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XTextExtents

Section: XLIB FUNCTIONS (3)
Updated: libX11 1.6.3
Index Return to Main Contents
 

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


 

Index

NAME
SYNTAX
ARGUMENTS
DESCRIPTION
DIAGNOSTICS
SEE ALSO


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