Tk_MeasureChars (3)

SYNOPSIS

#include <tk.h>
int
Tk_MeasureChars(tkfont, string, maxChars, maxPixels, flags, lengthPtr)
int
Tk_TextWidth(tkfont, string, numChars)
void
Tk_DrawChars(display, drawable, gc, tkfont, string, numChars, x, y)
void
Tk_UnderlineChars(display, drawable, gc, tkfont, string, x, y, firstChar, lastChar)

ARGUMENTS

"const char" firstChar Tk_Font tkfont in Token for font in which text is to be drawn or measured. Must have been returned by a previous call to Tk_GetFont. "const char" *string in Text to be measured or displayed. Need not be null terminated. Any non-printing meta-characters in the string (such as tabs, newlines, and other control characters) will be measured or displayed in a platform-dependent manner. int maxChars in The maximum number of characters to consider when measuring string. Must be greater than or equal to 0. int maxPixels in If maxPixels is greater than 0, it specifies the longest permissible line length in pixels. Characters from string are processed only until this many pixels have been covered. If maxPixels is <= 0, then the line length is unbounded and the flags argument is ignored. int flags in Various flag bits OR-ed together: TK_PARTIAL_OK means include a character as long as any part of it fits in the length given by maxPixels; otherwise, a character must fit completely to be considered. TK_WHOLE_WORDS means stop on a word boundary, if possible. If TK_AT_LEAST_ONE is set, it means return at least one character even if no characters could fit in the length given by maxPixels. If TK_AT_LEAST_ONE is set and TK_WHOLE_WORDS is also set, it means that if not even one word fits on the line, return the first few letters of the word that did fit; if not even one letter of the word fit, then the first letter will still be returned. int *lengthPtr out Filled with the number of pixels occupied by the number of characters returned as the result of Tk_MeasureChars. int numChars in The total number of characters to measure or draw from string. Must be greater than or equal to 0. Display *display in Display on which to draw. Drawable drawable in Window or pixmap in which to draw. GC gc in Graphics context for drawing characters. The font selected into this GC must be the same as the tkfont. int "x, y" in Coordinates at which to place the left edge of the baseline when displaying string. int firstChar in The index of the first character to underline in the string. Underlining begins at the left edge of this character. int lastChar in The index of the last character up to which the underline will be drawn. The character specified by lastChar will not itself be underlined.

DESCRIPTION

These routines are for measuring and displaying simple single-font, single-line, strings. To measure and display single-font, multi-line, justified text, refer to the documentation for Tk_ComputeTextLayout. There is no programming interface in the core of Tk that supports multi-font, multi-line text; support for that behavior must be built on top of simpler layers.

A glyph is the displayable picture of a letter, number, or some other symbol. Not all character codes in a given font have a glyph. Characters such as tabs, newlines/returns, and control characters that have no glyph are measured and displayed by these procedures in a platform-dependent manner; under X, they are replaced with backslashed escape sequences, while under Windows and Macintosh hollow or solid boxes may be substituted. Refer to the documentation for Tk_ComputeTextLayout for a programming interface that supports the platform-independent expansion of tab characters into columns and newlines/returns into multi-line text.

Tk_MeasureChars is used both to compute the length of a given string and to compute how many characters from a string fit in a given amount of space. The return value is the number of characters from string that fit in the space specified by maxPixels subject to the conditions described by flags. If all characters fit, the return value will be maxChars. *lengthPtr is filled with the computed width, in pixels, of the portion of the string that was measured. For example, if the return value is 5, then *lengthPtr is filled with the distance between the left edge of string[0] and the right edge of string[4].

Tk_TextWidth is a wrapper function that provides a simpler interface to the Tk_MeasureChars function. The return value is how much space in pixels the given string needs.

Tk_DrawChars draws the string at the given location in the given drawable.

Tk_UnderlineChars underlines the given range of characters in the given string. It doesn't draw the characters (which are assumed to have been displayed previously by Tk_DrawChars); it just draws the underline. This procedure is used to underline a few characters without having to construct an underlined font. To produce natively underlined text, the appropriate underlined font should be constructed and used.

KEYWORDS

font '\" '\" Copyright (c) 1996 Sun Microsystems, Inc. '\" '\" See the file "license.terms" for information on usage and redistribution '\" of this file, and for a DISCLAIMER OF ALL WARRANTIES. '\" '\" RCS: @(#) $Id: TextLayout.3,v 1.2 1998/09/14 18:22:54 stanton Exp $ '\" '\" The definitions below are for supplemental macros used in Tcl/Tk '\" manual entries. '\" '\" .AP type name in/out ?indent? '\" Start paragraph describing an argument to a library procedure. '\" type is type of argument (int, etc.), in/out is either "in", "out", '\" or "in/out" to describe whether procedure reads or modifies arg, '\" and indent is equivalent to second arg of .IP (shouldn't ever be '\" needed; use .AS below instead) '\" '\" .AS ?type? ?name? '\" Give maximum sizes of arguments for setting tab stops. Type and '\" name are examples of largest possible arguments that will be passed '\" to .AP later. If args are omitted, default tab stops are used. '\" '\" .BS '\" Start box enclosure. From here until next .BE, everything will be '\" enclosed in one large box. '\" '\" .BE '\" End of box enclosure. '\" '\" .CS '\" Begin code excerpt. '\" '\" .CE '\" End code excerpt. '\" '\" .VS ?version? ?br? '\" Begin vertical sidebar, for use in marking newly-changed parts '\" of man pages. The first argument is ignored and used for recording '\" the version when the .VS was added, so that the sidebars can be '\" found and removed when they reach a certain age. If another argument '\" is present, then a line break is forced before starting the sidebar. '\" '\" .VE '\" End of vertical sidebar. '\" '\" .DS '\" Begin an indented unfilled display. '\" '\" .DE '\" End of indented unfilled display. '\" '\" .SO '\" Start of list of standard options for a Tk widget. The '\" options follow on successive lines, in four columns separated '\" by tabs. '\" '\" .SE '\" End of list of standard options for a Tk widget. '\" '\" .OP cmdName dbName dbClass '\" Start of description of a specific option. cmdName gives the '\" option's name as specified in the class command, dbName gives '\" the option's name in the option database, and dbClass gives '\" the option's class in the option database. '\" '\" .UL arg1 arg2 '\" Print arg1 underlined, then print arg2 normally. '\" '\" RCS: @(#) $Id: man.macros,v 1.2 1998/09/14 18:39:54 stanton Exp $ '\" '\" # Set up traps and other miscellaneous stuff for Tcl/Tk man pages. t .wh -1.3i ^B ^l \n(.l b '\" # Start an argument description AP !"\\$4"" .TP \\$4 \{\ !"\\$2"" .TP \\n()Cu .TP 15