XQueryTextExtents16()XQueryTextExtents16()Name
XQueryTextExtents16 – query the server for string and font metrics of a
16-bit character string.
Synopsis
XQueryTextExtents16(display, font_ID, string, nchars, direction_return,
font_ascent_return, descent, overall_return\f(CW)
Display *display;
XID font_ID;
XChar2b *string;
int nchars;
int *direction_return;
int *font_ascent_return, *font_descent_return;
XCharStruct *overall_return\f(CW;
Arguments
display Specifies a connection to an X server; returned from
XOpenDisplay().
font_ID Specifies the appropriate font ID previously returned by
XLoadFont(), or the GContext that specifies the font.
string Specifies the character string for which metrics are to be
returned.
nchars Specifies the number of characters in string.
direction_return
Returns the direction of painting in the specified font.
Either FontLefttoRight or FontRighttoLeft.
font_ascent_return
Returns the maximum ascent in pixels for the specified font.
descent Returns the maximum descent in pixels for the specified font.
overall_return
Returns the overall characteristics of the string. These are
the sum of the width measurements for each character, the
maximum font_ascent_return and descent, the minimum lbearing
added to the width of all characters up to the character with
the smallest lbearing, and the maximum rbearing added to the
width of all characters up to the character with the largest
rbearing.
DescriptionXQueryTextExtents16() returns the dimensions in pixels that specify the
bounding box of the specified string of characters in the named font,
and the maximum ascent and descent for the entire font. This function
queries the server and, therefore, suffers the round trip overhead that
is avoided by XTextExtents16(), but XQueryTextExtents() does not
require a filled XFontInfo structure.
The returned font_ascent_return and font_descent_return should be used
to calculate the line spacing, while the width, rbearing and lbearing
members of overall_return should be used for horizontal measures. The
total height of the bounding rectangle for any string in this font is
font_ascent_return + font_descent_return
overall_return.font_ascent_return is the maximum of the ascent metrics
of all characters in the string. The overall_return.descent is the
maximum of the descent metrics. The overall_return.width is the sum of
the character-width metrics of all characters in the string. The over‐
all_return.lbearing is usually the lbearing of the first character in
the string, and overall_return.rbearing is the rbearing of the last
character in the string plus the sum of the widths of all the charac‐
ters up to but not including the last character. More technically,
here is the X protocol definition: For each character in the string,
let W be the sum of the character-width metrics of all characters pre‐
ceding it in the string, let L be the lbearing metric of the character
plus W, and let R be the rbearing metric of the character plus W. The
overall_return.lbearing is the minimum L of all characters in the
string, and the overall_return.rbearing is the maximum R.
For fonts defined with linear indexing rather than two-byte matrix
indexing, the server interprets each XChar2b as a 16-bit number that
has been transmitted with the most significant byte first. That is,
byte one of the XChar2b is taken as the most significant byte.
If the font has no defined default character, then undefined characters
in the string are taken to have all zero metrics.
Structures
typedef struct { /* normal 16-bit characters are two bytes */
unsigned char byte1;
unsigned char byte2;
} XChar2b;
typedef struct {
short lbearing; /* origin to left edge of character */
short rbearing; /* origin to right edge of character */
short width; /* advance to next char's origin */
short ascent; /* baseline to top edge of character */
short descent; /* baseline to bottom edge of character */
unsigned short attributes; /* per char flags (not predefined) */
} XCharStruct;
Errors
BadFont
BadGC
See AlsoXDrawImageString(), XDrawImageString16(), XDrawString(), XDraw‐
String16(), XDrawText(), XDrawText16(), XQueryTextExtents(), XText‐
Extents(), XTextExtents16(), XTextWidth(), XTextWidth16().
Xlib - Text XQueryTextExtents16()
