Ubuntu Manpage: Tk_MeasureChars, Tk_TextWidth, Tk_DrawChars, Tk_UnderlineChars

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)

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

       void
       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 measured. 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 characters) will be measured or displayed in a
platform-dependent manner. 2

int numBytes (in) 2
The maximum number of bytes to consider when measuring or drawing 2
string. Must be greater than or equal to 0.

int maxPixels (in) If maxPixels is >= 0, it specifies the longest permissible 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_MeasureChars.

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. 2

int firstByte (in) 2
The index of the first byte of the first character to underline in the 2
string. Underlining begins at the left edge of this character. 2

int lastByte (in) 2
The index of the first byte of the last character up to which the 2
underline will be drawn. The character specified by lastByte will not 2
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 supports multi-font, multi-line text; support
       for that behavior must be built on top of simpler layers.  Note that the interfaces  described  here  are 2
       byte-oriented  not  character-oriented,  so  index values coming from Tcl scripts need to be converted to 2
       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
       supports  the  platform-independent  expansion  of  tab characters into columns and newlines/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_MeasureChars 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  doesn't  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.

KEYWORDS

       font

Tk                                                     8.1                                  Tk_MeasureChars(3tk)