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 GCon
- text.
SEE ALSO
- XLoadFont(3), XTextWidth(3)
Xlib - C Language X Interface