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'\" Copyright (c) 1996 Sun Microsystems, Inc.
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'\" See the file "license.terms" for information on usage and redistribution
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'\" of this file, and for a DISCLAIMER OF ALL WARRANTIES.
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'\" RCS: @(#) $Id: MeasureChar.3,v 1.2 1998/09/14 18:22:52 stanton Exp $
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.TH Tk_MeasureChars 3 "" Tk "Tk Library Procedures"
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Tk_MeasureChars, Tk_TextWidth, Tk_DrawChars, Tk_UnderlineChars \- routines to measure and display simple single-line strings.
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\fBTk_MeasureChars(\fItkfont, string, maxChars, maxPixels, flags, lengthPtr\fB)\fR
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\fBTk_TextWidth(\fItkfont, string, numChars\fB)\fR
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\fBTk_DrawChars(\fIdisplay, drawable, gc, tkfont, string, numChars, x, y\fB)\fR
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\fBTk_UnderlineChars(\fIdisplay, drawable, gc, tkfont, string, x, y, firstChar, lastChar\fB)\fR
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.AS "const char" firstChar
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Token for font in which text is to be drawn or measured. Must have been
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returned by a previous call to \fBTk_GetFont\fR.
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.AP "const char" *string in
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Text to be measured or displayed. Need not be null terminated. Any
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non-printing meta-characters in the string (such as tabs, newlines, and
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other control characters) will be measured or displayed in a
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platform-dependent manner.
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The maximum number of characters to consider when measuring \fIstring\fR.
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Must be greater than or equal to 0.
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If \fImaxPixels\fR is greater than 0, it specifies the longest permissible
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line length in pixels. Characters from \fIstring\fR are processed only
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until this many pixels have been covered. If \fImaxPixels\fR is <= 0, then
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the line length is unbounded and the \fIflags\fR argument is ignored.
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Various flag bits OR-ed together: TK_PARTIAL_OK means include a character
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as long as any part of it fits in the length given by \fImaxPixels\fR;
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otherwise, a character must fit completely to be considered.
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TK_WHOLE_WORDS means stop on a word boundary, if possible. If
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TK_AT_LEAST_ONE is set, it means return at least one character even if no
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characters could fit in the length given by \fImaxPixels\fR. If
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TK_AT_LEAST_ONE is set and TK_WHOLE_WORDS is also set, it means that if
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not even one word fits on the line, return the first few letters of the
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word that did fit; if not even one letter of the word fit, then the first
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letter will still be returned.
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.AP int *lengthPtr out
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Filled with the number of pixels occupied by the number of characters
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returned as the result of \fBTk_MeasureChars\fR.
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The total number of characters to measure or draw from \fIstring\fR. Must
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be greater than or equal to 0.
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.AP Display *display in
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Display on which to draw.
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.AP Drawable drawable in
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Window or pixmap in which to draw.
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Graphics context for drawing characters. The font selected into this GC
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must be the same as the \fItkfont\fR.
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Coordinates at which to place the left edge of the baseline when displaying
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The index of the first character to underline in the \fIstring\fR.
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Underlining begins at the left edge of this character.
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The index of the last character up to which the underline will
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be drawn. The character specified by \fIlastChar\fR will not itself be
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These routines are for measuring and displaying simple single-font,
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single-line, strings. To measure and display single-font, multi-line,
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justified text, refer to the documentation for \fBTk_ComputeTextLayout\fR.
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There is no programming interface in the core of Tk that supports
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multi-font, multi-line text; support for that behavior must be built on
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top of simpler layers.
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A glyph is the displayable picture of a letter, number, or some other
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symbol. Not all character codes in a given font have a glyph.
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Characters such as tabs, newlines/returns, and control characters that
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have no glyph are measured and displayed by these procedures in a
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platform-dependent manner; under X, they are replaced with backslashed
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escape sequences, while under Windows and Macintosh hollow or solid boxes
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may be substituted. Refer to the documentation for
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\fBTk_ComputeTextLayout\fR for a programming interface that supports the
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platform-independent expansion of tab characters into columns and
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newlines/returns into multi-line text.
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\fBTk_MeasureChars\fR is used both to compute the length of a given
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string and to compute how many characters from a string fit in a given
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amount of space. The return value is the number of characters from
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\fIstring\fR that fit in the space specified by \fImaxPixels\fR subject to
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the conditions described by \fIflags\fR. If all characters fit, the return
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value will be \fImaxChars\fR. \fI*lengthPtr\fR is filled with the computed
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width, in pixels, of the portion of the string that was measured. For
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example, if the return value is 5, then \fI*lengthPtr\fR is filled with the
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distance between the left edge of \fIstring\fR[0] and the right edge of
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\fBTk_TextWidth\fR is a wrapper function that provides a simpler interface
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to the \fBTk_MeasureChars\fR function. The return value is how much
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space in pixels the given \fIstring\fR needs.
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\fBTk_DrawChars\fR draws the \fIstring\fR at the given location in the
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given \fIdrawable\fR.
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\fBTk_UnderlineChars\fR underlines the given range of characters in the
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given \fIstring\fR. It doesn't draw the characters (which are assumed to
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have been displayed previously by \fBTk_DrawChars\fR); it just draws the
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underline. This procedure is used to underline a few characters without
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having to construct an underlined font. To produce natively underlined
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text, the appropriate underlined font should be constructed and used.
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doc/MeasureChar.3
