'\" '\" 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: MeasureChar.3,v 1.7.2.1 2007/11/01 16:37:13 dgp Exp $ '\" .so man.macros .TH Tk_MeasureChars 3 8.1 Tk "Tk Library Procedures" .BS .SH NAME Tk_MeasureChars, Tk_TextWidth, Tk_DrawChars, Tk_UnderlineChars \- routines to measure and display simple single-line strings. .SH SYNOPSIS .nf \fB#include \fR .sp int \fBTk_MeasureChars(\fItkfont, string, numBytes, maxPixels, flags, lengthPtr\fB)\fR .sp int \fBTk_TextWidth(\fItkfont, string, numBytes\fB)\fR .sp void \fBTk_DrawChars(\fIdisplay, drawable, gc, tkfont, string, numBytes, x, y\fB)\fR .sp void \fBTk_UnderlineChars(\fIdisplay, drawable, gc, tkfont, string, x, y, firstByte, lastByte\fB)\fR .sp .SH ARGUMENTS .AS "const char" firstChar .AP 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 \fBTk_GetFont\fR. .AP "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. .AP int numBytes in The maximum number of bytes to consider when measuring or drawing \fIstring\fR. Must be greater than or equal to 0. .AP int maxPixels in If \fImaxPixels\fR is >= 0, it specifies the longest permissible line length in pixels. Characters from \fIstring\fR are processed only until this many pixels have been covered. If \fImaxPixels\fR is < 0, then the line length is unbounded and the \fIflags\fR argument is ignored. .AP int flags in Various flag bits OR-ed together: \fBTK_PARTIAL_OK\fR means include a character as long as any part of it fits in the length given by \fImaxPixels\fR; otherwise, a character must fit completely to be considered. \fBTK_WHOLE_WORDS\fR means stop on a word boundary, if possible. If \fBTK_AT_LEAST_ONE\fR is set, it means return at least one character even if no characters could fit in the length given by \fImaxPixels\fR. If \fBTK_AT_LEAST_ONE\fR is set and \fBTK_WHOLE_WORDS\fR 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. .AP int *lengthPtr out Filled with the number of pixels occupied by the number of characters returned as the result of \fBTk_MeasureChars\fR. .AP Display *display in Display on which to draw. .AP Drawable drawable in Window or pixmap in which to draw. .AP GC gc in Graphics context for drawing characters. The font selected into this GC must be the same as the \fItkfont\fR. .AP int "x, y" in Coordinates at which to place the left edge of the baseline when displaying \fIstring\fR. .AP int firstByte in The index of the first byte of the first character to underline in the \fIstring\fR. Underlining begins at the left edge of this character. .AP int lastByte in The index of the first byte of the last character up to which the underline will be drawn. The character specified by \fIlastByte\fR will not itself be underlined. .BE .SH DESCRIPTION .PP 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 \fBTk_ComputeTextLayout\fR. 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. Note that the interfaces described here are byte-oriented not character-oriented, so index values coming from Tcl scripts need to be converted to byte offsets using the \fBTcl_UtfAtIndex\fR and related routines. .PP 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 \fBTk_ComputeTextLayout\fR for a programming interface that supports the platform-independent expansion of tab characters into columns and newlines/returns into multi-line text. .PP \fBTk_MeasureChars\fR 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 bytes from \fIstring\fR that fit in the space specified by \fImaxPixels\fR subject to the conditions described by \fIflags\fR. If all characters fit, the return value will be \fInumBytes\fR. \fI*lengthPtr\fR 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 \fI*lengthPtr\fR is filled with the distance between the left edge of \fIstring\fR[0] and the right edge of \fIstring\fR[4]. .PP \fBTk_TextWidth\fR is a wrapper function that provides a simpler interface to the \fBTk_MeasureChars\fR function. The return value is how much space in pixels the given \fIstring\fR needs. .PP \fBTk_DrawChars\fR draws the \fIstring\fR at the given location in the given \fIdrawable\fR. .PP \fBTk_UnderlineChars\fR underlines the given range of characters in the given \fIstring\fR. It does not draw the characters (which are assumed to have been displayed previously by \fBTk_DrawChars\fR); 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. .SH KEYWORDS font