XTextExtents(3)


NAME

   XTextExtents, XTextExtents16, XQueryTextExtents, XQueryTextExtents16 -
   compute or query text extents

SYNTAX

   int XTextExtents(XFontStruct *font_struct, char *string, int nchars,
          int *direction_return, int *font_ascent_return, int
          *font_descent_return, XCharStruct *overall_return);

   int XTextExtents16(XFontStruct *font_struct, XChar2b *string, int
          nchars, int *direction_return, int *font_ascent_return, int
          *font_descent_return, XCharStruct *overall_return);

   int XQueryTextExtents(Display *display, XID font_ID, char *string, int
          nchars, int *direction_return, int *font_ascent_return, int
          *font_descent_return, XCharStruct *overall_return);

   int XQueryTextExtents16(Display *display, XID font_ID, XChar2b *string,
          int nchars, int *direction_return, int *font_ascent_return, int
          *font_descent_return, XCharStruct *overall_return);

ARGUMENTS

   direction_return
             Returns the value of the direction hint (FontLeftToRight or
             FontRightToLeft).

   display   Specifies the connection to the X server.

   font_ID   Specifies either the font ID or the GContext ID that contains
             the font.

   font_ascent_return
             Returns the font ascent.

   font_descent_return
             Returns the font descent.

   font_struct
             Specifies the XFontStruct structure.

   nchars    Specifies the number of characters in the character string.

   string    Specifies the character string.

   overall_return
             Returns the overall size in the specified XCharStruct
             structure.

DESCRIPTION

   The XTextExtents and XTextExtents16 functions perform the size
   computation locally and, thereby, avoid the round-trip overhead of
   XQueryTextExtents and XQueryTextExtents16.  Both functions return an
   XCharStruct structure, whose members are set to the values as follows.

   The ascent member is set to the maximum of the ascent metrics of all
   characters in the string.  The descent member is set to the maximum of
   the descent metrics.  The width member is set to the sum of the
   character-width metrics of all characters in the string.  For each
   character in the string, let W be the sum of the character-width
   metrics of all characters preceding it in the string.  Let L be the
   left-side-bearing metric of the character plus W.  Let R be the right-
   side-bearing metric of the character plus W.  The lbearing member is
   set to the minimum L of all characters in the string.  The rbearing
   member is set to the maximum R.

   For fonts defined with linear indexing rather than 2-byte matrix
   indexing, each XChar2b structure is interpreted as a 16-bit number with
   byte1 as the most significant byte.  If the font has no defined default
   character, undefined characters in the string are taken to have all
   zero metrics.

   The XQueryTextExtents and XQueryTextExtents16 functions return the
   bounding box of the specified 8-bit and 16-bit character string in the
   specified font or the font contained in the specified GC.  These
   functions query the X server and, therefore, suffer the round-trip
   overhead that is avoided by XTextExtents and XTextExtents16.  Both
   functions return a XCharStruct structure, whose members are set to the
   values as follows.

   The ascent member is set to the maximum of the ascent metrics of all
   characters in the string.  The descent member is set to the maximum of
   the descent metrics.  The width member is set to the sum of the
   character-width metrics of all characters in the string.  For each
   character in the string, let W be the sum of the character-width
   metrics of all characters preceding it in the string.  Let L be the
   left-side-bearing metric of the character plus W.  Let R be the right-
   side-bearing metric of the character plus W.  The lbearing member is
   set to the minimum L of all characters in the string.  The rbearing
   member is set to the maximum R.

   For fonts defined with linear indexing rather than 2-byte matrix
   indexing, each XChar2b structure is interpreted as a 16-bit number with
   byte1 as the most significant byte.  If the font has no defined default
   character, undefined characters in the string are taken to have all
   zero metrics.

   Characters with all zero metrics are ignored.  If the font has no
   defined default_char, the undefined characters in the string are also
   ignored.

   XQueryTextExtents and XQueryTextExtents16 can generate BadFont and
   BadGC errors.

DIAGNOSTICS

   BadFont   A value for a Font or GContext argument does not name a
             defined Font.

   BadGC     A value for a GContext argument does not name a defined
             GContext.

SEE ALSO

   XLoadFont(3), XTextWidth(3)
   Xlib - C Language X Interface





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