src/frontends/qt4/GuiWorkArea.cpp

   1 /**
   2  * \file GuiWorkArea.cpp
   3  * This file is part of LyX, the document processor.
   4  * Licence details can be found in the file COPYING.
   5  *
   6  * \author John Levon
   7  * \author Abdelrazak Younes
   8  *
   9  * Full author contact details are available in file CREDITS.
  10  */
  11
  12 #include <config.h>
  13
  14 #include "GuiWorkArea.h"
  15
  16 #include "GuiApplication.h"
  17 #include "QLPainter.h"
  18 #include "QKeySymbol.h"
  19 #include "qt_helpers.h"
  20
  21 #include "frontends/LyXView.h"
  22
  23 #include "BufferView.h"
  24 #include "Color.h"
  25 #include "debug.h"
  26 #include "FuncRequest.h"
  27 #include "LyXRC.h"
  28 #include "rowpainter.h"
  29 #include "version.h"
  30
  31 #include "support/filetools.h" // LibFileSearch
  32 #include "support/convert.h"
  33
  34 #include "graphics/GraphicsImage.h"
  35 #include "graphics/GraphicsLoader.h"
  36
  37 #include <QInputContext>
  38 #include <QLayout>
  39 #include <QMainWindow>
  40 #include <QPainter>
  41 #include <QScrollBar>
  42 #include <QTimer>
  43
  44 #include <boost/bind.hpp>
  45 #include <boost/current_function.hpp>
  46
  47 #ifdef Q_WS_X11
  48 #include <QX11Info>
  49 extern "C" int XEventsQueued(Display *display, int mode);
  50 #endif
  51
  52 #ifdef Q_WS_WIN
  53 int const CursorWidth = 2;
  54 #else
  55 int const CursorWidth = 1;
  56 #endif
  57
  58
  59 using std::endl;
  60 using std::string;
  61
  62 namespace lyx {
  63
  64 using support::FileName;
  65
  66 /// return the LyX mouse button state from Qt's
  67 static mouse_button::state q_button_state(Qt::MouseButton button)
  68 {
  69         mouse_button::state b = mouse_button::none;
  70         switch (button) {
  71                 case Qt::LeftButton:
  72                         b = mouse_button::button1;
  73                         break;
  74                 case Qt::MidButton:
  75                         b = mouse_button::button2;
  76                         break;
  77                 case Qt::RightButton:
  78                         b = mouse_button::button3;
  79                         break;
  80                 default:
  81                         break;
  82         }
  83         return b;
  84 }
  85
  86
  87 /// return the LyX mouse button state from Qt's
  88 mouse_button::state q_motion_state(Qt::MouseButtons state)
  89 {
  90         mouse_button::state b = mouse_button::none;
  91         if (state & Qt::LeftButton)
  92                 b |= mouse_button::button1;
  93         if (state & Qt::MidButton)
  94                 b |= mouse_button::button2;
  95         if (state & Qt::RightButton)
  96                 b |= mouse_button::button3;
  97         return b;
  98 }
  99
 100
 101 namespace frontend {
 102
 103 class CursorWidget {
 104 public:
 105         CursorWidget() {}
 106
 107         void draw(QPainter & painter)
 108         {
 109                 if (show_ && rect_.isValid()) {
 110                         switch (shape_) {
 111                         case L_SHAPE:
 112                                 painter.fillRect(rect_.x(), rect_.y(), CursorWidth, rect_.height(), color_);
 113                                 painter.setPen(color_);
 114                                 painter.drawLine(rect_.bottomLeft().x() + CursorWidth, rect_.bottomLeft().y(),
 115                                                                                                  rect_.bottomRight().x(), rect_.bottomLeft().y());
 116                                 break;
 117
 118                         case REVERSED_L_SHAPE:
 119                                 painter.fillRect(rect_.x() + rect_.height() / 3, rect_.y(), CursorWidth, rect_.height(), color_);
 120                                 painter.setPen(color_);
 121                                 painter.drawLine(rect_.bottomRight().x() - CursorWidth, rect_.bottomLeft().y(),
 122                                                                                                          rect_.bottomLeft().x(), rect_.bottomLeft().y());
 123                                 break;
 124
 125                         default:
 126                                 painter.fillRect(rect_, color_);
 127                                 break;
 128                         }
 129                 }
 130         }
 131
 132         void update(int x, int y, int h, CursorShape shape)
 133         {
 134                 color_ = guiApp->colorCache().get(Color::cursor);
 135                 shape_ = shape;
 136                 switch (shape) {
 137                 case L_SHAPE:
 138                         rect_ = QRect(x, y, CursorWidth + h / 3, h);
 139                         break;
 140                 case REVERSED_L_SHAPE:
 141                         rect_ = QRect(x - h / 3, y, CursorWidth + h / 3, h);
 142                         break;
 143                 default:
 144                         rect_ = QRect(x, y, CursorWidth, h);
 145                         break;
 146                 }
 147         }
 148
 149         void show(bool set_show = true) { show_ = set_show; }
 150         void hide() { show_ = false; }
 151
 152         QRect const & rect() { return rect_; }
 153
 154 private:
 155         ///
 156         CursorShape shape_;
 157         ///
 158         bool show_;
 159         ///
 160         QColor color_;
 161         ///
 162         QRect rect_;
 163 };
 164
 165
 166 // This is a 'heartbeat' generating synthetic mouse move events when the
 167 // cursor is at the top or bottom edge of the viewport. One scroll per 0.2 s
 168 SyntheticMouseEvent::SyntheticMouseEvent()
 169         : timeout(200), restart_timeout(true),
 170           x_old(-1), y_old(-1), scrollbar_value_old(-1.0)
 171 {}
 172
 173
 174 GuiWorkArea::GuiWorkArea(int w, int h, int id, LyXView & lyx_view)
 175         : WorkArea(id, lyx_view), need_resize_(false), schedule_redraw_(false),
 176           preedit_lines_(1)
 177 {
 178         screen_ = QPixmap(viewport()->width(), viewport()->height());
 179         cursor_ = new frontend::CursorWidget();
 180         cursor_->hide();
 181
 182         setVerticalScrollBarPolicy(Qt::ScrollBarAsNeeded);
 183         setHorizontalScrollBarPolicy(Qt::ScrollBarAlwaysOff);
 184         setAcceptDrops(true);
 185         setMouseTracking(true);
 186         setMinimumSize(100, 70);
 187
 188         viewport()->setAutoFillBackground(false);
 189         // We don't need double-buffering nor SystemBackground on
 190         // the viewport because we have our own backing pixmap.
 191         viewport()->setAttribute(Qt::WA_NoSystemBackground);
 192
 193         setFocusPolicy(Qt::WheelFocus);
 194
 195         viewport()->setCursor(Qt::IBeamCursor);
 196
 197         resize(w, h);
 198
 199         synthetic_mouse_event_.timeout.timeout.connect(
 200                 boost::bind(&GuiWorkArea::generateSyntheticMouseEvent,
 201                             this));
 202
 203         // Initialize the vertical Scroll Bar
 204         QObject::connect(verticalScrollBar(), SIGNAL(actionTriggered(int)),
 205                 this, SLOT(adjustViewWithScrollBar(int)));
 206
 207         // disable context menu for the scrollbar
 208         verticalScrollBar()->setContextMenuPolicy(Qt::NoContextMenu);
 209
 210         // PageStep only depends on the viewport height.
 211         verticalScrollBar()->setPageStep(viewport()->height());
 212
 213         LYXERR(Debug::GUI) << BOOST_CURRENT_FUNCTION
 214                 << "\n Area width\t" << width()
 215                 << "\n Area height\t" << height()
 216                 << "\n viewport width\t" << viewport()->width()
 217                 << "\n viewport height\t" << viewport()->height()
 218                 << endl;
 219
 220         // Enables input methods for asian languages.
 221         // Must be set when creating custom text editing widgets.
 222         setAttribute(Qt::WA_InputMethodEnabled, true);
 223 }
 224
 225
 226 void GuiWorkArea::setScrollbarParams(int h, int scroll_pos, int scroll_line_step)
 227 {
 228         if (verticalScrollBarPolicy() != Qt::ScrollBarAlwaysOn)
 229                 setVerticalScrollBarPolicy(Qt::ScrollBarAlwaysOn);
 230
 231         verticalScrollBar()->setTracking(false);
 232
 233         // do what cursor movement does (some grey)
 234         h += height() / 4;
 235         int scroll_max_ = std::max(0, h - height());
 236
 237         verticalScrollBar()->setRange(0, scroll_max_);
 238         verticalScrollBar()->setSliderPosition(scroll_pos);
 239         verticalScrollBar()->setSingleStep(scroll_line_step);
 240         verticalScrollBar()->setValue(scroll_pos);
 241
 242         verticalScrollBar()->setTracking(true);
 243 }
 244
 245
 246 void GuiWorkArea::adjustViewWithScrollBar(int)
 247 {
 248         scrollBufferView(verticalScrollBar()->sliderPosition());
 249         QApplication::syncX();
 250 }
 251
 252
 253 void GuiWorkArea::focusInEvent(QFocusEvent * /*event*/)
 254 {
 255         // No need to do anything if we didn't change views...
 256 //      if (theApp() == 0 || &lyx_view_ == theApp()->currentView())
 257 //              return;
 258
 259         theApp()->setCurrentView(lyx_view_);
 260
 261         // Repaint the whole screen.
 262         // Note: this is different from redraw() as only the backing pixmap
 263         // will be redrawn, which is cheap.
 264         viewport()->repaint();
 265
 266         // FIXME: it would be better to send a signal "newBuffer()"
 267         // in BufferList that could be connected to the different tabbars.
 268         lyx_view_.updateTab();
 269
 270         startBlinkingCursor();
 271 }
 272
 273
 274 void GuiWorkArea::focusOutEvent(QFocusEvent * /*event*/)
 275 {
 276         stopBlinkingCursor();
 277 }
 278
 279
 280 void GuiWorkArea::mousePressEvent(QMouseEvent * e)
 281 {
 282         if (dc_event_.active && dc_event_ == *e) {
 283                 dc_event_.active = false;
 284                 FuncRequest cmd(LFUN_MOUSE_TRIPLE,
 285                         e->x(), e->y(),
 286                         q_button_state(e->button()));
 287                 dispatch(cmd);
 288                 return;
 289         }
 290
 291         inputContext()->reset();
 292
 293         FuncRequest const cmd(LFUN_MOUSE_PRESS, e->x(), e->y(),
 294                 q_button_state(e->button()));
 295         dispatch(cmd, q_key_state(e->modifiers()));
 296 }
 297
 298
 299 void GuiWorkArea::mouseReleaseEvent(QMouseEvent * e)
 300 {
 301         if (synthetic_mouse_event_.timeout.running())
 302                 synthetic_mouse_event_.timeout.stop();
 303
 304         FuncRequest const cmd(LFUN_MOUSE_RELEASE, e->x(), e->y(),
 305                               q_button_state(e->button()));
 306         dispatch(cmd);
 307 }
 308
 309
 310 void GuiWorkArea::mouseMoveEvent(QMouseEvent * e)
 311 {
 312         // we kill the triple click if we move
 313         doubleClickTimeout();
 314         FuncRequest cmd(LFUN_MOUSE_MOTION, e->x(), e->y(),
 315                               q_motion_state(e->buttons()));
 316
 317         // If we're above or below the work area...
 318         if (e->y() <= 20 || e->y() >= viewport()->height() - 20) {
 319                 // Make sure only a synthetic event can cause a page scroll,
 320                 // so they come at a steady rate:
 321                 if (e->y() <= 20)
 322                         // _Force_ a scroll up:
 323                         cmd.y = -40;
 324                 else
 325                         cmd.y = viewport()->height();
 326                 // Store the event, to be handled when the timeout expires.
 327                 synthetic_mouse_event_.cmd = cmd;
 328
 329                 if (synthetic_mouse_event_.timeout.running())
 330                         // Discard the event. Note that it _may_ be handled
 331                         // when the timeout expires if
 332                         // synthetic_mouse_event_.cmd has not been overwritten.
 333                         // Ie, when the timeout expires, we handle the
 334                         // most recent event but discard all others that
 335                         // occurred after the one used to start the timeout
 336                         // in the first place.
 337                         return;
 338                 else {
 339                         synthetic_mouse_event_.restart_timeout = true;
 340                         synthetic_mouse_event_.timeout.start();
 341                         // Fall through to handle this event...
 342                 }
 343
 344         } else if (synthetic_mouse_event_.timeout.running()) {
 345                 // Store the event, to be possibly handled when the timeout
 346                 // expires.
 347                 // Once the timeout has expired, normal control is returned
 348                 // to mouseMoveEvent (restart_timeout = false).
 349                 // This results in a much smoother 'feel' when moving the
 350                 // mouse back into the work area.
 351                 synthetic_mouse_event_.cmd = cmd;
 352                 synthetic_mouse_event_.restart_timeout = false;
 353                 return;
 354         }
 355
 356         // Has anything changed on-screen since the last QMouseEvent
 357         // was received?
 358         double const scrollbar_value = verticalScrollBar()->value();
 359         if (e->x() != synthetic_mouse_event_.x_old ||
 360             e->y() != synthetic_mouse_event_.y_old ||
 361             scrollbar_value != synthetic_mouse_event_.scrollbar_value_old) {
 362                 // Yes it has. Store the params used to check this.
 363                 synthetic_mouse_event_.x_old = e->x();
 364                 synthetic_mouse_event_.y_old = e->y();
 365                 synthetic_mouse_event_.scrollbar_value_old = scrollbar_value;
 366
 367                 // ... and dispatch the event to the LyX core.
 368                 dispatch(cmd);
 369         }
 370 }
 371
 372
 373 void GuiWorkArea::wheelEvent(QWheelEvent * e)
 374 {
 375         // Wheel rotation by one notch results in a delta() of 120 (see
 376         // documentation of QWheelEvent)
 377         int const lines = qApp->wheelScrollLines() * e->delta() / 120;
 378         verticalScrollBar()->setValue(verticalScrollBar()->value() -
 379                         lines *  verticalScrollBar()->singleStep());
 380         adjustViewWithScrollBar();
 381 }
 382
 383
 384 void GuiWorkArea::generateSyntheticMouseEvent()
 385 {
 386 // Set things off to generate the _next_ 'pseudo' event.
 387         if (synthetic_mouse_event_.restart_timeout)
 388                 synthetic_mouse_event_.timeout.start();
 389
 390         // Has anything changed on-screen since the last timeout signal
 391         // was received?
 392         double const scrollbar_value = verticalScrollBar()->value();
 393         if (scrollbar_value != synthetic_mouse_event_.scrollbar_value_old) {
 394                 // Yes it has. Store the params used to check this.
 395                 synthetic_mouse_event_.scrollbar_value_old = scrollbar_value;
 396
 397                 // ... and dispatch the event to the LyX core.
 398                 dispatch(synthetic_mouse_event_.cmd);
 399         }
 400 }
 401
 402
 403 void GuiWorkArea::keyPressEvent(QKeyEvent * e)
 404 {
 405         // do nothing if there are other events
 406         // (the auto repeated events come too fast)
 407         // \todo FIXME: remove hard coded Qt keys, process the key binding
 408 #ifdef Q_WS_X11
 409         if (XEventsQueued(QX11Info::display(), 0) > 1 && e->isAutoRepeat()
 410                         && (Qt::Key_PageDown || Qt::Key_PageUp)) {
 411                 LYXERR(Debug::KEY)
 412                         << BOOST_CURRENT_FUNCTION << endl
 413                         << "system is busy: scroll key event ignored" << endl;
 414                 e->ignore();
 415                 return;
 416         }
 417 #endif
 418
 419         LYXERR(Debug::KEY) << BOOST_CURRENT_FUNCTION
 420                 << " count=" << e->count()
 421                 << " text=" << fromqstr(e->text())
 422                 << " isAutoRepeat=" << e->isAutoRepeat()
 423                 << " key=" << e->key()
 424                 << endl;
 425
 426         boost::shared_ptr<QKeySymbol> sym(new QKeySymbol);
 427         sym->set(e);
 428         processKeySym(sym, q_key_state(e->modifiers()));
 429 }
 430
 431 void GuiWorkArea::doubleClickTimeout() {
 432         dc_event_.active = false;
 433 }
 434
 435 void GuiWorkArea::mouseDoubleClickEvent(QMouseEvent * e)
 436 {
 437         dc_event_ = double_click(e);
 438         QTimer::singleShot(QApplication::doubleClickInterval(), this,
 439                            SLOT(doubleClickTimeout()));
 440         FuncRequest cmd(LFUN_MOUSE_DOUBLE,
 441                         e->x(), e->y(),
 442                         q_button_state(e->button()));
 443         dispatch(cmd);
 444 }
 445
 446
 447 void GuiWorkArea::resizeEvent(QResizeEvent * ev)
 448 {
 449         QAbstractScrollArea::resizeEvent(ev);
 450         need_resize_ = true;
 451 }
 452
 453
 454 void GuiWorkArea::update(int x, int y, int w, int h)
 455 {
 456         viewport()->repaint(x, y, w, h);
 457 }
 458
 459
 460 void GuiWorkArea::doGreyOut(QLPainter & pain)
 461 {
 462         pain.fillRectangle(0, 0, width(), height(),
 463                 Color::bottomarea);
 464
 465         //if (!lyxrc.show_banner)
 466         //      return;
 467         LYXERR(Debug::GUI) << "show banner: " << lyxrc.show_banner << endl;
 468         /// The text to be written on top of the pixmap
 469         QString const text = lyx_version ? QString(lyx_version) : qt_("unknown version");
 470         FileName const file = support::libFileSearch("images", "banner", "png");
 471         if (file.empty())
 472                 return;
 473
 474         QPixmap pm(toqstr(file.absFilename()));
 475         if (!pm) {
 476                 lyxerr << "could not load splash screen: '" << file << "'" << endl;
 477                 return;
 478         }
 479
 480         QFont font;
 481         // The font used to display the version info
 482         font.setStyleHint(QFont::SansSerif);
 483         font.setWeight(QFont::Bold);
 484         font.setPointSize(convert<int>(lyxrc.font_sizes[Font::SIZE_LARGE]));
 485
 486         int const w = pm.width();
 487         int const h = pm.height();
 488
 489         int x = (width() - w) / 2;
 490         int y = (height() - h) / 2;
 491
 492         pain.drawPixmap(x, y, pm);
 493
 494         x += 260;
 495         y += 270;
 496
 497         pain.setPen(QColor(255, 255, 0));
 498         pain.setFont(font);
 499         pain.drawText(x, y, text);
 500 }
 501
 502
 503 void GuiWorkArea::paintEvent(QPaintEvent * ev)
 504 {
 505         QRect const rc = ev->rect();
 506         /*
 507         LYXERR(Debug::PAINTING) << "paintEvent begin: x: " << rc.x()
 508                 << " y: " << rc.y()
 509                 << " w: " << rc.width()
 510                 << " h: " << rc.height() << endl;
 511         */
 512
 513         if (need_resize_) {
 514                 verticalScrollBar()->setPageStep(viewport()->height());
 515                 screen_ = QPixmap(viewport()->width(), viewport()->height());
 516                 resizeBufferView();
 517                 updateScreen();
 518                 WorkArea::hideCursor();
 519                 WorkArea::showCursor();
 520                 need_resize_ = false;
 521         }
 522
 523         QPainter pain(viewport());
 524         pain.drawPixmap(rc, screen_, rc);
 525         cursor_->draw(pain);
 526 }
 527
 528
 529 void GuiWorkArea::expose(int x, int y, int w, int h)
 530 {
 531         updateScreen();
 532         update(x, y, w, h);
 533 }
 534
 535
 536 void GuiWorkArea::updateScreen()
 537 {
 538         QLPainter pain(&screen_);
 539
 540         if (greyed_out_) {
 541                 LYXERR(Debug::GUI) << "splash screen requested" << endl;
 542                 verticalScrollBar()->hide();
 543                 doGreyOut(pain);
 544                 return;
 545         }
 546
 547         verticalScrollBar()->show();
 548         paintText(*buffer_view_, pain);
 549 }
 550
 551
 552 void GuiWorkArea::showCursor(int x, int y, int h, CursorShape shape)
 553 {
 554         if (schedule_redraw_) {
 555                 if (buffer_view_ && buffer_view_->buffer()) {
 556                         buffer_view_->update(Update::Force);
 557                         updateScreen();
 558                         viewport()->update(QRect(0, 0, viewport()->width(), viewport()->height()));
 559                 }
 560                 schedule_redraw_ = false;
 561                 // Show the cursor immediately after the update.
 562                 hideCursor();
 563                 toggleCursor();
 564                 return;
 565         }
 566
 567         cursor_->update(x, y, h, shape);
 568         cursor_->show();
 569         viewport()->update(cursor_->rect());
 570 }
 571
 572
 573 void GuiWorkArea::removeCursor()
 574 {
 575         cursor_->hide();
 576         //if (!qApp->focusWidget())
 577                 viewport()->update(cursor_->rect());
 578 }
 579
 580
 581 void GuiWorkArea::inputMethodEvent(QInputMethodEvent * e)
 582 {
 583         QString const & commit_string = e->commitString();
 584         docstring const & preedit_string
 585                 = qstring_to_ucs4(e->preeditString());
 586
 587         if(greyed_out_) {
 588                 e->ignore();
 589                 return;
 590         }
 591
 592         if (!commit_string.isEmpty()) {
 593
 594                 LYXERR(Debug::KEY) << BOOST_CURRENT_FUNCTION
 595                         << " preeditString =" << fromqstr(e->preeditString())
 596                         << " commitString  =" << fromqstr(e->commitString())
 597                         << endl;
 598
 599                 int key = 0;
 600
 601                 // FIXME Iwami 04/01/07: we should take care also of UTF16 surrogates here.
 602                 for (int i = 0; i < commit_string.size(); ++i) {
 603                         QKeyEvent ev(QEvent::KeyPress, key, Qt::NoModifier, commit_string[i]);
 604                         keyPressEvent(&ev);
 605                 }
 606         }
 607
 608         // Hide the cursor during the kana-kanji transformation.
 609         if (preedit_string.empty())
 610                 startBlinkingCursor();
 611         else
 612                 stopBlinkingCursor();
 613
 614         // last_width : for checking if last preedit string was/wasn't empty.
 615         static bool last_width = false;
 616         if (!last_width && preedit_string.empty()) {
 617                 // if last_width is last length of preedit string.
 618                 e->accept();
 619                 return;
 620         }
 621
 622         QLPainter pain(&screen_);
 623         buffer_view_->updateMetrics(false);
 624         paintText(*buffer_view_, pain);
 625         Font font = buffer_view_->cursor().getFont();
 626         FontMetrics const & fm = theFontMetrics(font);
 627         int height = fm.maxHeight();
 628         int cur_x = cursor_->rect().left();
 629         int cur_y = cursor_->rect().bottom();
 630
 631         // redraw area of preedit string.
 632         update(0, cur_y - height, GuiWorkArea::width(),
 633                 (height + 1) * preedit_lines_);
 634
 635         if (preedit_string.empty()) {
 636                 last_width = false;
 637                 preedit_lines_ = 1;
 638                 e->accept();
 639                 return;
 640         }
 641         last_width = true;
 642
 643         // att : stores an IM attribute.
 644         QList<QInputMethodEvent::Attribute> const & att = e->attributes();
 645
 646         // get attributes of input method cursor.
 647         // cursor_pos : cursor position in preedit string.
 648         size_t cursor_pos = 0;
 649         bool cursor_is_visible = false;
 650         for (int i = 0; i < att.size(); ++i) {
 651                 if (att.at(i).type == QInputMethodEvent::Cursor) {
 652                         cursor_pos = att.at(i).start;
 653                         cursor_is_visible = att.at(i).length != 0;
 654                         break;
 655                 }
 656         }
 657
 658         size_t preedit_length = preedit_string.length();
 659
 660         // get position of selection in input method.
 661         // FIXME: isn't there a way to do this simplier?
 662         // rStart : cursor position in selected string in IM.
 663         size_t rStart = 0;
 664         // rLength : selected string length in IM.
 665         size_t rLength = 0;
 666         if (cursor_pos < preedit_length) {
 667                 for (int i = 0; i < att.size(); ++i) {
 668                         if (att.at(i).type == QInputMethodEvent::TextFormat) {
 669                                 if (att.at(i).start <= int(cursor_pos)
 670                                         && int(cursor_pos) < att.at(i).start + att.at(i).length) {
 671                                                 rStart = att.at(i).start;
 672                                                 rLength = att.at(i).length;
 673                                                 if (!cursor_is_visible)
 674                                                         cursor_pos += rLength;
 675                                                 break;
 676                                 }
 677                         }
 678                 }
 679         }
 680         else {
 681                 rStart = cursor_pos;
 682                 rLength = 0;
 683         }
 684
 685         int const right_margin = rightMargin();
 686         Painter::preedit_style ps;
 687         // Most often there would be only one line:
 688         preedit_lines_ = 1;
 689         for (size_t pos = 0; pos != preedit_length; ++pos) {
 690                 char_type const typed_char = preedit_string[pos];
 691                 // reset preedit string style
 692                 ps = Painter::preedit_default;
 693
 694                 // if we reached the right extremity of the screen, go to next line.
 695                 if (cur_x + fm.width(typed_char) > GuiWorkArea::width() - right_margin) {
 696                         cur_x = right_margin;
 697                         cur_y += height + 1;
 698                         ++preedit_lines_;
 699                 }
 700                 // preedit strings are displayed with dashed underline
 701                 // and partial strings are displayed white on black indicating
 702                 // that we are in selecting mode in the input method.
 703                 // FIXME: rLength == preedit_length is not a changing condition
 704                 // FIXME: should be put out of the loop.
 705                 if (pos >= rStart
 706                         && pos < rStart + rLength
 707                         && !(cursor_pos < rLength && rLength == preedit_length))
 708                         ps = Painter::preedit_selecting;
 709
 710                 if (pos == cursor_pos
 711                         && (cursor_pos < rLength && rLength == preedit_length))
 712                         ps = Painter::preedit_cursor;
 713
 714                 // draw one character and update cur_x.
 715                 cur_x += pain.preeditText(cur_x, cur_y, typed_char, font, ps);
 716         }
 717
 718         // update the preedit string screen area.
 719         update(0, cur_y - preedit_lines_*height, GuiWorkArea::width(),
 720                 (height + 1) * preedit_lines_);
 721
 722         // Don't forget to accept the event!
 723         e->accept();
 724 }
 725
 726
 727 QVariant GuiWorkArea::inputMethodQuery(Qt::InputMethodQuery query) const
 728 {
 729         QRect cur_r(0,0,0,0);
 730         switch (query) {
 731                 // this is the CJK-specific composition window position.
 732                 case Qt::ImMicroFocus:
 733                         cur_r = cursor_->rect();
 734                         if (preedit_lines_ != 1)
 735                                 cur_r.moveLeft(10);
 736                         cur_r.moveBottom(cur_r.bottom() + cur_r.height() * preedit_lines_);
 737                         // return lower right of cursor in LyX.
 738                         return cur_r;
 739                 default:
 740                         return QWidget::inputMethodQuery(query);
 741         }
 742 }
 743
 744 } // namespace frontend
 745 } // namespace lyx
 746
 747 #include "GuiWorkArea_moc.cpp"