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CentOS 7.0 - man page for tk_measurechars (centos section 3)

Tk_MeasureChars(3)		      Tk Library Procedures		       Tk_MeasureChars(3)

_________________________________________________________________________________________________

NAME
       Tk_MeasureChars,  Tk_TextWidth,	Tk_DrawChars, Tk_UnderlineChars - routines to measure and
       display simple single-line strings.

SYNOPSIS
       #include <tk.h>

       int
       Tk_MeasureChars(tkfont, string, numBytes, maxPixels, flags, lengthPtr)

       int
       Tk_TextWidth(tkfont, string, numBytes)

       Tk_DrawChars(display, drawable, gc, tkfont, string, numBytes, x, y)

       Tk_UnderlineChars(display, drawable, gc, tkfont, string, x, y, firstByte, lastByte)

ARGUMENTS
       Tk_Font tkfont (in)		  Token for font in which text is to  be  drawn  or  mea-
					  sured.   Must  have been returned by a previous call to
					  Tk_GetFont.

       const char *string (in)		  Text to be measured or displayed.   Need  not  be  null
					  terminated.	Any  non-printing  meta-characters in the
					  string (such as tabs, newlines, and other control char-
					  acters)  will  be  measured or displayed in a platform-
					  dependent manner.

       int numBytes (in)		  The maximum number of bytes to consider when	measuring
					  or drawing string.  Must be greater than or equal to 0.

       int maxPixels (in)		  If  maxPixels is >= 0, it specifies the longest permis-
					  sible line length in pixels.	 Characters  from  string
					  are  processed  only	until  this many pixels have been
					  covered.  If maxPixels is < 0, then the line length  is
					  unbounded and the flags argument is ignored.

       int flags (in)			  Various  flag  bits OR-ed together: TK_PARTIAL_OK means
					  include a character as long as any part of it  fits  in
					  the  length  given by maxPixels; otherwise, a character
					  must fit completely to be  considered.   TK_WHOLE_WORDS
					  means  stop  on  a  word  boundary,  if  possible.   If
					  TK_AT_LEAST_ONE is set, it means return  at  least  one
					  character even if no characters could fit in the length
					  given by maxPixels.	If  TK_AT_LEAST_ONE  is  set  and
					  TK_WHOLE_WORDS  is  also set, it means that if not even
					  one word fits on the line, return the first few letters
					  of the word that did fit; if not even one letter of the
					  word fit, then the first letter will still be returned.

       int *lengthPtr (out)		  Filled with the number of pixels occupied by the number
					  of   characters  returned  as  the  result  of  Tk_Mea-
					  sureChars.

       Display *display (in)		  Display on which to draw.

       Drawable drawable (in)		  Window or pixmap in which to draw.

       GC gc (in)			  Graphics context  for  drawing  characters.	The  font
					  selected into this GC must be the same as the tkfont.

       int x, y (in)			  Coordinates  at  which  to  place  the left edge of the
					  baseline when displaying string.

       int firstByte (in)		  The index of the first byte of the first  character  to
					  underline  in  the  string.	Underlining begins at the
					  left edge of this character.

       int lastByte (in)		  The index of the first byte of the last character up to
					  which the underline will be drawn.  The character spec-
					  ified by lastByte will not itself be underlined.
_________________________________________________________________

DESCRIPTION
       These routines are for measuring and displaying simple single-font,  single-line  strings.
       To measure and display single-font, multi-line, justified text, refer to the documentation
       for Tk_ComputeTextLayout.  There is no programming interface in the core of Tk  that  sup-
       ports  multi-font, multi-line text; support for that behavior must be built on top of sim-
       pler layers.  Note that the interfaces described here are byte-oriented not character-ori-
       ented,  so index values coming from Tcl scripts need to be converted to byte offsets using
       the Tcl_UtfAtIndex and related routines.

       A glyph is the displayable picture of a letter, number, or some	other  symbol.	 Not  all
       character  codes in a given font have a glyph.  Characters such as tabs, newlines/returns,
       and control characters that have no glyph are measured and displayed by	these  procedures
       in  a  platform-dependent  manner;  under  X,  they  are  replaced with backslashed escape
       sequences, while under Windows and Macintosh hollow or solid  boxes  may  be  substituted.
       Refer  to the documentation for Tk_ComputeTextLayout for a programming interface that sup-
       ports  the  platform-independent  expansion  of	tab  characters  into  columns	and  new-
       lines/returns into multi-line text.

       Tk_MeasureChars	is  used  both to compute the length of a given string and to compute how
       many characters from a string fit in a given amount of space.  The  return  value  is  the
       number  of  bytes  from string that fit in the space specified by maxPixels subject to the
       conditions described by flags.  If all characters fit, the return value will be	numBytes.
       *lengthPtr is filled with the computed width, in pixels, of the portion of the string that
       was measured.  For example, if the return value is 5, then *lengthPtr is filled	with  the
       distance between the left edge of string[0] and the right edge of string[4].

       Tk_TextWidth  is  a  wrapper  function  that  provides  a simpler interface to the Tk_Mea-
       sureChars function.  The return value is how much space in pixels the given string needs.

       Tk_DrawChars draws the string at the given location in the given drawable.

       Tk_UnderlineChars underlines the given range of characters in the given string.	 It  does
       not  draw  the  characters  (which  are	assumed  to  have  been  displayed  previously by
       Tk_DrawChars); it just draws the underline.  This procedure is used  to	underline  a  few
       characters without having to construct an underlined font.  To produce natively underlined
       text, the appropriate underlined font should be constructed and used.

SEE ALSO
       font(n), FontId(3)

KEYWORDS
       font, measurement

Tk					       8.1			       Tk_MeasureChars(3)


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