GetFont.3

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'\" Copyright (c) 1990-1992 The Regents of the University of California.
'\" Copyright (c) 1994-1998 Sun Microsystems, Inc.
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.so man.macros
.TH Tk_AllocFontFromObj 3 8.1 Tk "Tk Library Procedures"
.BS
.SH NAME
Tk_AllocFontFromObj, Tk_GetFont, Tk_GetFontFromObj, Tk_NameOfFont, Tk_FreeFontFromObj, Tk_FreeFont \- maintain database of fonts
.SH SYNOPSIS
.nf
\fB#include <tk.h>\fR
.sp
Tk_Font 
\fBTk_AllocFontFromObj(\fIinterp, tkwin, objPtr\fB)\fR
.sp
Tk_Font 
\fBTk_GetFont(\fIinterp, tkwin, string\fB)\fR 
.sp
Tk_Font 
\fBTk_GetFontFromObj(\fItkwin, objPtr\fB)\fR
.sp
const char *
\fBTk_NameOfFont(\fItkfont\fB)\fR
.sp
Tk_Font 
\fBTk_FreeFontFromObj(\fItkwin, objPtr\fB)\fR
.sp
void
\fBTk_FreeFont(\fItkfont\fB)\fR

.SH ARGUMENTS
.AS "const char" *tkfont
.AP "Tcl_Interp" *interp in
Interpreter to use for error reporting.  If \fBNULL\fR, then no error
messages are left after errors.
.AP Tk_Window tkwin in
Token for window in which font will be used.
.AP Tcl_Obj *objPtr in/out
Gives name or description of font.  See documentation
for the \fBfont\fR command for details on acceptable formats.
Internal rep will be modified to cache corresponding Tk_Font.
.AP "const char" *string in
Same as \fIobjPtr\fR except description of font is passed as a string and
resulting Tk_Font is not cached.
.AP Tk_Font tkfont in
Opaque font token.
.BE
.SH DESCRIPTION
.PP
\fBTk_AllocFontFromObj\fR finds the font indicated by \fIobjPtr\fR and
returns a token that represents the font.  The return value can be used
in subsequent calls to procedures such as \fBTk_GetFontMetrics\fR,
\fBTk_MeasureChars\fR, and \fBTk_FreeFont\fR.  The Tk_Font token
will remain valid until
\fBTk_FreeFontFromObj\fR or \fBTk_FreeFont\fR is called to release it. 
\fIObjPtr\fR can contain either a symbolic name or a font description; see
the documentation for the \fBfont\fR command for a description of the
valid formats.  If \fBTk_AllocFontFromObj\fR is unsuccessful (because,
for example, \fIobjPtr\fR did not contain a valid font specification) then it
returns \fBNULL\fR and leaves an error message in \fIinterp\fR's result
if \fIinterp\fR is not \fBNULL\fR.  \fBTk_AllocFontFromObj\fR caches
information about the return
value in \fIobjPtr\fR, which speeds up future calls to procedures
such as \fBTk_AllocFontFromObj\fR and \fBTk_GetFontFromObj\fR.
.PP
\fBTk_GetFont\fR is identical to \fBTk_AllocFontFromObj\fR except
that the description of the font is specified with a string instead
of an object.  This prevents \fBTk_GetFont\fR from caching the
matching Tk_Font, so \fBTk_GetFont\fR is less efficient than
\fBTk_AllocFontFromObj\fR.
.PP
\fBTk_GetFontFromObj\fR returns the token for an existing font, given
the window and description used to create the font.
\fBTk_GetFontFromObj\fR does not actually create the font; the font
must already have been created with a previous call to
\fBTk_AllocFontFromObj\fR or \fBTk_GetFont\fR.  The return
value is cached in \fIobjPtr\fR, which speeds up
future calls to \fBTk_GetFontFromObj\fR with the same \fIobjPtr\fR
and \fItkwin\fR.
.PP
\fBTk_AllocFontFromObj\fR and \fBTk_GetFont\fR maintain
a database of all fonts they have allocated.  If
the same font is requested multiple times (e.g. by different
windows or for different purposes), then a single Tk_Font will be
shared for all uses.  The underlying resources will be freed automatically
when no-one is using the font anymore.
.PP
The procedure \fBTk_NameOfFont\fR is roughly the inverse of
\fBTk_GetFont\fR.  Given a \fItkfont\fR that was created by
\fBTk_GetFont\fR (or \fBTk_AllocFontFromObj\fR), the return value is
the \fIstring\fR argument that was
passed to \fBTk_GetFont\fR to create the font.  The string returned by
\fBTk_NameOfFont\fR is only guaranteed to persist until the \fItkfont\fR
is deleted.  The caller must not modify this string.
.PP
When a font is no longer needed,
\fBTk_FreeFontFromObj\fR or \fBTk_FreeFont\fR should be called to
release it.  For \fBTk_FreeFontFromObj\fR the font to release is specified
with the same information used to create it; for
\fBTk_FreeFont\fR the font to release is specified
with its Tk_Font token.  There should be
exactly one call to \fBTk_FreeFontFromObj\fR or \fBTk_FreeFont\fR
for each call to \fBTk_AllocFontFromObj\fR or \fBTk_GetFont\fR.

.SH "SEE ALSO"
Tk_FontId(3)
.SH KEYWORDS
font