layout.cc

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/*
 * Dillo Widget
 *
 * Copyright 2005-2007 Sebastian Geerken <sgeerken@dillo.org>
 * Copyright 2024-2025 Rodrigo Arias Mallo <rodarima@gmail.com>
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation; either version 3 of the License, or
 * (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program.  If not, see <http://www.gnu.org/licenses/>.
 */
 
 
 
#include "core.hh"
 
#include "dlib/dlib.h"
#include "../lout/msg.h"
#include "../lout/debug.hh"
#include "../lout/misc.hh"
 
using namespace lout;
using namespace lout::container;
using namespace lout::object;
 
namespace dw {
namespace core {
 
bool Layout::LayoutImgRenderer::readyToDraw ()
{
   return true;
}
 
void Layout::LayoutImgRenderer::getBgArea (int *x, int *y, int *width,
                                           int *height)
{
   // TODO Actually not padding area, but visible area?
   getRefArea (x, y, width, height);
}
 
void Layout::LayoutImgRenderer::getRefArea (int *xRef, int *yRef, int *widthRef,
                                            int *heightRef)
{
   *xRef = 0;
   *yRef = 0;
   *widthRef = misc::max (layout->viewportWidth
                          - (layout->canvasHeightGreater ?
                             layout->vScrollbarThickness : 0),
                          layout->canvasWidth);
   *heightRef = misc::max (layout->viewportHeight
                           - layout->hScrollbarThickness,
                           layout->canvasAscent + layout->canvasDescent);
}
 
style::StyleImage *Layout::LayoutImgRenderer::getBackgroundImage ()
{
   return layout->bgImage;
}
 
style::BackgroundRepeat Layout::LayoutImgRenderer::getBackgroundRepeat ()
{
   return layout->bgRepeat;
}
 
style::BackgroundAttachment
   Layout::LayoutImgRenderer::getBackgroundAttachment ()
{
   return layout->bgAttachment;
}
 
style::Length Layout::LayoutImgRenderer::getBackgroundPositionX ()
{
   return layout->bgPositionX;
}
 
style::Length Layout::LayoutImgRenderer::getBackgroundPositionY ()
{
   return layout->bgPositionY;
}
 
void Layout::LayoutImgRenderer::draw (int x, int y, int width, int height)
{
   layout->queueDraw (x, y, width, height);
}
 
// ----------------------------------------------------------------------
 
void Layout::Receiver::resizeQueued (bool extremesChanged)
{
}
 
void Layout::Receiver::canvasSizeChanged (int width, int ascent, int descent)
{
}
 
// ----------------------------------------------------------------------
 
bool Layout::Emitter::emitToReceiver (lout::signal::Receiver *receiver,
                                      int signalNo, int argc,
                                      lout::object::Object **argv)
{
   Receiver *layoutReceiver = (Receiver*)receiver;
 
   switch (signalNo) {
   case CANVAS_SIZE_CHANGED:
      layoutReceiver->canvasSizeChanged (((Integer*)argv[0])->getValue (),
                                         ((Integer*)argv[1])->getValue (),
                                         ((Integer*)argv[2])->getValue ());
      break;
 
   case RESIZE_QUEUED:
      layoutReceiver->resizeQueued (((Boolean*)argv[0])->getValue ());
      break;
 
   default:
      misc::assertNotReached ();
   }
 
   return false;
}
 
void Layout::Emitter::emitResizeQueued (bool extremesChanged)
{
   Boolean ec (extremesChanged);
   Object *argv[1] = { &ec };
   emitVoid (RESIZE_QUEUED, 1, argv);
}
 
void Layout::Emitter::emitCanvasSizeChanged (int width,
                                             int ascent, int descent)
{
   Integer w (width), a (ascent), d (descent);
   Object *argv[3] = { &w, &a, &d };
   emitVoid (CANVAS_SIZE_CHANGED, 3, argv);
}
 
// ----------------------------------------------------------------------
 
bool Layout::LinkReceiver::enter (Widget *widget, int link, int img,
                                  int x, int y)
{
   return false;
}
 
bool Layout::LinkReceiver::press (Widget *widget, int link, int img,
                                  int x, int y, EventButton *event)
{
   return false;
}
 
bool Layout::LinkReceiver::release (Widget *widget, int link, int img,
                                    int x, int y, EventButton *event)
{
   return false;
}
 
bool Layout::LinkReceiver::click (Widget *widget, int link, int img,
                                    int x, int y, EventButton *event)
{
   return false;
}
 
// ----------------------------------------------------------------------
 
bool Layout::LinkEmitter::emitToReceiver (lout::signal::Receiver *receiver,
                                          int signalNo, int argc,
                                          lout::object::Object **argv)
{
   LinkReceiver *linkReceiver = (LinkReceiver*)receiver;
 
   switch (signalNo) {
   case ENTER:
      return linkReceiver->enter ((Widget*)argv[0],
                                  ((Integer*)argv[1])->getValue (),
                                  ((Integer*)argv[2])->getValue (),
                                  ((Integer*)argv[3])->getValue (),
                                  ((Integer*)argv[4])->getValue ());
 
   case PRESS:
      return linkReceiver->press ((Widget*)argv[0],
                                  ((Integer*)argv[1])->getValue (),
                                  ((Integer*)argv[2])->getValue (),
                                  ((Integer*)argv[3])->getValue (),
                                  ((Integer*)argv[4])->getValue (),
                                  (EventButton*)argv[5]);
 
   case RELEASE:
      return linkReceiver->release ((Widget*)argv[0],
                                    ((Integer*)argv[1])->getValue (),
                                    ((Integer*)argv[2])->getValue (),
                                    ((Integer*)argv[3])->getValue (),
                                    ((Integer*)argv[4])->getValue (),
                                    (EventButton*)argv[5]);
 
   case CLICK:
      return linkReceiver->click ((Widget*)argv[0],
                                  ((Integer*)argv[1])->getValue (),
                                  ((Integer*)argv[2])->getValue (),
                                  ((Integer*)argv[3])->getValue (),
                                  ((Integer*)argv[4])->getValue (),
                                  (EventButton*)argv[5]);
 
   default:
      misc::assertNotReached ();
   }
   return false;
}
 
bool Layout::LinkEmitter::emitEnter (Widget *widget, int link, int img,
                                     int x, int y)
{
   Integer ilink (link), iimg (img), ix (x), iy (y);
   Object *argv[5] = { widget, &ilink, &iimg, &ix, &iy };
   return emitBool (ENTER, 5, argv);
}
 
bool Layout::LinkEmitter::emitPress (Widget *widget, int link, int img,
                                     int x, int y, EventButton *event)
{
   Integer ilink (link), iimg (img), ix (x), iy (y);
   Object *argv[6] = { widget, &ilink, &iimg, &ix, &iy, event };
   return emitBool (PRESS, 6, argv);
}
 
bool Layout::LinkEmitter::emitRelease (Widget *widget, int link, int img,
                                       int x, int y, EventButton *event)
{
   Integer ilink (link), iimg (img), ix (x), iy (y);
   Object *argv[6] = { widget, &ilink, &iimg, &ix, &iy, event };
   return emitBool (RELEASE, 6, argv);
}
 
bool Layout::LinkEmitter::emitClick (Widget *widget, int link, int img,
                                     int x, int y, EventButton *event)
{
   Integer ilink (link), iimg (img), ix (x), iy (y);
   Object *argv[6] = { widget, &ilink, &iimg, &ix, &iy, event };
   return emitBool (CLICK, 6, argv);
}
 
// ---------------------------------------------------------------------
 
Layout::Anchor::~Anchor ()
{
   free(name);
}
 
// ---------------------------------------------------------------------
 
Layout::Layout (Platform *platform, bool limit)
{
   this->platform = platform;
   view = NULL;
   topLevel = NULL;
   widgetAtPoint = NULL;
 
   queueResizeList = new typed::Vector<Widget> (4, false);
 
   DBG_OBJ_CREATE ("dw::core::Layout");
 
   bgColor = NULL;
   bgImage = NULL;
   cursor = style::CURSOR_DEFAULT;
 
   canvasWidth = canvasAscent = canvasDescent = 0;
 
   usesViewport = false;
   drawAfterScrollReq = false;
   scrollX = scrollY = 0;
   viewportWidth = viewportHeight = 0;
   hScrollbarThickness = vScrollbarThickness = 0;
 
   DBG_OBJ_SET_NUM ("viewportWidth", viewportWidth);
   DBG_OBJ_SET_NUM ("viewportHeight", viewportHeight);
   DBG_OBJ_SET_NUM ("hScrollbarThickness", hScrollbarThickness);
   DBG_OBJ_SET_NUM ("vScrollbarThickness", vScrollbarThickness);
 
   requestedAnchor = NULL;
   scrollIdleId = -1;
   scrollIdleNotInterrupted = false;
 
   anchorsTable =
      new container::typed::HashTable <object::String, Anchor> (true, true);
 
   resizeIdleId = -1;
 
   textZone = new misc::ZoneAllocator (16 * 1024);
 
   DBG_OBJ_ASSOC_CHILD (&findtextState);
   DBG_OBJ_ASSOC_CHILD (&selectionState);
 
   platform->setLayout (this);
 
   selectionState.setLayout(this);
 
   queueResizeCounter = sizeAllocateCounter = sizeRequestCounter =
      getExtremesCounter = 0;
 
   layoutImgRenderer = NULL;
 
   resizeIdleCounter = queueResizeCounter = sizeAllocateCounter
      = sizeRequestCounter = getExtremesCounter = resizeCounter = 0;
   resizeLimit = limit;
}
 
Layout::~Layout ()
{
   widgetAtPoint = NULL;
 
   if (layoutImgRenderer) {
      if (bgImage)
         bgImage->removeExternalImgRenderer (layoutImgRenderer);
      delete layoutImgRenderer;
   }
 
   if (scrollIdleId != -1)
      platform->removeIdle (scrollIdleId);
   if (resizeIdleId != -1)
      platform->removeIdle (resizeIdleId);
   if (bgColor)
      bgColor->unref ();
   if (bgImage)
      bgImage->unref ();
   if (topLevel) {
      detachWidget (topLevel);
      Widget *w = topLevel;
      topLevel = NULL;
      delete w;
   }
 
   delete queueResizeList;
   delete platform;
   delete view;
   delete anchorsTable;
   delete textZone;
 
   if (requestedAnchor)
      free (requestedAnchor);
 
   DBG_OBJ_DELETE ();
}
 
void Layout::detachWidget (Widget *widget)
{
   // Called form ~Layout. Sometimes, the widgets (not only the toplevel widget)
   // do some stuff after the layout has been deleted, so *all* widgets have to
   // be detached, and check "layout != NULL" at relevant points.
 
   // Could be replaced by a virtual method in Widget, like getWidgetAtPoint,
   // if performance were really a problem.
 
   widget->layout = NULL;
   Iterator *it =
      widget->iterator ((Content::Type)
                        (Content::WIDGET_IN_FLOW | Content::WIDGET_OOF_CONT),
                        false);
   while (it->next ())
      detachWidget (it->getContent()->widget);
 
   it->unref ();
}
 
void Layout::addWidget (Widget *widget)
{
   if (topLevel) {
      MSG_WARN("widget already set\n");
      return;
   }
 
   // The toplevel widget always establishes a stacking context. It could
   // already be set in Widget::setStyle().
   if (widget->stackingContextMgr == NULL && IMPL_POS) {
      widget->stackingContextMgr = new StackingContextMgr (widget);
      DBG_OBJ_ASSOC (widget, widget->stackingContextMgr);
      widget->stackingContextWidget = widget;
   }
 
   topLevel = widget;
   widget->layout = this;
   widget->container = NULL;
   DBG_OBJ_SET_PTR_O (widget, "container", widget->container);
 
   queueResizeList->clear ();
   widget->notifySetAsTopLevel ();
 
   findtextState.setWidget (widget);
 
   canvasHeightGreater = false;
   DBG_OBJ_SET_SYM ("canvasHeightGreater",
                    canvasHeightGreater ? "true" : "false");
 
   // Do not directly call Layout::queueResize(), but
   // Widget::queueResize(), so that all flags are set properly,
   // queueResizeList is filled, etc.
   topLevel->queueResize (-1, false);
}
 
void Layout::removeWidget ()
{
   topLevel = NULL;
   queueResizeList->clear ();
   widgetAtPoint = NULL;
   canvasWidth = canvasAscent = canvasDescent = 0;
   scrollX = scrollY = 0;
 
   view->setCanvasSize (canvasWidth, canvasAscent, canvasDescent);
   if (view->usesViewport ())
      view->setViewportSize (viewportWidth, viewportHeight, 0, 0);
   view->queueDrawTotal ();
 
   setAnchor (NULL);
   updateAnchor ();
 
   emitter.emitCanvasSizeChanged (canvasWidth, canvasAscent, canvasDescent);
 
   findtextState.setWidget (NULL);
   selectionState.reset ();
 
   updateCursor ();
}
 
void Layout::setWidget (Widget *widget)
{
   DBG_OBJ_ASSOC_CHILD (widget);
 
   widgetAtPoint = NULL;
   if (topLevel) {
      Widget *w = topLevel;
      topLevel = NULL;
      delete w;
   }
   textZone->zoneFree ();
   addWidget (widget);
 
   updateCursor ();
 
   /* Reset the resizeCounter when we change the top level widget, as we are
    * changing to another page */
   resizeCounter = 0;
}
 
void Layout::attachView (View *view)
{
   if (this->view)
      MSG_ERR("attachView: Multiple views for layout!\n");
 
   DBG_OBJ_ASSOC_CHILD (view);
 
   this->view = view;
   platform->attachView (view);
 
   /*
    * The layout of the view is set later, first, we "project" the current
    * state of the layout into the new view. A view must handle this without
    * a layout. See also at the end of this function.
    */
   if (bgColor)
      view->setBgColor (bgColor);
   view->setCursor (cursor);
   view->setCanvasSize (canvasWidth, canvasAscent, canvasDescent);
 
   if (view->usesViewport ()) {
      if (usesViewport) {
         view->scrollTo (scrollX, scrollY);
         view->setViewportSize (viewportWidth, viewportHeight,
                                hScrollbarThickness, vScrollbarThickness);
         hScrollbarThickness = misc::max (hScrollbarThickness,
                                          view->getHScrollbarThickness ());
         vScrollbarThickness = misc::max (vScrollbarThickness,
                                          view->getVScrollbarThickness ());
      }
      else {
         usesViewport = true;
         scrollX = scrollY = 0;
         viewportWidth = viewportHeight = 100; // random values
         hScrollbarThickness = view->getHScrollbarThickness ();
         vScrollbarThickness = view->getVScrollbarThickness ();
      }
 
      DBG_OBJ_SET_NUM ("viewportWidth", viewportWidth);
      DBG_OBJ_SET_NUM ("viewportHeight", viewportHeight);
      DBG_OBJ_SET_NUM ("hScrollbarThickness", hScrollbarThickness);
      DBG_OBJ_SET_NUM ("vScrollbarThickness", vScrollbarThickness);
   }
 
   /*
    * This is the last call within this function, so that it is safe for
    * the implementation of dw::core::View::setLayout, to call methods
    * of dw::core::Layout.
    */
   view->setLayout (this);
}
 
void Layout::detachView (View *view)
{
   if (this->view != view) {
      MSG_ERR("detachView: this->view: %p view %p\n",
            (void *) this->view, (void *) view);
   }
 
   view->setLayout (NULL);
   platform->detachView (view);
   this->view = NULL;
}
 
void Layout::scroll(ScrollCommand cmd)
{
   if (view->usesViewport ())
      view->scroll(cmd);
}
 
void Layout::scrollTo (HPosition hpos, VPosition vpos,
                       int x, int y, int width, int height)
{
   scrollTo0 (hpos, vpos, x, y, width, height, true);
}
 
void Layout::scrollTo0 (HPosition hpos, VPosition vpos,
                        int x, int y, int width, int height,
                        bool scrollingInterrupted)
{
   if (usesViewport) {
      _MSG("scrollTo (%d, %d, %s)\n",
           x, y, scrollingInterrupted ? "true" : "false");
 
      scrollTargetHpos = hpos;
      scrollTargetVpos = vpos;
      scrollTargetX = x;
      scrollTargetY = y;
      scrollTargetWidth = width;
      scrollTargetHeight = height;
 
      if (scrollIdleId == -1) {
         scrollIdleId = platform->addIdle (&Layout::scrollIdle);
         scrollIdleNotInterrupted = true;
      }
 
      scrollIdleNotInterrupted =
         scrollIdleNotInterrupted || !scrollingInterrupted;
   }
}
 
void Layout::scrollIdle ()
{
   bool xChanged = true;
   switch (scrollTargetHpos) {
   case HPOS_LEFT:
      scrollX = scrollTargetX;
      break;
   case HPOS_CENTER:
      scrollX =
         scrollTargetX
         - (viewportWidth - currVScrollbarThickness() - scrollTargetWidth) / 2;
      break;
   case HPOS_RIGHT:
      scrollX =
         scrollTargetX
         - (viewportWidth - currVScrollbarThickness() - scrollTargetWidth);
      break;
   case HPOS_INTO_VIEW:
      xChanged = calcScrollInto (scrollTargetX, scrollTargetWidth, &scrollX,
                                 viewportWidth - currVScrollbarThickness());
      break;
   case HPOS_NO_CHANGE:
      xChanged = false;
      break;
   }
 
   bool yChanged = true;
   switch (scrollTargetVpos) {
   case VPOS_TOP:
      scrollY = scrollTargetY;
      break;
   case VPOS_CENTER:
      scrollY =
         scrollTargetY
         - (viewportHeight - currHScrollbarThickness() - scrollTargetHeight)/2;
      break;
   case VPOS_BOTTOM:
      scrollY =
         scrollTargetY
         - (viewportHeight - currHScrollbarThickness() - scrollTargetHeight);
      break;
   case VPOS_INTO_VIEW:
      yChanged = calcScrollInto (scrollTargetY, scrollTargetHeight, &scrollY,
                                 viewportHeight - currHScrollbarThickness());
      break;
   case VPOS_NO_CHANGE:
      yChanged = false;
      break;
   }
 
   if (xChanged || yChanged) {
      adjustScrollPos ();
      view->scrollTo (scrollX, scrollY);
      if (drawAfterScrollReq) {
         drawAfterScrollReq = false;
         view->queueDrawTotal ();
      }
   }
 
   scrollIdleId = -1;
}
 
void Layout::adjustScrollPos ()
{
   scrollX = misc::min (scrollX,
      canvasWidth - (viewportWidth - vScrollbarThickness));
   scrollX = misc::max (scrollX, 0);
 
   scrollY = misc::min (scrollY,
      canvasAscent + canvasDescent - (viewportHeight - hScrollbarThickness));
   scrollY = misc::max (scrollY, 0);
 
   _MSG("adjustScrollPos: scrollX=%d scrollY=%d\n", scrollX, scrollY);
}
 
bool Layout::calcScrollInto (int requestedValue, int requestedSize,
                             int *value, int viewportSize)
{
   if (requestedSize > viewportSize) {
      // The viewport size is smaller than the size of the region which will
      // be shown. If the region is already visible, do not change the
      // position. Otherwise, show the left/upper border, this is most likely
      // what is needed.
      if (*value >= requestedValue &&
          *value + viewportSize < requestedValue + requestedSize)
         return false;
      else
         requestedSize = viewportSize;
   }
 
   if (requestedValue < *value) {
      *value = requestedValue;
      return true;
   } else if (requestedValue + requestedSize > *value + viewportSize) {
      *value = requestedValue - viewportSize + requestedSize;
      return true;
   } else
      return false;
}
 
void Layout::draw (View *view, Rectangle *area)
{
   DBG_OBJ_ENTER ("draw", 0, "draw", "%d, %d, %d * %d",
                  area->x, area->y, area->width, area->height);
 
   Rectangle widgetArea, intersection, widgetDrawArea;
 
   // First of all, draw background image. (Unlike background *color*,
   // this is not a feature of the views.)
   if (bgImage != NULL && bgImage->getImgbufSrc() != NULL)
      style::drawBackgroundImage (view, bgImage, bgRepeat, bgAttachment,
                                  bgPositionX, bgPositionY,
                                  area->x, area->y, area->width,
                                  area->height, 0, 0,
                                  // Reference area: maximum of canvas size and
                                  // viewport size.
                                  misc::max (viewportWidth
                                             - (canvasHeightGreater ?
                                                vScrollbarThickness : 0),
                                             canvasWidth),
                                  misc::max (viewportHeight
                                             - hScrollbarThickness,
                                             canvasAscent + canvasDescent));
 
   if (scrollIdleId != -1) {
      /* scroll is pending, defer draw until after scrollIdle() */
      drawAfterScrollReq = true;
 
   } else if (topLevel) {
      /* Draw the top level widget. */
      widgetArea.x = topLevel->allocation.x;
      widgetArea.y = topLevel->allocation.y;
      widgetArea.width = topLevel->allocation.width;
      widgetArea.height = topLevel->getHeight ();
 
      if (area->intersectsWith (&widgetArea, &intersection)) {
         view->startDrawing (&intersection);
 
         /* Intersection in widget coordinates. */
         widgetDrawArea.x = intersection.x - topLevel->allocation.x;
         widgetDrawArea.y = intersection.y - topLevel->allocation.y;
         widgetDrawArea.width = intersection.width;
         widgetDrawArea.height = intersection.height;
 
         DrawingContext context (&widgetArea);
         topLevel->draw (view, &widgetDrawArea, &context);
 
         view->finishDrawing (&intersection);
      }
   }
 
   DBG_OBJ_LEAVE ();
}
 
int Layout::currHScrollbarThickness()
{
   return (canvasWidth > viewportWidth) ? hScrollbarThickness : 0;
}
 
int Layout::currVScrollbarThickness()
{
   return (canvasAscent + canvasDescent > viewportHeight) ?
          vScrollbarThickness : 0;
}
 
void Layout::setAnchor (const char *anchor)
{
   _MSG("setAnchor (%s)\n", anchor);
 
   if (requestedAnchor)
      free (requestedAnchor);
   requestedAnchor = anchor ? dStrdup (anchor) : NULL;
   updateAnchor ();
}
 
char *Layout::addAnchor (Widget *widget, const char* name)
{
   return addAnchor (widget, name, -1);
}
 
char *Layout::addAnchor (Widget *widget, const char* name, int y)
{
   String key (name);
   if (anchorsTable->contains (&key))
      return NULL;
   else {
      Anchor *anchor = new Anchor ();
      anchor->name = dStrdup (name);
      anchor->widget = widget;
      anchor->y = y;
 
      anchorsTable->put (new String (name), anchor);
      updateAnchor ();
 
      return anchor->name;
   }
}
 
void Layout::changeAnchor (Widget *widget, char* name, int y)
{
   String key (name);
   Anchor *anchor = anchorsTable->get (&key);
   assert (anchor);
   assert (anchor->widget == widget);
   anchor->y = y;
   updateAnchor ();
}
 
void Layout::removeAnchor (Widget *widget, char* name)
{
   String key (name);
   anchorsTable->remove (&key);
}
 
void Layout::updateAnchor ()
{
   Anchor *anchor;
   if (requestedAnchor) {
      String key (requestedAnchor);
      anchor = anchorsTable->get (&key);
   } else
      anchor = NULL;
 
   if (anchor == NULL) {
      if (scrollIdleId != -1 && !scrollIdleNotInterrupted) {
         platform->removeIdle (scrollIdleId);
         scrollIdleId = -1;
      }
   } else
      if (anchor->y != -1)
         scrollTo0 (HPOS_NO_CHANGE, VPOS_TOP, 0, anchor->y, 0, 0, false);
}
 
void Layout::setCursor (style::Cursor cursor)
{
   if (cursor != this->cursor) {
      this->cursor = cursor;
      view->setCursor (cursor);
   }
}
 
void Layout::updateCursor ()
{
   if (widgetAtPoint && widgetAtPoint->style)
      setCursor (widgetAtPoint->style->cursor);
   else
      setCursor (style::CURSOR_DEFAULT);
}
 
void Layout::setBgColor (style::Color *color)
{
   color->ref ();
 
   if (bgColor)
      bgColor->unref ();
 
   bgColor = color;
 
   if (view)
      view->setBgColor (bgColor);
}
 
void Layout::setBgImage (style::StyleImage *bgImage,
                         style::BackgroundRepeat bgRepeat,
                         style::BackgroundAttachment bgAttachment,
                         style::Length bgPositionX, style::Length bgPositionY)
{
   if (layoutImgRenderer && this->bgImage)
      this->bgImage->removeExternalImgRenderer (layoutImgRenderer);
 
   if (bgImage)
      bgImage->ref ();
 
   if (this->bgImage)
      this->bgImage->unref ();
 
   this->bgImage = bgImage;
   this->bgRepeat = bgRepeat;
   this->bgAttachment = bgAttachment;
   this->bgPositionX = bgPositionX;
   this->bgPositionY = bgPositionY;
 
   if (bgImage) {
      // Create instance of LayoutImgRenderer when needed. Until this
      // layout is deleted, "layoutImgRenderer" will be kept, since it
      // is not specific to the style, but only to this layout.
      if (layoutImgRenderer == NULL)
         layoutImgRenderer = new LayoutImgRenderer (this);
      bgImage->putExternalImgRenderer (layoutImgRenderer);
   }
}
 
 
void Layout::resizeIdle ()
{
   DBG_OBJ_ENTER0 ("resize", 0, "resizeIdle");
 
   enterResizeIdle ();
 
   // There are two commits, 2863:b749629fbfc9 and 4645:ab70f9ce4353, the second
   // reverting the former. Interrestingly, the second fixes a bug. However, it
   // should still examined what happens here, and what happens the other calls
   // to Layout::resizeIdle() which should be still in the queue. (See
   // Layout::queueResize(), where resizeIdleId is indeed checked.)
 
   for (int i = 0; resizeIdleId != -1; i++) {
 
      /* Prevent infinite resize loop, if we reach this point it is very likely
       * there is a bug in the layouting process */
      if (resizeLimit && resizeCounter >= 1000) {
         MSG_ERR("Emergency layout stop after %d iterations\n", resizeCounter);
         MSG_ERR("Please file a bug report with the complete console output\n");
         resizeIdleId = -1;
         break;
      }
 
      /* Only allow 100 iterations before returning to redraw the screen. */
      if (i >= 100) {
         MSG_WARN("Stopping layout loop after %d iterations\n", resizeCounter);
         break;
      }
 
      resizeCounter++;
 
      for (typed::Iterator <Widget> it = queueResizeList->iterator();
           it.hasNext (); ) {
         Widget *widget = it.getNext ();
 
         if (widget->resizeQueued ()) {
            widget->setFlags (Widget::NEEDS_RESIZE);
            widget->unsetFlags (Widget::RESIZE_QUEUED);
         }
 
         if (widget->allocateQueued ()) {
            widget->setFlags (Widget::NEEDS_ALLOCATE);
            widget->unsetFlags (Widget::ALLOCATE_QUEUED);
         }
 
         if (widget->extremesQueued ()) {
            widget->setFlags (Widget::EXTREMES_CHANGED);
            widget->unsetFlags (Widget::EXTREMES_QUEUED);
         }
      }
      queueResizeList->clear ();
 
      // Reset here, since below, queueResize() may be called again.
      resizeIdleId = -1;
 
      // If this method is triggered by a viewport change, we can save
      // time when the toplevel widget is not affected (as for a toplevel
      // image resource).
      if (topLevel &&
          (topLevel->needsResize () || topLevel->needsAllocate ())) {
         Requisition requisition;
         Allocation allocation;
 
         topLevel->sizeRequest (&requisition);
         DBG_OBJ_MSGF ("resize", 1, "toplevel size: %d * (%d + %d)",
                       requisition.width, requisition.ascent,
                       requisition.descent);
 
         // This method is triggered by Widget::queueResize, which will,
         // in any case, set NEEDS_ALLOCATE (indirectly, as ALLOCATE_QUEUED).
         // This assertion helps to find inconsistencies. (Cases where
         // this method is triggered by a viewport change, but the
         // toplevel widget is not affected, are filtered out some lines
         // above: "if (topLevel && topLevel->needsResize ())".)
         assert (topLevel->needsAllocate ());
 
         allocation.x = allocation.y = 0;
         if (usesViewport && view->getScrollbarOnLeft())
            allocation.x += currVScrollbarThickness();
         allocation.width = requisition.width;
         allocation.ascent = requisition.ascent;
         allocation.descent = requisition.descent;
         topLevel->sizeAllocate (&allocation);
 
         canvasWidth = requisition.width;
         canvasAscent = requisition.ascent;
         canvasDescent = requisition.descent;
         emitter.emitCanvasSizeChanged (canvasWidth, 
                                        canvasAscent, canvasDescent);
         // Tell the view about the new world size.
         view->setCanvasSize (canvasWidth, canvasAscent, canvasDescent);
 
         if (usesViewport) {
            int currHThickness = currHScrollbarThickness();
            int currVThickness = currVScrollbarThickness();
 
            if (!canvasHeightGreater &&
                canvasAscent + canvasDescent > viewportHeight - currHThickness) {
               canvasHeightGreater = true;
               DBG_OBJ_SET_SYM ("canvasHeightGreater",
                                canvasHeightGreater ? "true" : "false");
               containerSizeChanged ();
 
               // We need to place the top level widget at an offset, so
               // be sure that we allocate it with the new allocation.x
               if (view->getScrollbarOnLeft())
                  topLevel->setFlags(Widget::NEEDS_ALLOCATE);
            }
 
            // Set viewport sizes.
            view->setViewportSize (viewportWidth, viewportHeight,
                                   currHThickness, currVThickness);
         }
 
         // views are redrawn via Widget::resizeDrawImpl ()
      }
   }
   updateAnchor ();
 
   DBG_OBJ_MSGF ("resize", 1,
                 "after resizeIdle: resizeIdleId = %d", resizeIdleId);
   DBG_OBJ_LEAVE ();
 
   leaveResizeIdle ();
}
 
void Layout::queueDraw (int x, int y, int width, int height)
{
   Rectangle area;
   area.x = x;
   area.y = y;
   area.width = width;
   area.height = height;
 
   if (area.isEmpty ()) return;
 
   view->queueDraw (&area);
}
 
void Layout::queueDrawExcept (int x, int y, int width, int height,
   int ex, int ey, int ewidth, int eheight) {
 
   if (x == ex && y == ey && width == ewidth && height == eheight)
      return;
 
   // queueDraw() the four rectangles within rectangle (x, y, width, height)
   // around rectangle (ex, ey, ewidth, eheight).
   // Some or all of these may be empty.
 
   // upper left corner of the intersection rectangle
   int ix1 = misc::max (x, ex);
   int iy1 = misc::max (y, ey);
   // lower right corner of the intersection rectangle
   int ix2 = misc::min (x + width, ex + ewidth);
   int iy2 = misc::min (y + height, ey + eheight);
 
   queueDraw (x, y, width, iy1 - y);
   queueDraw (x, iy2, width, y + height - iy2);
   queueDraw (x, iy1, ix1 - x, iy2 - iy1);
   queueDraw (ix2, iy1, x + width - ix2, iy2 - iy1);
}
 
void Layout::queueResize (bool extremesChanged)
{
   DBG_OBJ_ENTER ("resize", 0, "queueResize", "%s",
                  extremesChanged ? "true" : "false");
 
   if (resizeIdleId == -1) {
      view->cancelQueueDraw ();
 
      resizeIdleId = platform->addIdle (&Layout::resizeIdle);
      DBG_OBJ_MSGF ("resize", 1, "setting resizeIdleId = %d", resizeIdleId);
   }
 
   emitter.emitResizeQueued (extremesChanged);
 
   DBG_OBJ_LEAVE ();
}
 
 
// Views
 
bool Layout::buttonEvent (ButtonEventType type, View *view, int numPressed,
                          int x, int y, ButtonState state, int button)
 
{
   EventButton event;
 
   moveToWidgetAtPoint (x, y, state);
 
   event.xCanvas = x;
   event.yCanvas = y;
   event.state = state;
   event.button = button;
   event.numPressed = numPressed;
 
   return processMouseEvent (&event, type);
}
 
bool Layout::motionNotify (View *view, int x, int y, ButtonState state)
{
   EventButton event;
 
   moveToWidgetAtPoint (x, y, state);
 
   event.xCanvas = x;
   event.yCanvas = y;
   event.state = state;
 
   return processMouseEvent (&event, MOTION_NOTIFY);
}
 
void Layout::enterNotify (View *view, int x, int y, ButtonState state)
{
   Widget *lastWidget;
   EventCrossing event;
 
   lastWidget = widgetAtPoint;
   moveToWidgetAtPoint (x, y, state);
 
   if (widgetAtPoint) {
      event.state = state;
      event.lastWidget = lastWidget;
      event.currentWidget = widgetAtPoint;
      widgetAtPoint->enterNotify (&event);
   }
}
 
void Layout::leaveNotify (View *view, ButtonState state)
{
#if 0
   Widget *lastWidget;
   EventCrossing event;
 
   lastWidget = widgetAtPoint;
   moveOutOfView (state);
 
   if (lastWidget) {
      event.state = state;
      event.lastWidget = lastWidget;
      event.currentWidget = widgetAtPoint;
      lastWidget->leaveNotify (&event);
   }
#else
   moveOutOfView (state);
#endif
}
 
/*
 * Return the widget at position (x, y). Return NULL, if there is no widget.
 */
Widget *Layout::getWidgetAtPoint (int x, int y)
{
   DBG_OBJ_ENTER ("events", 0, "getWidgetAtPoint", "%d, %d", x, y);
   Widget *widget;
 
   if (topLevel && topLevel->wasAllocated ()) {
      GettingWidgetAtPointContext context;
      widget = topLevel->getWidgetAtPoint (x, y, &context);
   } else
      widget = NULL;
 
   DBG_OBJ_MSGF ("events", 0, "=> %p", widget);
   DBG_OBJ_LEAVE ();
   return widget;
}
 
 
/*
 * Emit the necessary crossing events, when the mouse pointer has moved to
 * the given widget (by mouse or scrolling).
 */
void Layout::moveToWidget (Widget *newWidgetAtPoint, ButtonState state)
{
   DBG_OBJ_ENTER ("events", 0, "moveToWidget", "%p, %d",
                  newWidgetAtPoint, state);
 
   Widget *ancestor, *w;
   Widget **track;
   int trackLen, i, i_a;
   EventCrossing crossingEvent;
 
   DBG_OBJ_MSGF ("events", 1, "(old) widgetAtPoint = %p", widgetAtPoint);
 
   if (newWidgetAtPoint != widgetAtPoint) {
      // The mouse pointer has been moved into another widget.
      if (newWidgetAtPoint && widgetAtPoint)
         ancestor =
            newWidgetAtPoint->getNearestCommonAncestor (widgetAtPoint);
      else if (newWidgetAtPoint)
         ancestor = newWidgetAtPoint->getTopLevel ();
      else
         ancestor = widgetAtPoint->getTopLevel ();
 
      // Construct the track.
      trackLen = 0;
      if (widgetAtPoint)
         // first part
         for (w = widgetAtPoint; w != ancestor; w = w->getParent ())
            trackLen++;
      trackLen++; // for the ancestor
      if (newWidgetAtPoint)
         // second part
         for (w = newWidgetAtPoint; w != ancestor; w = w->getParent ())
            trackLen++;
 
      track = new Widget* [trackLen];
      i = 0;
      if (widgetAtPoint)
         /* first part */
         for (w = widgetAtPoint; w != ancestor; w = w->getParent ())
            track[i++] = w;
      i_a = i;
      track[i++] = ancestor;
      if (newWidgetAtPoint) {
         /* second part */
         i = trackLen - 1;
         for (w = newWidgetAtPoint; w != ancestor; w = w->getParent ())
            track[i--] = w;
      }
#if 0
      MSG("Track: %s[ ", widgetAtPoint ? "" : "nil ");
      for (i = 0; i < trackLen; i++)
         MSG("%s%p ", i == i_a ? ">" : "", track[i]);
      MSG("] %s\n", newWidgetAtPoint ? "" : "nil");
#endif
 
      /* Send events to the widgets on the track */
      for (i = 0; i < trackLen; i++) {
         crossingEvent.state = state;
         crossingEvent.currentWidget = widgetAtPoint; // ???
         crossingEvent.lastWidget = widgetAtPoint; // ???
         if (i < i_a) {
            track[i]->leaveNotify (&crossingEvent);
         } else if (i == i_a) { /* ancestor */
            /* Don't touch ancestor unless:
             *   - moving into/from NULL,
             *   - ancestor becomes the newWidgetAtPoint */
            if (i_a == trackLen-1 && !newWidgetAtPoint)
               track[i]->leaveNotify (&crossingEvent);
            else if ((i_a == 0 && !widgetAtPoint) ||
                     (i_a == trackLen-1 && newWidgetAtPoint))
               track[i]->enterNotify (&crossingEvent);
         } else {
            track[i]->enterNotify (&crossingEvent);
         }
      }
 
      delete[] track;
 
      widgetAtPoint = newWidgetAtPoint;
      updateCursor ();
   }
 
   DBG_OBJ_LEAVE ();
}
 
bool Layout::processMouseEvent (MousePositionEvent *event,
                                ButtonEventType type)
{
   Widget *widget;
 
   /*
    * If the event is outside of the visible region of the canvas, treat it
    * as occurring at the region's edge. Notably, this helps when selecting
    * text.
    */
   if (event->xCanvas < scrollX)
      event->xCanvas = scrollX;
   else {
      int maxX = scrollX + viewportWidth - currVScrollbarThickness() - 1;
 
      if (event->xCanvas > maxX)
         event->xCanvas = maxX;
   }
   if (event->yCanvas < scrollY)
      event->yCanvas = scrollY;
   else {
      int maxY = misc::min(scrollY + viewportHeight -currHScrollbarThickness(),
                           canvasAscent + canvasDescent) - 1;
 
      if (event->yCanvas > maxY)
         event->yCanvas = maxY;
   }
 
   widget = getWidgetAtPoint(event->xCanvas, event->yCanvas);
 
   for (; widget; widget = widget->getParent ()) {
      if (widget->isButtonSensitive ()) {
         event->xWidget = event->xCanvas - widget->getAllocation()->x;
         event->yWidget = event->yCanvas - widget->getAllocation()->y;
 
         switch (type) {
         case BUTTON_PRESS:
            return widget->buttonPress ((EventButton*)event);
 
         case BUTTON_RELEASE:
            return widget->buttonRelease ((EventButton*)event);
 
         case MOTION_NOTIFY:
            return widget->motionNotify ((EventMotion*)event);
 
         default:
            misc::assertNotReached ();
         }
      }
   }
   if (type == BUTTON_PRESS)
      return emitLinkPress (NULL, -1, -1, -1, -1, (EventButton*)event);
   else if (type == BUTTON_RELEASE)
      return emitLinkRelease(NULL, -1, -1, -1, -1, (EventButton*)event);
 
   return false;
}
 
/*
 * This function must be called by a view, when the user has manually changed
 * the viewport position. It is *not* called, when the layout has requested the
 * position change.
 */
void Layout::scrollPosChanged (View *view, int x, int y)
{
   if (x != scrollX || y != scrollY) {
      scrollX = x;
      scrollY = y;
 
      setAnchor (NULL);
      updateAnchor ();
   }
}
 
/*
 * This function must be called by a viewport view, when its viewport size has
 * changed. It is *not* called, when the layout has requested the size change.
 */
void Layout::viewportSizeChanged (View *view, int width, int height)
{
   DBG_OBJ_ENTER ("resize", 0, "viewportSizeChanged", "%p, %d, %d",
                 view, width, height);
 
   /* If size changes, redraw this view. */
   if (viewportWidth != width || viewportHeight != height) {
      canvasHeightGreater = false;   // reset value here
      viewportWidth = width;
      viewportHeight = height;
      resizeCounter = 0;
      containerSizeChanged ();
 
      DBG_OBJ_SET_SYM ("canvasHeightGreater",
                       canvasHeightGreater ? "true" : "false");
      DBG_OBJ_SET_NUM ("viewportWidth", viewportWidth);
      DBG_OBJ_SET_NUM ("viewportHeight", viewportHeight);
   }
 
   DBG_OBJ_LEAVE ();
}
 
void Layout::containerSizeChanged ()
{
   DBG_OBJ_ENTER0 ("resize", 0, "containerSizeChanged");
 
   if (topLevel) {
      topLevel->containerSizeChanged ();
      queueResize (true);
   }
 
   DBG_OBJ_LEAVE ();
}
 
} // namespace core
} // namespace dw