Manual pages › X Window and screen libraries (3X)

XTextExt(3X)

compute or query text extents

From the original Amiga UNIX 2.1 manual. Some things it mentions may not be in this release.

NAME

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

SYNTAX

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

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

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

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

XWIN 3.0               Last change: 9/1/88                 .ie t

ARGUMENTS

direction_return

Returns the value of the direction hint (FontLeft-ToRight or FontRightToLeft).

display   Specifies the connection to the XWIN 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 a pointer to 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 XChar-Struct 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 charac-
     ters in the string are taken to have all zero metrics.

XWIN 3.0               Last change: 9/1/88                 .ie t

     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 XWIN 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 charac-
     ters in the string are taken to have all zero metrics.

XQueryTextExtents and XQueryTextExtents16 can generate Bad-Font and BadGC errors.

DIAGNOSTICS

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