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Tk_AllocFontFromObj(3) Tk Library Procedures Tk_AllocFontFromObj(3)
Tk_AllocFontFromObj, Tk_GetFont, Tk_GetFontFromObj, Tk_NameOfFont,
Tk_FreeFontFromObj, Tk_FreeFont - maintain database of fonts
Tk_AllocFontFromObj(interp, tkwin, objPtr)
Tk_GetFont(interp, tkwin, string)
const char *
Tcl_Interp *interp (in) Interpreter to use for error
reporting. If NULL, then no error
messages are left after errors.
Tk_Window tkwin (in) Token for window in which font will be
Tcl_Obj *objPtr (in/out) Gives name or description of font.
See documentation for the font command
for details on acceptable formats.
Internal rep will be modified to cache
const char *string (in) Same as objPtr except description of
font is passed as a string and
resulting Tk_Font is not cached.
Tk_Font tkfont (in) Opaque font token.
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.
Tk 8.1 Tk_AllocFontFromObj(3)