Tk_GetPixelsFromObj(3)

💖 Tk_GetPixelsFromObj(3) — Tk Library Procedures 💖

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✨ NAME ✨

The crew: Tk_GetPixelsFromObj, Tk_GetPixels, Tk_GetMMFromObj, Tk_GetScreenMM, Tk_GetDoublePixelsFromObj — translate between strings and screen units. Periodt 💅

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🦋 SYNOPSIS 🦋

#include <tk.h>

int
Tk_GetPixelsFromObj(interp, tkwin, objPtr, intPtr)

int
Tk_GetDoublePixelsFromObj(interp, tkwin, objPtr, doublePtr)

int
Tk_GetPixels(interp, tkwin, string, intPtr)

int
Tk_GetMMFromObj(interp, tkwin, objPtr, doublePtr)

int
Tk_GetScreenMM(interp, tkwin, string, doublePtr)

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🎀 ARGUMENTS 🎀

• Tcl_Interp *interp (in) — the interpreter you use for error reporting, bestie.
• 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 💅

Okay so 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> — no unit character; 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. And yes, Tk_GetPixelsFromObj caches information about the return value in objPtr, which speeds up future calls to Tk_GetPixelsFromObj with the same objPtr ✨

Tk_GetDoublePixelsFromObj is identical to Tk_GetPixelsFromObj except it returns a double not rounded to the nearest integer. No rounding drama 💅

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. Lowkey important, bestie 🫶

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. Millimeter slay 🌸

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🔥 KEYWORDS 🔥

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

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🌈 Sign-off tea: this page is from Tk 8.1 and its title is Tk_GetPixelsFromObj(3); the footer has no date listed, so that's the whole date situation. Bye bestie — go convert those screen units and slay 💅🫶