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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 |
| 226 | Database Name: \\fB\\$2\\fR |
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| 243 | \\$1\l'|0\(ul'\\$2 |
| 244 | .. |
| 245 | .TH Tk_ComputeTextLayout 3 8.1 Tk "Tk Library Procedures" |
| 246 | .BS |
| 247 | .SH NAME |
| 248 | Tk_ComputeTextLayout, Tk_FreeTextLayout, Tk_DrawTextLayout, Tk_UnderlineTextLayout, Tk_PointToChar, Tk_CharBbox, Tk_DistanceToTextLayout, Tk_IntersectTextLayout, Tk_TextLayoutToPostscript \- routines to measure and display single-font, multi-line, justified text. |
| 249 | .SH SYNOPSIS |
| 250 | .nf |
| 251 | \fB#include <tk.h>\fR |
| 252 | .sp |
| 253 | Tk_TextLayout |
| 254 | \fBTk_ComputeTextLayout(\fItkfont, string, numChars, wrapLength, justify, flags, widthPtr, heightPtr\fB)\fR |
| 255 | .sp |
| 256 | void |
| 257 | \fBTk_FreeTextLayout(\fIlayout\fB)\fR |
| 258 | .sp |
| 259 | void |
| 260 | \fBTk_DrawTextLayout(\fIdisplay, drawable, gc, layout, x, y, firstChar, lastChar\fB)\fR |
| 261 | .sp |
| 262 | void |
| 263 | \fBTk_UnderlineTextLayout(\fIdisplay, drawable, gc, layout, x, y, underline\fB)\fR |
| 264 | .sp |
| 265 | int |
| 266 | \fBTk_PointToChar(\fIlayout, x, y\fB)\fR |
| 267 | .sp |
| 268 | int |
| 269 | \fBTk_CharBbox(\fIlayout, index, xPtr, yPtr, widthPtr, heightPtr\fB)\fR |
| 270 | .sp |
| 271 | int |
| 272 | \fBTk_DistanceToTextLayout(\fIlayout, x, y\fB)\fR |
| 273 | .sp |
| 274 | int |
| 275 | \fBTk_IntersectTextLayout(\fIlayout, x, y, width, height\fB)\fR |
| 276 | .sp |
| 277 | void |
| 278 | \fBTk_TextLayoutToPostscript(\fIinterp, layout\fB)\fR |
| 279 | |
| 280 | .SH ARGUMENTS |
| 281 | .AS Tk_TextLayout "*xPtr, *yPtr" |
| 282 | .AP Tk_Font tkfont in |
| 283 | Font to use when constructing and displaying a text layout. The |
| 284 | \fItkfont\fR must remain valid for the lifetime of the text layout. Must |
| 285 | have been returned by a previous call to \fBTk_GetFont\fR. |
| 286 | .AP "const char" *string in |
| 287 | Potentially multi-line string whose dimensions are to be computed and |
| 288 | stored in the text layout. The \fIstring\fR must remain valid for the |
| 289 | lifetime of the text layout. |
| 290 | .AP int numChars in |
| 291 | The number of characters to consider from \fIstring\fR. If |
| 292 | \fInumChars\fR is less than 0, then assumes \fIstring\fR is null |
| 293 | .VS 8.1 |
| 294 | terminated and uses \fBTcl_NumUtfChars\fR to determine the length of |
| 295 | \fIstring\fR. |
| 296 | .VE |
| 297 | .AP int wrapLength in |
| 298 | Longest permissible line length, in pixels. Lines in \fIstring\fR will |
| 299 | automatically be broken at word boundaries and wrapped when they reach |
| 300 | this length. If \fIwrapLength\fR is too small for even a single |
| 301 | character to fit on a line, it will be expanded to allow one character to |
| 302 | fit on each line. If \fIwrapLength\fR is <= 0, there is no automatic |
| 303 | wrapping; lines will get as long as they need to be and only wrap if a |
| 304 | newline/return character is encountered. |
| 305 | .AP Tk_Justify justify in |
| 306 | How to justify the lines in a multi-line text layout. Possible values |
| 307 | are TK_JUSTIFY_LEFT, TK_JUSTIFY_CENTER, or TK_JUSTIFY_RIGHT. If the text |
| 308 | layout only occupies a single line, then \fIjustify\fR is irrelevant. |
| 309 | .AP int flags in |
| 310 | Various flag bits OR-ed together. TK_IGNORE_TABS means that tab characters |
| 311 | should not be expanded to the next tab stop. TK_IGNORE_NEWLINES means that |
| 312 | newline/return characters should not cause a line break. If either tabs or |
| 313 | newlines/returns are ignored, then they will be treated as regular |
| 314 | characters, being measured and displayed in a platform-dependent manner as |
| 315 | described in \fBTk_MeasureChars\fR, and will not have any special behaviors. |
| 316 | .AP int *widthPtr out |
| 317 | If non-NULL, filled with either the width, in pixels, of the widest |
| 318 | line in the text layout, or the width, in pixels, of the bounding box for the |
| 319 | character specified by \fIindex\fR. |
| 320 | .AP int *heightPtr out |
| 321 | If non-NULL, filled with either the total height, in pixels, of all |
| 322 | the lines in the text layout, or the height, in pixels, of the bounding |
| 323 | box for the character specified by \fIindex\fR. |
| 324 | .AP Tk_TextLayout layout in |
| 325 | A token that represents the cached layout information about the single-font, |
| 326 | multi-line, justified piece of text. This token is returned by |
| 327 | \fBTk_ComputeTextLayout\fR. |
| 328 | .AP Display *display in |
| 329 | Display on which to draw. |
| 330 | .AP Drawable drawable in |
| 331 | Window or pixmap in which to draw. |
| 332 | .AP GC gc in |
| 333 | Graphics context to use for drawing text layout. The font selected in |
| 334 | this GC must correspond to the \fItkfont\fR used when constructing the |
| 335 | text layout. |
| 336 | .AP int "x, y" in |
| 337 | Point, in pixels, at which to place the upper-left hand corner of the |
| 338 | text layout when it is being drawn, or the coordinates of a point (with |
| 339 | respect to the upper-left hand corner of the text layout) to check |
| 340 | against the text layout. |
| 341 | .AP int firstChar in |
| 342 | The index of the first character to draw from the given text layout. |
| 343 | The number 0 means to draw from the beginning. |
| 344 | .AP int lastChar in |
| 345 | The index of the last character up to which to draw. The character |
| 346 | specified by \fIlastChar\fR itself will not be drawn. A number less |
| 347 | than 0 means to draw all characters in the text layout. |
| 348 | .AP int underline in |
| 349 | Index of the single character to underline in the text layout, or a number |
| 350 | less than 0 for no underline. |
| 351 | .AP int index in |
| 352 | The index of the character whose bounding box is desired. The bounding |
| 353 | box is computed with respect to the upper-left hand corner of the text layout. |
| 354 | .AP int "*xPtr, *yPtr" out |
| 355 | Filled with the upper-left hand corner, in pixels, of the bounding box |
| 356 | for the character specified by \fIindex\fR. Either or both \fIxPtr\fR |
| 357 | and \fIyPtr\fR may be NULL, in which case the corresponding value |
| 358 | is not calculated. |
| 359 | .AP int "width, height" in |
| 360 | Specifies the width and height, in pixels, of the rectangular area to |
| 361 | compare for intersection against the text layout. |
| 362 | .AP Tcl_Interp *interp out |
| 363 | Postscript code that will print the text layout is appended to |
| 364 | \fIinterp->result\fR. |
| 365 | .BE |
| 366 | |
| 367 | .SH DESCRIPTION |
| 368 | .PP |
| 369 | These routines are for measuring and displaying single-font, multi-line, |
| 370 | justified text. To measure and display simple single-font, single-line |
| 371 | strings, refer to the documentation for \fBTk_MeasureChars\fR. There is |
| 372 | no programming interface in the core of Tk that supports multi-font, |
| 373 | multi-line text; support for that behavior must be built on top of |
| 374 | simpler layers. |
| 375 | .VS 8.1 |
| 376 | Note that unlike the lower level text display routines, the functions |
| 377 | described here all operate on character-oriented lengths and indices |
| 378 | rather than byte-oriented values. See the description of |
| 379 | \fBTcl_UtfAtIndex\fR for more details on converting between character |
| 380 | and byte offsets. |
| 381 | .VE 8.1 |
| 382 | .PP |
| 383 | The routines described here are built on top of the programming interface |
| 384 | described in the \fBTk_MeasureChars\fR documentation. Tab characters and |
| 385 | newline/return characters may be treated specially by these procedures, |
| 386 | but all other characters are passed through to the lower level. |
| 387 | .PP |
| 388 | \fBTk_ComputeTextLayout\fR computes the layout information needed to |
| 389 | display a single-font, multi-line, justified \fIstring\fR of text and |
| 390 | returns a Tk_TextLayout token that holds this information. This token is |
| 391 | used in subsequent calls to procedures such as \fBTk_DrawTextLayout\fR, |
| 392 | \fBTk_DistanceToTextLayout\fR, and \fBTk_FreeTextLayout\fR. The |
| 393 | \fIstring\fR and \fItkfont\fR used when computing the layout must remain |
| 394 | valid for the lifetime of this token. |
| 395 | .PP |
| 396 | \fBTk_FreeTextLayout\fR is called to release the storage associated with |
| 397 | \fIlayout\fR when it is no longer needed. A \fIlayout\fR should not be used |
| 398 | in any other text layout procedures once it has been released. |
| 399 | .PP |
| 400 | \fBTk_DrawTextLayout\fR uses the information in \fIlayout\fR to display a |
| 401 | single-font, multi-line, justified string of text at the specified location. |
| 402 | .PP |
| 403 | \fBTk_UnderlineTextLayout\fR uses the information in \fIlayout\fR to |
| 404 | display an underline below an individual character. This procedure does |
| 405 | not draw the text, just the underline. To produce natively underlined |
| 406 | text, an underlined font should be constructed and used. All characters, |
| 407 | including tabs, newline/return characters, and spaces at the ends of |
| 408 | lines, can be underlined using this method. However, the underline will |
| 409 | never be drawn outside of the computed width of \fIlayout\fR; the |
| 410 | underline will stop at the edge for any character that would extend |
| 411 | partially outside of \fIlayout\fR, and the underline will not be visible |
| 412 | at all for any character that would be located completely outside of the |
| 413 | layout. |
| 414 | .PP |
| 415 | \fBTk_PointToChar\fR uses the information in \fIlayout\fR to determine the |
| 416 | character closest to the given point. The point is specified with respect |
| 417 | to the upper-left hand corner of the \fIlayout\fR, which is considered to be |
| 418 | located at (0, 0). Any point whose \fIy\fR-value is less that 0 will be |
| 419 | considered closest to the first character in the text layout; any point |
| 420 | whose \fIy\fR-value is greater than the height of the text layout will be |
| 421 | considered closest to the last character in the text layout. Any point |
| 422 | whose \fIx\fR-value is less than 0 will be considered closest to the first |
| 423 | character on that line; any point whose \fIx\fR-value is greater than the |
| 424 | width of the text layout will be considered closest to the last character on |
| 425 | that line. The return value is the index of the character that was closest |
| 426 | to the point. Given a \fIlayout\fR with no characters, the value 0 will |
| 427 | always be returned, referring to a hypothetical zero-width placeholder |
| 428 | character. |
| 429 | .PP |
| 430 | \fBTk_CharBbox\fR uses the information in \fIlayout\fR to return the |
| 431 | bounding box for the character specified by \fIindex\fR. The width of the |
| 432 | bounding box is the advance width of the character, and does not include any |
| 433 | left or right bearing. Any character that extends partially outside of |
| 434 | \fIlayout\fR is considered to be truncated at the edge. Any character |
| 435 | that would be located completely outside of \fIlayout\fR is considered to |
| 436 | be zero-width and pegged against the edge. The height of the bounding |
| 437 | box is the line height for this font, extending from the top of the |
| 438 | ascent to the bottom of the descent; information about the actual height |
| 439 | of individual letters is not available. For measurement purposes, a |
| 440 | \fIlayout\fR that contains no characters is considered to contain a |
| 441 | single zero-width placeholder character at index 0. If \fIindex\fR was |
| 442 | not a valid character index, the return value is 0 and \fI*xPtr\fR, |
| 443 | \fI*yPtr\fR, \fI*widthPtr\fR, and \fI*heightPtr\fR are unmodified. |
| 444 | Otherwise, if \fIindex\fR did specify a valid, the return value is |
| 445 | non-zero, and \fI*xPtr\fR, \fI*yPtr\fR, \fI*widthPtr\fR, and |
| 446 | \fI*heightPtr\fR are filled with the bounding box information for the |
| 447 | character. If any of \fIxPtr\fR, \fIyPtr\fR, \fIwidthPtr\fR, or |
| 448 | \fIheightPtr\fR are NULL, the corresponding value is not calculated or |
| 449 | stored. |
| 450 | .PP |
| 451 | \fBTk_DistanceToTextLayout\fR computes the shortest distance in pixels from |
| 452 | the given point (\fIx, y\fR) to the characters in \fIlayout\fR. |
| 453 | Newline/return characters and non-displaying space characters that occur at |
| 454 | the end of individual lines in the text layout are ignored for hit detection |
| 455 | purposes, but tab characters are not. The return value is 0 if the point |
| 456 | actually hits the \fIlayout\fR. If the point didn't hit the \fIlayout\fR |
| 457 | then the return value is the distance in pixels from the point to the |
| 458 | \fIlayout\fR. |
| 459 | .PP |
| 460 | \fBTk_IntersectTextLayout\fR determines whether a \fIlayout\fR lies |
| 461 | entirely inside, entirely outside, or overlaps a given rectangle. |
| 462 | Newline/return characters and non-displaying space characters that occur |
| 463 | at the end of individual lines in the \fIlayout\fR are ignored for |
| 464 | intersection calculations. The return value is \-1 if the \fIlayout\fR is |
| 465 | entirely outside of the rectangle, 0 if it overlaps, and 1 if it is |
| 466 | entirely inside of the rectangle. |
| 467 | .PP |
| 468 | \fBTk_TextLayoutToPostscript\fR outputs code consisting of a Postscript |
| 469 | array of strings that represent the individual lines in \fIlayout\fR. It |
| 470 | is the responsibility of the caller to take the Postscript array of |
| 471 | strings and add some Postscript function operate on the array to render |
| 472 | each of the lines. The code that represents the Postscript array of |
| 473 | strings is appended to \fIinterp->result\fR. |
| 474 | .PP |
| 475 | .SH DISPLAY MODEL |
| 476 | When measuring a text layout, space characters that occur at the end of a |
| 477 | line are ignored. The space characters still exist and the insertion point |
| 478 | can be positioned amongst them, but their additional width is ignored when |
| 479 | justifying lines or returning the total width of a text layout. All |
| 480 | end-of-line space characters are considered to be attached to the right edge |
| 481 | of the line; this behavior is logical for left-justified text and reasonable |
| 482 | for center-justified text, but not very useful when editing right-justified |
| 483 | text. Spaces are considered variable width characters; the first space that |
| 484 | extends past the edge of the text layout is clipped to the edge, and any |
| 485 | subsequent spaces on the line are considered zero width and pegged against |
| 486 | the edge. Space characters that occur in the middle of a line of text are |
| 487 | not suppressed and occupy their normal space width. |
| 488 | .PP |
| 489 | Tab characters are not ignored for measurement calculations. If wrapping |
| 490 | is turned on and there are enough tabs on a line, the next tab will wrap |
| 491 | to the beginning of the next line. There are some possible strange |
| 492 | interactions between tabs and justification; tab positions are calculated |
| 493 | and the line length computed in a left-justified world, and then the |
| 494 | whole resulting line is shifted so it is centered or right-justified, |
| 495 | causing the tab columns not to align any more. |
| 496 | .PP |
| 497 | When wrapping is turned on, lines may wrap at word breaks (space or tab |
| 498 | characters) or newline/returns. A dash or hyphen character in the middle |
| 499 | of a word is not considered a word break. \fBTk_ComputeTextLayout\fR |
| 500 | always attempts to place at least one word on each line. If it cannot |
| 501 | because the \fIwrapLength\fR is too small, the word will be broken and as |
| 502 | much as fits placed on the line and the rest on subsequent line(s). If |
| 503 | \fIwrapLength\fR is so small that not even one character can fit on a |
| 504 | given line, the \fIwrapLength\fR is ignored for that line and one |
| 505 | character will be placed on the line anyhow. When wrapping is turned |
| 506 | off, only newline/return characters may cause a line break. |
| 507 | .PP |
| 508 | When a text layout has been created using an underlined \fItkfont\fR, |
| 509 | then any space characters that occur at the end of individual lines, |
| 510 | newlines/returns, and tabs will not be displayed underlined when |
| 511 | \fBTk_DrawTextLayout\fR is called, because those characters are never |
| 512 | actually drawn \- they are merely placeholders maintained in the |
| 513 | \fIlayout\fR. |
| 514 | .SH KEYWORDS |
| 515 | font |