Tk_MeasureChars(3)
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NAME
Tk_MeasureChars, Tk_TextWidth, Tk_DrawChars, Tk_Under-
lineChars - routines to measure and display simple single-
line strings.
SYNOPSIS
#include <<tk.h>>
int
Tk_MeasureChars(tkfont, string, maxChars, maxPixels, flags, lengthPtr)
int
Tk_TextWidth(tkfont, string, numChars)
void
Tk_DrawChars(display, drawable, gc, tkfont, string, numChars, x, y)
void
Tk_UnderlineChars(display, drawable, gc, tkfont, string, x, y, firstChar, lastChar)
ARGUMENTS
Tk_Font tkfont (in) Token for font in which
text is to be drawn or
measured. Must have
been returned by a pre-
vious call to Tk_Get-
Font.
const char *string (in) Text to be measured or
displayed. Need not be
null terminated. Any
non-printing meta-char-
acters in the string
(such as tabs, new-
lines, and other con-
trol characters) will
be measured or dis-
played in a platform-
dependent manner.
int maxChars (in) The maximum number of
characters to consider
when measuring string.
Must be greater than or
equal to 0.
int maxPixels (in) If maxPixels is greater
than 0, it specifies
the longest permissible
line length in pixels.
Characters from string
are processed only
until this many pixels
have been covered. If
maxPixels is <= 0, then
the line length is
unbounded and the flags
argument is ignored.
int flags (in) Various flag bits OR-ed
together: TK_PARTIAL_OK
means include a charac-
ter as long as any part
of it fits in the
length given by maxPix-
els; otherwise, a char-
acter must fit com-
pletely to be consid-
ered. TK_WHOLE_WORDS
means stop on a word
boundary, if possible.
If TK_AT_LEAST_ONE is
set, it means return at
least one character
even if no characters
could fit in the length
given by maxPixels. If
TK_AT_LEAST_ONE is set
and TK_WHOLE_WORDS is
also set, it means that
if not even one word
fits on the line,
return the first few
letters of the word
that did fit; if not
even one letter of the
word fit, then the
first letter will still
be returned.
int *lengthPtr (out) Filled with the number
of pixels occupied by
the number of charac-
ters returned as the
result of Tk_Mea-
sureChars.
int numChars (in) The total number of
characters to measure
or draw from string.
Must be greater than or
equal to 0.
Display *display (in) Display on which to
draw.
Drawable drawable (in) Window or pixmap in
which to draw.
GC gc (in) Graphics context for
drawing characters.
The font selected into
this GC must be the
same as the tkfont.
int x, y (in) Coordinates at which to
place the left edge of
the baseline when dis-
playing string.
int firstChar (in) The index of the first
character to underline
in the string. Under-
lining begins at the
left edge of this char-
acter.
int lastChar (in) The index of the last
character up to which
the underline will be
drawn. The character
specified by lastChar
will not itself be
underlined.
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DESCRIPTION
These routines are for measuring and displaying simple
single-font, single-line, strings. To measure and display
single-font, multi-line, justified text, refer to the doc-
umentation for Tk_ComputeTextLayout. There is no program-
ming interface in the core of Tk that supports multi-font,
multi-line text; support for that behavior must be built
on top of simpler layers.
A glyph is the displayable picture of a letter, number, or
some other symbol. Not all character codes in a given
font have a glyph. Characters such as tabs, new-
lines/returns, and control characters that have no glyph
are measured and displayed by these procedures in a plat-
form-dependent manner; under X, they are replaced with
backslashed escape sequences, while under Windows and Mac-
intosh hollow or solid boxes may be substituted. Refer to
the documentation for Tk_ComputeTextLayout for a program-
ming interface that supports the platform-independent
expansion of tab characters into columns and new-
lines/returns into multi-line text.
Tk_MeasureChars is used both to compute the length of a
given string and to compute how many characters from a
string fit in a given amount of space. The return value
is the number of characters from string that fit in the
space specified by maxPixels subject to the conditions
described by flags. If all characters fit, the return
value will be maxChars. *lengthPtr is filled with the
computed width, in pixels, of the portion of the string
that was measured. For example, if the return value is 5,
then *lengthPtr is filled with the distance between the
left edge of string[0] and the right edge of string[4].
Tk_TextWidth is a wrapper function that provides a simpler
interface to the Tk_MeasureChars function. The return
value is how much space in pixels the given string needs.
Tk_DrawChars draws the string at the given location in the
given drawable.
Tk_UnderlineChars underlines the given range of characters
in the given string. It doesn't draw the characters
(which are assumed to have been displayed previously by
Tk_DrawChars); it just draws the underline. This proce-
dure is used to underline a few characters without having
to construct an underlined font. To produce natively
underlined text, the appropriate underlined font should be
constructed and used.
KEYWORDS
font