Tk_GetPixelsFromObj(3) Tk Library Procedures Tk_GetPixelsFromObj(3)

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NAME

Tk_GetPixelsFromObj, Tk_GetPixels, Tk_GetMMFromObj, Tk_GetScreenMM -
translate between strings and screen units

SYNOPSIS

#include <tk.h>

int
Tk_GetPixelsFromObj(interp, tkwin, objPtr, intPtr)

int
Tk_GetPixels(interp, tkwin, string, intPtr)

int
Tk_GetMMFromObj(interp, tkwin, objPtr, doublePtr)

int
Tk_GetScreenMM(interp, tkwin, string, doublePtr)

ARGUMENTS

Tcl_Interp *interp (in) Interpreter to use for error
reporting.

Tk_Window tkwin (in) Window whose screen geometry
determines the conversion between
absolute units and pixels.

Tcl_Obj *objPtr (in/out) String value specifies a distance
on the screen; internal rep will be
modified to cache converted
distance.

const char *string (in) Same as objPtr except specification
of distance is passed as a string.

int *intPtr (out) Pointer to location in which to
store converted distance in pixels.

double *doublePtr (out) Pointer to location in which to
store converted distance in
millimeters.
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DESCRIPTION

These procedures take as argument a specification of distance on the
screen (objPtr or string) and compute the corresponding distance
either in integer pixels or floating-point millimeters. In either
case, objPtr or string specifies a screen distance as a floating-
point number followed by one of the following characters that
indicates units:

<none> The number specifies a distance in pixels.

c The number specifies a distance in centimeters on the screen.

i The number specifies a distance in inches on the screen.

m The number specifies a distance in millimeters on the screen.

p The number specifies a distance in printer's points (1/72
inch) on the screen.

Tk_GetPixelsFromObj converts the value of objPtr to the nearest even
number of pixels and stores that value at *intPtr. It returns TCL_OK
under normal circumstances. If an error occurs (e.g. objPtr contains
a number followed by a character that is not one of the ones above)
then TCL_ERROR is returned and an error message is left in interp's
result if interp is not NULL. Tk_GetPixelsFromObj caches information
about the return value in objPtr, which speeds up future calls to
Tk_GetPixelsFromObj with the same objPtr.

Tk_GetPixels is identical to Tk_GetPixelsFromObj except that the
screen distance is specified with a string instead of an object.
This prevents Tk_GetPixels from caching the return value, so
Tk_GetPixels is less efficient than Tk_GetPixelsFromObj.

Tk_GetMMFromObj and Tk_GetScreenMM are similar to Tk_GetPixelsFromObj
and Tk_GetPixels (respectively) except that they convert the screen
distance to millimeters and store a double-precision floating-point
result at *doublePtr.

KEYWORDS

centimeters, convert, inches, millimeters, pixels, points, screen
units

Tk 8.1 Tk_GetPixelsFromObj(3)