Manpages - XTextExtents.3

NAME

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

SYNTAX

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

int XTextExtents16 ( XFontStruct */font_struct/ , _Xconst 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 , _Xconst 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 , _Xconst 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.