Tk_AllocFontFromObj(3)

NAME
Tk_AllocFontFromObj, Tk_GetFont, Tk_GetFontFromObj, Tk_NameOfFont, Tk_FreeFontFromObj, Tk_FreeFont - maintain database of fonts

SYNOPSIS
#include <tk.h>

Tk_Font
Tk_AllocFontFromObj(interp, tkwin, objPtr)

Tk_Font
Tk_GetFont(interp, tkwin, string)

Tk_Font
Tk_GetFontFromObj(tkwin, objPtr)

const char *
Tk_NameOfFont(tkfont)

Tk_Font
Tk_FreeFontFromObj(tkwin, objPtr)

void
Tk_FreeFont(tkfont)

ARGUMENTS
Interpreter to use for error reporting. If NULL, then no error messages are left after errors. Token for window in which font will be used. Gives name or description of font. See documentation for the font command for details on acceptable formats. Internal rep will be modified to cache corresponding Tk_Font. Same as objPtr except description of font is passed as a string and resulting Tk_Font is not cached. Opaque font token.

DESCRIPTION

Tk_AllocFontFromObj finds the font indicated by objPtr and returns a token that represents the font. The return value can be used in subsequent calls to procedures such as Tk_GetFontMetrics, Tk_MeasureChars, and Tk_FreeFont. The Tk_Font token will remain valid until Tk_FreeFontFromObj or Tk_FreeFont is called to release it. ObjPtr can contain either a symbolic name or a font description; see the documentation for the font command for a description of the valid formats. If Tk_AllocFontFromObj is unsuccessful (because, for example, objPtr did not contain a valid font specification) then it returns NULL and leaves an error message in interp's result if interp is not NULL. Tk_AllocFontFromObj caches information about the return value in objPtr, which speeds up future calls to procedures such as Tk_AllocFontFromObj and Tk_GetFontFromObj.

Tk_GetFont is identical to Tk_AllocFontFromObj except that the description of the font is specified with a string instead of an object. This prevents Tk_GetFont from caching the matching Tk_Font, so Tk_GetFont is less efficient than Tk_AllocFontFromObj.

Tk_GetFontFromObj returns the token for an existing font, given the window and description used to create the font. Tk_GetFontFromObj does not actually create the font; the font must already have been created with a previous call to Tk_AllocFontFromObj or Tk_GetFont. The return value is cached in objPtr, which speeds up future calls to Tk_GetFontFromObj with the same objPtr and tkwin.

Tk_AllocFontFromObj and Tk_GetFont 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.

The procedure Tk_NameOfFont is roughly the inverse of Tk_GetFont. Given a tkfont that was created by Tk_GetFont (or Tk_AllocFontFromObj), the return value is the string argument that was passed to Tk_GetFont to create the font. The string returned by Tk_NameOfFont is only guaranteed to persist until the tkfont is deleted. The caller must not modify this string.

When a font is no longer needed, Tk_FreeFontFromObj or Tk_FreeFont should be called to release it. For Tk_FreeFontFromObj the font to release is specified with the same information used to create it; for Tk_FreeFont the font to release is specified with its Tk_Font token. There should be exactly one call to Tk_FreeFontFromObj or Tk_FreeFont for each call to Tk_AllocFontFromObj or Tk_GetFont.

SEE ALSO
Tk_FontId(3)

KEYWORDS
font