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| 7 | '\" RCS: @(#) $Id: MeasureChar.3,v 1.4 1999/12/21 23:54:17 hobbs Exp $ |
| 8 | '\" |
| 9 | '\" The definitions below are for supplemental macros used in Tcl/Tk |
| 10 | '\" manual entries. |
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| 72 | '\" # Set up traps and other miscellaneous stuff for Tcl/Tk man pages. |
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| 207 | .SH "STANDARD OPTIONS" |
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| 218 | See the \\fBoptions\\fR manual entry for details on the standard options. |
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| 225 | Command-Line Name: \\fB\\$1\\fR |
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| 244 | .. |
| 245 | .TH Tk_MeasureChars 3 8.1 Tk "Tk Library Procedures" |
| 246 | .BS |
| 247 | .SH NAME |
| 248 | Tk_MeasureChars, Tk_TextWidth, Tk_DrawChars, Tk_UnderlineChars \- routines to measure and display simple single-line strings. |
| 249 | .SH SYNOPSIS |
| 250 | .nf |
| 251 | \fB#include <tk.h>\fR |
| 252 | .sp |
| 253 | int |
| 254 | \fBTk_MeasureChars(\fItkfont, string, numBytes, maxPixels, flags, lengthPtr\fB)\fR |
| 255 | .sp |
| 256 | int |
| 257 | \fBTk_TextWidth(\fItkfont, string, numBytes\fB)\fR |
| 258 | .sp |
| 259 | void |
| 260 | \fBTk_DrawChars(\fIdisplay, drawable, gc, tkfont, string, numBytes, x, y\fB)\fR |
| 261 | .sp |
| 262 | void |
| 263 | \fBTk_UnderlineChars(\fIdisplay, drawable, gc, tkfont, string, x, y, firstByte, lastByte\fB)\fR |
| 264 | .sp |
| 265 | .SH ARGUMENTS |
| 266 | .AS "const char" firstChar |
| 267 | .AP Tk_Font tkfont in |
| 268 | Token for font in which text is to be drawn or measured. Must have been |
| 269 | returned by a previous call to \fBTk_GetFont\fR. |
| 270 | .AP "const char" *string in |
| 271 | Text to be measured or displayed. Need not be null terminated. Any |
| 272 | non-printing meta-characters in the string (such as tabs, newlines, and |
| 273 | other control characters) will be measured or displayed in a |
| 274 | platform-dependent manner. |
| 275 | .VS 8.1 |
| 276 | .AP int numBytes in |
| 277 | The maximum number of bytes to consider when measuring or drawing |
| 278 | \fIstring\fR. Must be greater than or equal to 0. |
| 279 | .VE 8.1 |
| 280 | .AP int maxPixels in |
| 281 | If \fImaxPixels\fR is >= 0, it specifies the longest permissible |
| 282 | line length in pixels. Characters from \fIstring\fR are processed only |
| 283 | until this many pixels have been covered. If \fImaxPixels\fR is < 0, then |
| 284 | the line length is unbounded and the \fIflags\fR argument is ignored. |
| 285 | .AP int flags in |
| 286 | Various flag bits OR-ed together: TK_PARTIAL_OK means include a character |
| 287 | as long as any part of it fits in the length given by \fImaxPixels\fR; |
| 288 | otherwise, a character must fit completely to be considered. |
| 289 | TK_WHOLE_WORDS means stop on a word boundary, if possible. If |
| 290 | TK_AT_LEAST_ONE is set, it means return at least one character even if no |
| 291 | characters could fit in the length given by \fImaxPixels\fR. If |
| 292 | TK_AT_LEAST_ONE is set and TK_WHOLE_WORDS is also set, it means that if |
| 293 | not even one word fits on the line, return the first few letters of the |
| 294 | word that did fit; if not even one letter of the word fit, then the first |
| 295 | letter will still be returned. |
| 296 | .AP int *lengthPtr out |
| 297 | Filled with the number of pixels occupied by the number of characters |
| 298 | returned as the result of \fBTk_MeasureChars\fR. |
| 299 | .AP Display *display in |
| 300 | Display on which to draw. |
| 301 | .AP Drawable drawable in |
| 302 | Window or pixmap in which to draw. |
| 303 | .AP GC gc in |
| 304 | Graphics context for drawing characters. The font selected into this GC |
| 305 | must be the same as the \fItkfont\fR. |
| 306 | .AP int "x, y" in |
| 307 | Coordinates at which to place the left edge of the baseline when displaying |
| 308 | \fIstring\fR. |
| 309 | .VS 8.1 |
| 310 | .AP int firstByte in |
| 311 | The index of the first byte of the first character to underline in the |
| 312 | \fIstring\fR. Underlining begins at the left edge of this character. |
| 313 | .AP int lastByte in |
| 314 | The index of the first byte of the last character up to which the |
| 315 | underline will be drawn. The character specified by \fIlastByte\fR |
| 316 | will not itself be underlined. |
| 317 | .VE 8.1 |
| 318 | .BE |
| 319 | |
| 320 | .SH DESCRIPTION |
| 321 | .PP |
| 322 | These routines are for measuring and displaying simple single-font, |
| 323 | single-line, strings. To measure and display single-font, multi-line, |
| 324 | justified text, refer to the documentation for \fBTk_ComputeTextLayout\fR. |
| 325 | There is no programming interface in the core of Tk that supports |
| 326 | multi-font, multi-line text; support for that behavior must be built on |
| 327 | top of simpler layers. |
| 328 | .VS 8.1 |
| 329 | Note that the interfaces described here are |
| 330 | byte-oriented not character-oriented, so index values coming from Tcl |
| 331 | scripts need to be converted to byte offsets using the |
| 332 | \fBTcl_UtfAtIndex\fR and related routines. |
| 333 | .VE 8.1 |
| 334 | .PP |
| 335 | A glyph is the displayable picture of a letter, number, or some other |
| 336 | symbol. Not all character codes in a given font have a glyph. |
| 337 | Characters such as tabs, newlines/returns, and control characters that |
| 338 | have no glyph are measured and displayed by these procedures in a |
| 339 | platform-dependent manner; under X, they are replaced with backslashed |
| 340 | escape sequences, while under Windows and Macintosh hollow or solid boxes |
| 341 | may be substituted. Refer to the documentation for |
| 342 | \fBTk_ComputeTextLayout\fR for a programming interface that supports the |
| 343 | platform-independent expansion of tab characters into columns and |
| 344 | newlines/returns into multi-line text. |
| 345 | .PP |
| 346 | \fBTk_MeasureChars\fR is used both to compute the length of a given |
| 347 | string and to compute how many characters from a string fit in a given |
| 348 | amount of space. The return value is the number of bytes from |
| 349 | \fIstring\fR that fit in the space specified by \fImaxPixels\fR subject to |
| 350 | the conditions described by \fIflags\fR. If all characters fit, the return |
| 351 | value will be \fInumBytes\fR. \fI*lengthPtr\fR is filled with the computed |
| 352 | width, in pixels, of the portion of the string that was measured. For |
| 353 | example, if the return value is 5, then \fI*lengthPtr\fR is filled with the |
| 354 | distance between the left edge of \fIstring\fR[0] and the right edge of |
| 355 | \fIstring\fR[4]. |
| 356 | .PP |
| 357 | \fBTk_TextWidth\fR is a wrapper function that provides a simpler interface |
| 358 | to the \fBTk_MeasureChars\fR function. The return value is how much |
| 359 | space in pixels the given \fIstring\fR needs. |
| 360 | .PP |
| 361 | \fBTk_DrawChars\fR draws the \fIstring\fR at the given location in the |
| 362 | given \fIdrawable\fR. |
| 363 | .PP |
| 364 | \fBTk_UnderlineChars\fR underlines the given range of characters in the |
| 365 | given \fIstring\fR. It doesn't draw the characters (which are assumed to |
| 366 | have been displayed previously by \fBTk_DrawChars\fR); it just draws the |
| 367 | underline. This procedure is used to underline a few characters without |
| 368 | having to construct an underlined font. To produce natively underlined |
| 369 | text, the appropriate underlined font should be constructed and used. |
| 370 | |
| 371 | .SH KEYWORDS |
| 372 | font |