focal (3) XQueryTextExtents.3.gz

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 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