((Display *));
extern struct x_display_info *x_display_info_for_name P_ ((Lisp_Object));

extern struct mac_display_info *mac_term_init ();

/* The collection of data describing a window on the Mac.  Functions
   defined in macterm.c */
struct mac_output {
  WindowPtr mWP;		/* pointer to QuickDraw window */
  FRAME_PTR mFP;		/* points back to the frame struct */

#if 0
  int mNumCols;			/* number of characters per column */
  int mNumRows;			/* number of characters per row */
  int mLineHeight;		/* height of one line of text in pixels */
  int mCharWidth;		/* width of one character in pixels */
  int mHomeX;			/* X pixel coordinate of lower left corner of character at (0, 0) */
  int mHomeY;			/* Y pixel coordinate of lower left corner of character at (0, 0) */
  int mHighlight;		/* current highlight state (0 = off). */
  int mTermWinSize;		/* num of lines from top of window affected by ins_del_lines; set by set_terminal_window. */
#endif

#if 0
  /* stuffs used by xfaces.c */
  struct face **param_faces;
  int n_param_faces;
  struct face **computed_faces;
  int n_computed_faces;
  int size_computed_faces;
#endif

  unsigned long background_pixel;
  unsigned long foreground_pixel;

  /* Position of the Mac window (x and y offsets in global coordinates).  */
  int left_pos;
  int top_pos;

  /* Border width of the W32 window as known by the window system.  */
  int border_width;

  /* Size of the W32 window in pixels.  */
  int pixel_height, pixel_width;

  /* Height of a line, in pixels.  */
  int line_height;

  /* Here are the Graphics Contexts for the default font.  */
  GC normal_gc;				/* Normal video */
  GC reverse_gc;			/* Reverse video */
  GC cursor_gc;				/* cursor drawing */

  /* Width of the internal border.  This is a line of background color
     just inside the window's border.  When the frame is selected,
     a highlighting is displayed inside the internal border.  */
  int internal_border_width;

  /* The window used for this frame.
     May be zero while the frame object is being created
     and the window has not yet been created.  */
  Window window_desc;

  /* The window that is the parent of this window.
     Usually this is a window that was made by the window manager,
     but it can be the root window, and it can be explicitly specified
     (see the explicit_parent field, below).  */
  Window parent_desc;

  /* Default ASCII font of this frame. */
  XFontStruct *font;

  /* The baseline offset of the default ASCII font.  */
  int baseline_offset;

  /* If a fontset is specified for this frame instead of font, this
     value contains an ID of the fontset, else -1.  */
  int fontset;

  /* Pixel values used for various purposes.
     border_pixel may be -1 meaning use a gray tile.  */
  unsigned long cursor_pixel;
  unsigned long border_pixel;
  unsigned long mouse_pixel;
  unsigned long cursor_foreground_pixel;

  /* Foreground color for scroll bars.  A value of -1 means use the
     default (black for non-toolkit scroll bars).  */
  unsigned long scroll_bar_foreground_pixel;
  
  /* Background color for scroll bars.  A value of -1 means use the
     default (background color of the frame for non-toolkit scroll
     bars).  */
  unsigned long scroll_bar_background_pixel;

  /* Descriptor for the cursor in use for this window.  */
  Cursor text_cursor;
  Cursor nontext_cursor;
  Cursor modeline_cursor;
  Cursor cross_cursor;
  Cursor hourglass_cursor;
#if 0
  /* Window whose cursor is hourglass_cursor.  This window is temporarily
     mapped to display a hourglass-cursor.  */
  Window hourglass_window;
  
  /* Non-zero means hourglass cursor is currently displayed.  */
  unsigned hourglass_p : 1;

  /* Flag to set when the window needs to be completely repainted.  */
  int needs_exposure;

#endif

  /* What kind of text cursor is drawn in this window right now?
     (If there is no cursor (phys_cursor_x < 0), then this means nothing.)  */
  enum text_cursor_kinds current_cursor;

  /* What kind of text cursor should we draw in the future?
     This should always be filled_box_cursor or bar_cursor.  */
  enum text_cursor_kinds desired_cursor;

  /* Width of bar cursor (if we are using that).  */
  int cursor_width;

#if 0
  DWORD dwStyle;
#endif

  /* The size of the extra width currently allotted for vertical
     scroll bars, in pixels.  */
  int vertical_scroll_bar_extra;

  /* The extra width currently allotted for the areas in which
     truncation marks, continuation marks, and overlay arrows are
     displayed.  */
  int flags_areas_extra;

  /* This is the gravity value for the specified window position.  */
  int win_gravity;

  /* The geometry flags for this window.  */
  int size_hint_flags;

  /* This is the Emacs structure for the display this frame is on.  */
  /* struct w32_display_info *display_info; */

  /* Nonzero means our parent is another application's window
     and was explicitly specified.  */
  char explicit_parent;

  /* Nonzero means tried already to make this frame visible.  */
  char asked_for_visible;

  /* Nonzero means menubar is currently active.  */
  char menubar_active;

  /* Always contains NULL on the Mac OS because the menu bar is shared.  */
  int menubar_widget;
  
#if 0
  /* Nonzero means menubar is about to become active, but should be
     brought up to date first.  */
  volatile char pending_menu_activation;

#endif
  /* Relief GCs, colors etc.  */
  struct relief
  {
    XGCValues *gc;
    unsigned long pixel;
    int allocated_p;
  }
  black_relief, white_relief;

  /* The background for which the above relief GCs were set up.
     They are changed only when a different background is involved.  */
  unsigned long relief_background;
};

typedef struct mac_output mac_output;

/* Return the Mac window used for displaying data in frame F.  */
#define FRAME_MAC_WINDOW(f) ((f)->output_data.mac->mWP)

#define FRAME_FOREGROUND_PIXEL(f) ((f)->output_data.mac->foreground_pixel)
#define FRAME_BACKGROUND_PIXEL(f) ((f)->output_data.mac->background_pixel)

#define FRAME_FONT(f) ((f)->output_data.mac->font)
#define FRAME_FONTSET(f) ((f)->output_data.mac->fontset)

#define FRAME_INTERNAL_BORDER_WIDTH(f) ((f)->output_data.mac->internal_border_width)
#define FRAME_LINE_HEIGHT(f) ((f)->output_data.mac->line_height)
/* Width of the default font of frame F.  Must be defined by each
   terminal specific header.  */
#define FRAME_DEFAULT_FONT_WIDTH(F) 	FONT_WIDTH (FRAME_FONT (F))
#define FRAME_BASELINE_OFFSET(f) ((f)->output_data.mac->baseline_offset)

/* This gives the w32_display_info structure for the display F is on.  */
#define FRAME_MAC_DISPLAY_INFO(f) (&one_mac_display_info)
#define FRAME_X_DISPLAY_INFO(f) (&one_mac_display_info)

/* This is the `Display *' which frame F is on.  */
#define FRAME_MAC_DISPLAY(f) (0)

/* This is the 'font_info *' which frame F has.  */
#define FRAME_MAC_FONT_TABLE(f) (FRAME_MAC_DISPLAY_INFO (f)->font_table)

/* These two really ought to be called FRAME_PIXEL_{WIDTH,HEIGHT}.  */
#define PIXEL_WIDTH(f) ((f)->output_data.mac->pixel_width)
#define PIXEL_HEIGHT(f) ((f)->output_data.mac->pixel_height)

#define FRAME_DESIRED_CURSOR(f) ((f)->output_data.mac->desired_cursor)

/* Value is the smallest width of any character in any font on frame F.  */

#define FRAME_SMALLEST_CHAR_WIDTH(F) \
     FRAME_MAC_DISPLAY_INFO(F)->smallest_char_width

/* Value is the smallest height of any font on frame F.  */

#define FRAME_SMALLEST_FONT_HEIGHT(F) \
     FRAME_MAC_DISPLAY_INFO(F)->smallest_font_height

/* Return a pointer to the image cache of frame F.  */

#define FRAME_X_IMAGE_CACHE(F) FRAME_MAC_DISPLAY_INFO ((F))->image_cache


/* Pixel width of the bitmaps drawn to indicate truncation,
   continuation etc.  */

#define FRAME_FLAGS_BITMAP_WIDTH(f)	8
#define FRAME_FLAGS_BITMAP_HEIGHT(f)	8

/* Total width of areas reserved for drawing truncation bitmaps,
   continuation bitmaps and alike.  The width is in canonical char
   units of the frame.  This must currently be the case because window
   sizes aren't pixel values.  If it weren't the case, we wouldn't be
   able to split windows horizontally nicely.  */

#define FRAME_X_FLAGS_AREA_COLS(F)				\
     ((2 * FRAME_FLAGS_BITMAP_WIDTH ((F)) + CANON_X_UNIT ((F)) - 1)	\
      / CANON_X_UNIT ((F)))

/* Total width of flags areas in pixels.  */

#define FRAME_X_FLAGS_AREA_WIDTH(F) \
     (FRAME_X_FLAGS_AREA_COLS ((F)) * CANON_X_UNIT ((F)))

/* Pixel-width of the left flags area.  */

#define FRAME_X_LEFT_FLAGS_AREA_WIDTH(F) \
     (FRAME_X_FLAGS_AREA_WIDTH (F) / 2)

/* Pixel-width of the right flags area.  Note that we are doing
   integer arithmetic here, so don't loose a pixel if the total
   width is an odd number.  */

#define FRAME_X_RIGHT_FLAGS_AREA_WIDTH(F) 	\
     (FRAME_X_FLAGS_AREA_WIDTH (F) - FRAME_X_FLAGS_AREA_WIDTH (F) / 2)



/* Mac-specific scroll bar stuff.  */

/* We represent scroll bars as lisp vectors.  This allows us to place
   references to them in windows without worrying about whether we'll
   end up with windows referring to dead scroll bars; the garbage
   collector will free it when its time comes.

   We use struct scroll_bar as a template for accessing fields of the
   vector.  */

struct scroll_bar {

  /* These fields are shared by all vectors.  */
  EMACS_INT size_from_Lisp_Vector_struct;
  struct Lisp_Vector *next_from_Lisp_Vector_struct;

  /* The window we're a scroll bar for.  */
  Lisp_Object window;

  /* The next and previous in the chain of scroll bars in this frame.  */
  Lisp_Object next, prev;

  /* The Mac control handle of this scroll bar.  Since this is a full
     32-bit quantity, we store it split into two 32-bit values.  */
  Lisp_Object control_handle_low, control_handle_high;

  /* The position and size of the scroll bar in pixels, relative to the
     frame.  */
  Lisp_Object top, left, width, height;

  /* The starting and ending positions of the handle, relative to the
     handle area (i.e. zero is the top position, not
     SCROLL_BAR_TOP_BORDER).  If they're equal, that means the handle
     hasn't been drawn yet.

     These are not actually the locations where the beginning and end
     are drawn; in order to keep handles from becoming invisible when
     editing large files, we establish a minimum height by always
     drawing handle bottoms VERTICAL_SCROLL_BAR_MIN_HANDLE pixels below
     where they would be normally; the bottom and top are in a
     different co-ordinate system.  */
  Lisp_Object start, end;

  /* If the scroll bar handle is currently being dragged by the user,
     this is the number of pixels from the top of the handle to the
     place where the user grabbed it.  If the handle isn't currently
     being dragged, this is Qnil.  */
  Lisp_Object dragging;
};

/* The number of elements a vector holding a struct scroll_bar needs.  */
#define SCROLL_BAR_VEC_SIZE					\
  ((sizeof (struct scroll_bar)					\
    - sizeof (EMACS_INT) - sizeof (struct Lisp_Vector *))	\
   / sizeof (Lisp_Object))

/* Turning a lisp vector value into a pointer to a struct scroll_bar.  */
#define XSCROLL_BAR(vec) ((struct scroll_bar *) XVECTOR (vec))


/* Building a 32-bit C integer from two 16-bit lisp integers.  */
#define SCROLL_BAR_PACK(low, high) (XINT (high) << 16 | XINT (low))

/* Setting two lisp integers to the low and high words of a 32-bit C int.  */
#define SCROLL_BAR_UNPACK(low, high, int32) \
  (XSETINT ((low),   (int32)        & 0xffff), \
   XSETINT ((high), ((int32) >> 16) & 0xffff))


/* Extract the Mac control handle of the scroll bar from a struct scroll_bar.  */
#define SCROLL_BAR_CONTROL_HANDLE(ptr) \
  ((ControlHandle) SCROLL_BAR_PACK ((ptr)->control_handle_low, (ptr)->control_handle_high))

/* Store a Mac control handle in a struct scroll_bar.  */
#define SET_SCROLL_BAR_CONTROL_HANDLE(ptr, id) \
  (SCROLL_BAR_UNPACK ((ptr)->control_handle_low, (ptr)->control_handle_high, (int) id))

/* Return the inside width of a vertical scroll bar, given the outside
   width.  */
#define VERTICAL_SCROLL_BAR_INSIDE_WIDTH(f,width) \
  ((width) \
   - VERTICAL_SCROLL_BAR_LEFT_BORDER \
   - VERTICAL_SCROLL_BAR_RIGHT_BORDER \
   - VERTICAL_SCROLL_BAR_WIDTH_TRIM * 2)

/* Return the length of the rectangle within which the top of the
   handle must stay.  This isn't equivalent to the inside height,
   because the scroll bar handle has a minimum height.  

   This is the real range of motion for the scroll bar, so when we're
   scaling buffer positions to scroll bar positions, we use this, not
   VERTICAL_SCROLL_BAR_INSIDE_HEIGHT.  */
#define VERTICAL_SCROLL_BAR_TOP_RANGE(f,height) \
  (VERTICAL_SCROLL_BAR_INSIDE_HEIGHT (f, height) - VERTICAL_SCROLL_BAR_MIN_HANDLE - UP_AND_DOWN_ARROWS)

/* Return the inside height of vertical scroll bar, given the outside
   height.  See VERTICAL_SCROLL_BAR_TOP_RANGE too.  */
#define VERTICAL_SCROLL_BAR_INSIDE_HEIGHT(f,height) \
  ((height) - VERTICAL_SCROLL_BAR_TOP_BORDER - VERTICAL_SCROLL_BAR_BOTTOM_BORDER)


/* Border widths for scroll bars.

   Scroll bar windows don't have any borders; their border width is
   set to zero, and we redraw borders ourselves.  This makes the code
   a bit cleaner, since we don't have to convert between outside width
   (used when relating to the rest of the screen) and inside width
   (used when sizing and drawing the scroll bar window itself).

   The handle moves up and down/back and forth in a rectangle inset
   from the edges of the scroll bar.  These are widths by which we
   inset the handle boundaries from the scroll bar edges.  */
#define VERTICAL_SCROLL_BAR_LEFT_BORDER (0)
#define VERTICAL_SCROLL_BAR_RIGHT_BORDER (0)
#define VERTICAL_SCROLL_BAR_TOP_BORDER (0)
#define VERTICAL_SCROLL_BAR_BOTTOM_BORDER (0)

/* Minimum lengths for scroll bar handles, in pixels.  */
#define VERTICAL_SCROLL_BAR_MIN_HANDLE (16)

/* Combined length of up and down arrow boxes in scroll bars, in pixels.  */
#define UP_AND_DOWN_ARROWS (32)

/* Trimming off a few pixels from each side prevents
   text from glomming up against the scroll bar */
#define VERTICAL_SCROLL_BAR_WIDTH_TRIM (0)


/* Manipulating pixel sizes and character sizes.
   Knowledge of which factors affect the overall size of the window should
   be hidden in these macros, if that's possible.

   Return the upper/left pixel position of the character cell on frame F
   at ROW/COL.  */
#define CHAR_TO_PIXEL_ROW(f, row) \
  ((f)->output_data.mac->internal_border_width \
   + (row) * (f)->output_data.mac->line_height)
#define CHAR_TO_PIXEL_COL(f, col) \
  ((f)->output_data.mac->internal_border_width \
   + (col) * FONT_WIDTH ((f)->output_data.mac->font))

/* Return the pixel width/height of frame F if it has
   WIDTH columns/HEIGHT rows.  */
#define CHAR_TO_PIXEL_WIDTH(f, width) \
  (CHAR_TO_PIXEL_COL (f, width) \
   + (f)->output_data.mac->vertical_scroll_bar_extra \
   + (f)->output_data.mac->flags_areas_extra \
   + (f)->output_data.mac->internal_border_width)
#define CHAR_TO_PIXEL_HEIGHT(f, height) \
  (CHAR_TO_PIXEL_ROW (f, height) \
   + (f)->output_data.mac->internal_border_width)


/* Return the row/column (zero-based) of the character cell containing 
   the pixel on FRAME at ROW/COL.  */
#define PIXEL_TO_CHAR_ROW(f, row) \
  (((row) - (f)->output_data.mac->internal_border_width) \
   / (f)->output_data.mac->line_height)
#define PIXEL_TO_CHAR_COL(f, col) \
  (((col) - (f)->output_data.mac->internal_border_width) \
   / FONT_WIDTH ((f)->output_data.mac->font))

/* How many columns/rows of text can we fit in WIDTH/HEIGHT pixels on
   frame F?  */
#define PIXEL_TO_CHAR_WIDTH(f, width) \
  (PIXEL_TO_CHAR_COL (f, ((width) \
			  - (f)->output_data.mac->internal_border_width \
			  - (f)->output_data.mac->flags_areas_extra \
			  - (f)->output_data.mac->vertical_scroll_bar_extra)))
#define PIXEL_TO_CHAR_HEIGHT(f, height) \
  (PIXEL_TO_CHAR_ROW (f, ((height) \
			  - (f)->output_data.mac->internal_border_width)))

struct frame * check_x_frame (Lisp_Object);

/* Dummy entry for defining tty_display in frame.c.  */
struct x_output
{
  char _dummy;
};