Tk Library Procedures - Tk_AllocFontFromObj manual page

Tcl/Tk Applications | Tcl Commands | Tk Commands | Tcl Library | Tk Library

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

DESCRIPTION

SEE ALSO

KEYWORDS

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

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 used.

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 corresponding Tk_Font.

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.

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

KEYWORDS

font