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/*
* $Id$
* Copyright (C) 2001 The Apache Software Foundation. All rights reserved.
* For details on use and redistribution please refer to the
* LICENSE file included with these sources.
*/
package org.apache.fop.layoutmgr;
import org.apache.fop.fo.FObj;
import org.apache.fop.area.Area;
import org.apache.fop.area.BlockParent;
import org.apache.fop.area.Block;
import org.apache.fop.area.MinOptMax;
import java.util.Iterator;
/**
* Base LayoutManager class for all areas which stack their child
* areas in the block-progression direction, such as Flow, Block, ListBlock.
*/
public abstract class BlockStackingLayoutManager extends AbstractLayoutManager {
/** Reference to FO whose areas it's managing or to the traits
* of the FO.
*/
LayoutManager curChildLM = null;
BlockParent parentArea = null;
public BlockStackingLayoutManager(FObj fobj) {
super(fobj);
}
public boolean splitArea(Area area, SplitContext splitContext) {
// Divide area so that it will be within targetLength if possible
// If not, it can be shorter, but not longer.
/* Iterate over contents of the area. */
// Need to figure out if we can do this generically
// Logically a BlockStacking LM only handles Block-type areas
if (!(area instanceof BlockParent)) {
return false;
}
Iterator areaIter = ((BlockParent) area).getChildAreas().iterator();
BreakCost minBreakCost = null;
MinOptMax remainBPD = splitContext.targetBPD;
splitContext.nextArea = area;
while (areaIter.hasNext()) {
Area childArea = (Area) areaIter.next();
if (remainBPD.max < childArea.getAllocationBPD().min) {
// Past the end point: try to break it
// TODO: get a LayoutManager to do the split of the child
// area, either Area => LM or Area => gen FO => LM
LayoutManager childLM =
childArea.getGeneratingFObj(). getLayoutManager();
splitContext.targetBPD = remainBPD;
if (childLM.splitArea(childArea, splitContext) == false) {
// Can't split, so must split this area before childArea
// Can we pass the iter?
// If already saw several a potential break, use it
if (minBreakCost != null) {
/* Split 'area', placing all children after
* minBreakCost.getArea() into a new area,
* which we store in the splitContext.
*/
// splitContext.nextArea = area.splitAfter(minBreakCost.getArea());
} else {
/* This area will be shorter than the desired minimum.
* Split before the current childArea (which will be
* the first area in the newly created Area.
*/
//splitContext.nextArea = area.splitBefore(childArea);
}
} else
return true; // childLM has done the work for us!
// Set cost, dimension ???
break;
} else {
remainBPD.subtract(childArea.getAllocationBPD());
if (remainBPD.min < 0) {
// Potential breakpoint: remember break Position and
// break "cost" (constraint violation)
BreakCost breakCost =
evaluateBreakCost(area, childArea);
minBreakCost = breakCost.chooseLowest(minBreakCost);
}
}
//Note: size of area when split can depend on conditional
// space, border and padding of the split area!!!
}
// True if some part of area can be placed, false if none is placed
return (splitContext.nextArea != area);
}
private BreakCost evaluateBreakCost(Area parent, Area child) {
return new BreakCost(child, 0);
}
/** return current area being filled
*/
protected BlockParent getCurrentArea() {
return this.parentArea;
}
/**
* Set the current area being filled.
*/
protected void setCurrentArea(BlockParent parentArea) {
this.parentArea = parentArea;
}
protected MinOptMax resolveSpaceSpecifier(Area nextArea) {
SpaceSpecifier spaceSpec = new SpaceSpecifier();
// Area prevArea = getCurrentArea().getLast();
// if (prevArea != null) {
// spaceSpec.addSpace(prevArea.getSpaceAfter());
// }
// spaceSpec.addSpace(nextArea.getSpaceBefore());
return spaceSpec.resolve();
}
/**
* Add the childArea to the passed area.
* Called by child LayoutManager when it has filled one of its areas.
* The LM should already have an Area in which to put the child.
* See if the area will fit in the current area.
* If so, add it. Otherwise initiate breaking.
* @param childArea the area to add: will be some block-stacked Area.
* @param parentArea the area in which to add the childArea
*/
protected void addChildToArea(Area childArea, BlockParent parentArea) {
// This should be a block-level Area (Block in the generic sense)
if (!(childArea instanceof Block)) {
System.err.println("Child not a Block in BlockStackingLM!");
return;
}
// See if the whole thing fits, including space before
// Calculate space between last child in curFlow and childArea
MinOptMax targetDim = parentArea.getAvailBPD();
MinOptMax spaceBefore = resolveSpaceSpecifier(childArea);
targetDim.subtract(spaceBefore);
if (targetDim.max >= childArea.getAllocationBPD().min) {
//parentArea.addBlock(new InterBlockSpace(spaceBefore));
parentArea.addBlock((Block) childArea);
return;
} else {
// Probably need something like max BPD so we don't get into
// infinite loops with large unbreakable chunks
SplitContext splitContext = new SplitContext(targetDim);
LayoutManager childLM =
childArea.getGeneratingFObj(). getLayoutManager();
if (childLM.splitArea(childArea, splitContext)) {
//parentArea.addBlock(new InterBlockSpace(spaceBefore));
parentArea.addBlock((Block) childArea);
}
flush(); // hand off current area to parent
getParentArea(splitContext.nextArea);
// Check that reference IPD hasn't changed!!!
// If it has, we must "reflow" the content
addChild(splitContext.nextArea);
}
}
/**
* Add the childArea to the current area.
* Called by child LayoutManager when it has filled one of its areas.
* The LM should already have an Area in which to put the child.
* See if the area will fit in the current area.
* If so, add it. Otherwise initiate breaking.
* @param childArea the area to add: will be some block-stacked Area.
*/
public void addChild(Area childArea) {
addChildToArea(childArea, getCurrentArea());
}
/**
* Force current area to be added to parent area.
*/
protected void flush() {
if (getCurrentArea() != null)
parentLM.addChild(getCurrentArea());
}
}
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