'\"
'\" Copyright (c) 1990 The Regents of the University of California.
'\" Copyright (c) 1994-1998 Sun Microsystems, Inc.
'\"
'\" See the file "license.terms" for information on usage and redistribution
'\" of this file, and for a DISCLAIMER OF ALL WARRANTIES.
'\"
.TH Tk_GetPixelsFromObj 3tk 8.1 Tk "Tk Library Procedures"
.\" The -*- nroff -*- definitions below are for supplemental macros used
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.SH NAME
Tk_GetPixelsFromObj, Tk_GetPixels, Tk_GetMMFromObj, Tk_GetScreenMM \- translate between strings and screen units
.SH SYNOPSIS
.nf
\fB#include <tk.h>\fR
.sp
int
\fBTk_GetPixelsFromObj(\fIinterp, tkwin, objPtr, intPtr\fB)\fR
.sp
int
\fBTk_GetPixels(\fIinterp, tkwin, string, intPtr\fB)\fR
.sp
int
\fBTk_GetMMFromObj(\fIinterp, tkwin, objPtr, doublePtr\fB)\fR
.sp
int
\fBTk_GetScreenMM(\fIinterp, tkwin, string, doublePtr\fB)\fR
.SH ARGUMENTS
.AS "Tcl_Interp" *joinPtr
.AP Tcl_Interp *interp in
Interpreter to use for error reporting.
.AP Tk_Window tkwin in
Window whose screen geometry determines the conversion between absolute
units and pixels.
.AP Tcl_Obj *objPtr in/out
String value specifies a distance on the screen;
internal rep will be modified to cache converted distance.
.AP "const char" *string in
Same as \fIobjPtr\fR except specification of distance is passed as
a string.
.AP int *intPtr out
Pointer to location in which to store converted distance in pixels.
.AP double *doublePtr out
Pointer to location in which to store converted distance in millimeters.
.BE
.SH DESCRIPTION
.PP
These procedures take as argument a specification of distance on
the screen (\fIobjPtr\fR or \fIstring\fR) and compute the
corresponding distance either in integer pixels or floating-point millimeters.
In either case,
\fIobjPtr\fR or \fIstring\fR
specifies a screen distance as a
floating-point number followed by one of the following characters
that indicates units:
.TP
<none>
The number specifies a distance in pixels.
.TP
\fBc\fR
The number specifies a distance in centimeters on the screen.
.TP
\fBi\fR
The number specifies a distance in inches on the screen.
.TP
\fBm\fR
The number specifies a distance in millimeters on the screen.
.TP
\fBp\fR
The number specifies a distance in printer's points (1/72 inch)
on the screen.
.PP
\fBTk_GetPixelsFromObj\fR converts the value of \fIobjPtr\fR to the
nearest even number of pixels and stores that value at \fI*intPtr\fR.
It returns \fBTCL_OK\fR under normal circumstances.
If an error occurs (e.g. \fIobjPtr\fR contains a number followed
by a character that is not one of the ones above) then
\fBTCL_ERROR\fR is returned and an error message is left
in \fIinterp\fR's result if \fIinterp\fR is not NULL.
\fBTk_GetPixelsFromObj\fR caches information about the return
value in \fIobjPtr\fR, which speeds up future calls to
\fBTk_GetPixelsFromObj\fR with the same \fIobjPtr\fR.
.PP
\fBTk_GetPixels\fR is identical to \fBTk_GetPixelsFromObj\fR except
that the screen distance is specified with a string instead
of an object.  This prevents \fBTk_GetPixels\fR from caching the
return value, so \fBTk_GetPixels\fR is less efficient than
\fBTk_GetPixelsFromObj\fR.
.PP
\fBTk_GetMMFromObj\fR and \fBTk_GetScreenMM\fR are similar to
\fBTk_GetPixelsFromObj\fR and \fBTk_GetPixels\fR (respectively) except
that they convert the screen distance to millimeters and
store a double-precision floating-point result at \fI*doublePtr\fR.
.SH KEYWORDS
centimeters, convert, inches, millimeters, pixels, points, screen units