netsurf/render/layout.c

/*
 * This file is part of NetSurf, http://netsurf.sourceforge.net/
 * Licensed under the GNU General Public License,
 *                http://www.opensource.org/licenses/gpl-license
 * Copyright 2004 James Bursa <bursa@users.sourceforge.net>
 * Copyright 2003 Phil Mellor <monkeyson@users.sourceforge.net>
 */

/** \file
 * HTML layout (implementation).
 *
 * Layout is carried out in a single pass through the box tree, except for
 * precalculation of minimum / maximum box widths.
 */

#include <alloca.h>
#include <assert.h>
#include <ctype.h>
#include <limits.h>
#include <stdbool.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include "netsurf/css/css.h"
#include "netsurf/content/content.h"
#ifdef riscos
#include "netsurf/desktop/gui.h"
#endif
#include "netsurf/desktop/options.h"
#include "netsurf/render/box.h"
#include "netsurf/render/font.h"
#include "netsurf/render/layout.h"
#define NDEBUG
#include "netsurf/utils/log.h"
#include "netsurf/utils/pool.h"
#include "netsurf/utils/utils.h"


#define AUTO INT_MIN


static void layout_block_find_dimensions(int available_width, struct box *box);
static int layout_solve_width(int available_width, int width,
		int margin[4], int padding[4], int border[4]);
static void layout_float_find_dimensions(int available_width,
		struct css_style *style, struct box *box);
static void layout_find_dimensions(int available_width,
		struct css_style *style,
		int margin[4], int padding[4], int border[4]);
static int layout_clear(struct box *fl, css_clear clear);
static void find_sides(struct box *fl, int y0, int y1,
		int *x0, int *x1, struct box **left, struct box **right);
static int line_height(struct css_style *style);
static bool layout_line(struct box *first, int width, int *y,
		int cx, int cy, struct box *cont, bool indent,
		pool box_pool, struct box **next_box);
static int layout_text_indent(struct css_style *style, int width);
static bool layout_float(struct box *b, int width, pool box_pool);
static void place_float_below(struct box *c, int width, int cx, int y,
		struct box *cont);
static bool layout_table(struct box *box, int available_width, pool box_pool);
static bool calculate_widths(struct box *box);
static bool calculate_block_widths(struct box *box, int *min, int *max,
		int *max_sum);
static bool calculate_inline_container_widths(struct box *box);
static void calculate_inline_replaced_widths(struct box *box, int *min,
		int *max, int *line_max);
static void calculate_inline_widths(struct box *box, int *min, int *line_max);
static bool calculate_table_widths(struct box *table);
static void layout_calculate_descendant_bboxes(struct box *box);


/**
 * Calculate positions of boxes in a document.
 *
 * \param  doc       root of document box tree
 * \param  width     available page width
 * \param  box_pool  memory pool for any new boxes
 * \return  true on success, false on memory exhaustion
 */

bool layout_document(struct box *doc, int width, pool box_pool)
{
	bool ret;

	doc->float_children = 0;

	if (!calculate_widths(doc))
		return false;

	layout_block_find_dimensions(width, doc);
	doc->x = doc->margin[LEFT] + doc->border[LEFT];
	doc->y = doc->margin[TOP] + doc->border[TOP];
	width -= doc->margin[LEFT] + doc->border[LEFT] +
			doc->border[RIGHT] + doc->margin[RIGHT];
	doc->width = width;

	ret = layout_block_context(doc, box_pool);

	layout_calculate_descendant_bboxes(doc);

	return ret;
}


/**
 * Layout a block formatting context.
 *
 * \param  block  BLOCK, INLINE_BLOCK, or TABLE_CELL to layout.
 * \param  box_pool  memory pool for any new boxes
 * \return  true on success, false on memory exhaustion
 *
 * This function carries out layout of a block and its children, as described
 * in CSS 2.1 9.4.1.
 */

bool layout_block_context(struct box *block, pool box_pool)
{
	struct box *box;
	int cx;
	int cy;
	int max_pos_margin = 0;
	int max_neg_margin = 0;
	int y;
	struct box *margin_box;

	assert(block->type == BOX_BLOCK ||
			block->type == BOX_INLINE_BLOCK ||
			block->type == BOX_TABLE_CELL);

	gui_multitask();

	box = margin_box = block->children;
	cx = block->padding[LEFT];
	cy = block->padding[TOP];
	if (box)
		box->y = block->padding[TOP];

	while (box) {
		assert(box->type == BOX_BLOCK || box->type == BOX_TABLE ||
				box->type == BOX_INLINE_CONTAINER);
		assert(margin_box);

		/* Tables are laid out before being positioned, because the
		 * position depends on the width which is calculated in
		 * table layout. Blocks and inline containers are positioned
		 * before being laid out, because width is not dependent on
		 * content, and the position is required during layout for
		 * correct handling of floats.
		 */

		if (box->type == BOX_BLOCK)
			layout_block_find_dimensions(box->parent->width, box);
		else if (box->type == BOX_TABLE) {
			if (!layout_table(box, box->parent->width, box_pool))
				return false;
			layout_solve_width(box->parent->width, box->width,
					box->margin, box->padding, box->border);
		}

		/* Position box: horizontal. */
		box->x = box->parent->padding[LEFT] + box->margin[LEFT] +
				box->border[LEFT];
		cx += box->x;

		/* Position box: top margin. */
		if (max_pos_margin < box->margin[TOP])
			max_pos_margin = box->margin[TOP];
		else if (max_neg_margin < -box->margin[TOP])
			max_neg_margin = -box->margin[TOP];

		/* Clearance. */
		y = 0;
		if (box->style && box->style->clear != CSS_CLEAR_NONE)
			y = layout_clear(block->float_children,
					box->style->clear);

		if (box->type != BOX_BLOCK || y ||
				box->border[TOP] || box->padding[TOP]) {
			margin_box->y += max_pos_margin - max_neg_margin;
			cy += max_pos_margin - max_neg_margin;
			max_pos_margin = max_neg_margin = 0;
			margin_box = 0;
			box->y += box->border[TOP];
			cy += box->border[TOP];
			if (cy < y) {
				box->y += y - cy;
				cy = y;
			}
		}

		/* Layout (except tables). */
		if (box->type == BOX_INLINE_CONTAINER) {
			box->width = box->parent->width;
			if (!layout_inline_container(box, box->width, block,
					cx, cy, box_pool))
				return false;
		} else if (box->type == BOX_TABLE) {
			/* Move down to avoid floats if necessary. */
			int x0, x1;
			struct box *left, *right;
			y = cy;
			while (1) {
				x0 = cx;
				x1 = cx + box->parent->width;
				find_sides(block->float_children, y,
						y + box->height,
						&x0, &x1, &left, &right);
				if (box->width <= x1 - x0)
					break;
				if (!left && !right)
					break;
				else if (!left)
					y = right->y + right->height + 1;
				else if (!right)
					y = left->y + left->height + 1;
				else if (left->y + left->height <
						right->y + right->height)
					y = left->y + left->height + 1;
				else
					y = right->y + right->height + 1;
			}
			box->x += x0 - cx;
			cx = x0;
			box->y += y - cy;
			cy = y;
		}

		/* Advance to next box. */
		if (box->type == BOX_BLOCK && box->children) {
			y = box->padding[TOP];
			box = box->children;
			box->y = y;
			cy += y;
			if (!margin_box) {
				max_pos_margin = max_neg_margin = 0;
				margin_box = box;
			}

			continue;
		}
		if (box->type == BOX_BLOCK && box->height == AUTO)
			box->height = 0;
		cy += box->height + box->padding[BOTTOM] + box->border[BOTTOM];
		max_pos_margin = max_neg_margin = 0;
		if (max_pos_margin < box->margin[BOTTOM])
			max_pos_margin = box->margin[BOTTOM];
		else if (max_neg_margin < -box->margin[BOTTOM])
			max_neg_margin = -box->margin[BOTTOM];
		if (!box->next) {
			do {
				cx -= box->x;
				y = box->y + box->padding[TOP] + box->height +
						box->padding[BOTTOM] +
						box->border[BOTTOM];
				box = box->parent;
				if (box != block && box->height == AUTO)
					box->height = y - box->padding[TOP];
				cy += box->padding[BOTTOM] +
						box->border[BOTTOM];
				if (max_pos_margin < box->margin[BOTTOM])
					max_pos_margin = box->margin[BOTTOM];
				else if (max_neg_margin < -box->margin[BOTTOM])
					max_neg_margin = -box->margin[BOTTOM];
			} while (box != block && !box->next);
			if (box == block)
				break;
		}
		cx -= box->x;
		y = box->y + box->padding[TOP] + box->height +
				box->padding[BOTTOM] + box->border[BOTTOM];
		box = box->next;
		box->y = y;
		margin_box = box;
	}

	/* Increase height to contain any floats inside (CSS 2.1 10.6.7). */
	for (box = block->float_children; box; box = box->next_float) {
		y = box->y + box->height + box->padding[BOTTOM] +
				box->border[BOTTOM] + box->margin[BOTTOM];
		if (cy < y)
			cy = y;
	}

	if (block->height == AUTO)
		block->height = cy - block->padding[TOP];

	return true;
}


/**
 * Compute dimensions of box, margins, paddings, and borders for a block-level
 * element.
 *
 * See CSS 2.1 10.3.3, 10.3.4, 10.6.2, and 10.6.3.
 */

void layout_block_find_dimensions(int available_width, struct box *box)
{
	int width;
	int *margin = box->margin;
	int *padding = box->padding;
	int *border = box->border;
	struct css_style *style = box->style;

	/* calculate box width */
	switch (style->width.width) {
		case CSS_WIDTH_LENGTH:
			width = len(&style->width.value.length, style);
			break;
		case CSS_WIDTH_PERCENT:
			width = available_width * style->width.value.percent / 100;
			break;
		case CSS_WIDTH_AUTO:
		default:
			width = AUTO;
			break;
	}

	/* height */
	switch (style->height.height) {
		case CSS_HEIGHT_LENGTH:
			box->height = len(&style->height.length, style);
			break;
		case CSS_HEIGHT_AUTO:
		default:
			box->height = AUTO;
			break;
	}

	if (box->object) {
		/* block-level replaced element, see 10.3.4 and 10.6.2 */
		if (width == AUTO && box->height == AUTO) {
			width = box->object->width;
			box->height = box->object->height;
		} else if (width == AUTO) {
			if (box->object->height)
				width = box->object->width *
						(float) box->height /
						box->object->height;
			else
				width = box->object->width;
		} else if (box->height == AUTO) {
			if (box->object->width)
				box->height = box->object->height *
						(float) width /
						box->object->width;
			else
				box->height = box->object->height;
		}
	}

	layout_find_dimensions(available_width, style, margin, padding, border);

	box->width = layout_solve_width(available_width, width, margin,
			padding, border);

	if (box->object && box->object->type == CONTENT_HTML &&
			 box->width != box->object->available_width) {
		content_reformat(box->object, box->width, box->height);
		if (style->height.height == CSS_HEIGHT_AUTO)
			box->height = box->object->height;
	}

	if (margin[TOP] == AUTO)
		margin[TOP] = 0;
	if (margin[BOTTOM] == AUTO)
		margin[BOTTOM] = 0;
}


/**
 * Solve the width constraint as given in CSS 2.1 section 10.3.3.
 */

int layout_solve_width(int available_width, int width,
		int margin[4], int padding[4], int border[4])
{
	if (width == AUTO) {
		/* any other 'auto' become 0 */
		if (margin[LEFT] == AUTO)
			margin[LEFT] = 0;
		if (margin[RIGHT] == AUTO)
			margin[RIGHT] = 0;
		width = available_width -
				(margin[LEFT] + border[LEFT] + padding[LEFT] +
				 padding[RIGHT] + border[RIGHT] + margin[RIGHT]);
	} else if (margin[LEFT] == AUTO && margin[RIGHT] == AUTO) {
		/* make the margins equal, centering the element */
		margin[LEFT] = margin[RIGHT] = (available_width -
				(border[LEFT] + padding[LEFT] + width +
				 padding[RIGHT] + border[RIGHT])) / 2;
		if (margin[LEFT] < 0) {
			margin[RIGHT] += margin[LEFT];
			margin[LEFT] = 0;
		}
	} else if (margin[LEFT] == AUTO) {
		margin[LEFT] = available_width -
				(border[LEFT] + padding[LEFT] + width +
				 padding[RIGHT] + border[RIGHT] + margin[RIGHT]);
	} else {
		/* margin-right auto or "over-constained" */
		margin[RIGHT] = available_width -
				(margin[LEFT] + border[LEFT] + padding[LEFT] +
				 width + padding[RIGHT] + border[RIGHT]);
	}

	return width;
}


/**
 * Compute dimensions of box, margins, paddings, and borders for a floating
 * element.
 */

void layout_float_find_dimensions(int available_width,
		struct css_style *style, struct box *box)
{
	layout_find_dimensions(available_width, style,
			box->margin, box->padding, box->border);

	if (box->margin[LEFT] == AUTO)
		box->margin[LEFT] = 0;
	if (box->margin[RIGHT] == AUTO)
		box->margin[RIGHT] = 0;

	/* calculate box width */
	switch (style->width.width) {
		case CSS_WIDTH_LENGTH:
			box->width = len(&style->width.value.length, style);
			break;
		case CSS_WIDTH_PERCENT:
			box->width = available_width *
					style->width.value.percent / 100;
			break;
		case CSS_WIDTH_AUTO:
		default:
			box->width = AUTO;
			break;
	}

	/* height */
	switch (style->height.height) {
		case CSS_HEIGHT_LENGTH:
			box->height = len(&style->height.length, style);
			break;
		case CSS_HEIGHT_AUTO:
		default:
			box->height = AUTO;
			break;
	}

	if (box->object) {
		/* floating replaced element, see 10.3.6 and 10.6.2 */
		if (box->width == AUTO && box->height == AUTO) {
			box->width = box->object->width;
			box->height = box->object->height;
		} else if (box->width == AUTO)
			box->width = box->object->width * (float) box->height /
					box->object->height;
		else if (box->height == AUTO)
			box->height = box->object->height * (float) box->width /
					box->object->width;
	} else if (box->width == AUTO) {
		/* CSS 2.1 section 10.3.5 */
		available_width -= box->margin[LEFT] + box->border[LEFT] +
				box->padding[LEFT] + box->padding[RIGHT] +
				box->border[RIGHT] + box->margin[RIGHT];
		if (box->min_width < available_width)
			box->width = available_width;
		else
			box->width = box->min_width;
		if (box->max_width < box->width)
			box->width = box->max_width;
	}

	if (box->margin[TOP] == AUTO)
		box->margin[TOP] = 0;
	if (box->margin[BOTTOM] == AUTO)
		box->margin[BOTTOM] = 0;
}


/**
 * Calculate size of margins, paddings, and borders.
 */

void layout_find_dimensions(int available_width,
		struct css_style *style,
		int margin[4], int padding[4], int border[4])
{
	unsigned int i;
	for (i = 0; i != 4; i++) {
		switch (style->margin[i].margin) {
			case CSS_MARGIN_LENGTH:
				margin[i] = len(&style->margin[i].value.length, style);
				break;
			case CSS_MARGIN_PERCENT:
				margin[i] = available_width *
						style->margin[i].value.percent / 100;
				break;
			case CSS_MARGIN_AUTO:
			default:
				margin[i] = AUTO;
				break;
		}

		switch (style->padding[i].padding) {
			case CSS_PADDING_PERCENT:
				padding[i] = available_width *
						style->padding[i].value.percent / 100;
				break;
			case CSS_PADDING_LENGTH:
			default:
				padding[i] = len(&style->padding[i].value.length, style);
				break;
		}

		if (style->border[i].style == CSS_BORDER_STYLE_NONE ||
				style->border[i].style == CSS_BORDER_STYLE_HIDDEN)
			/* spec unclear: following Mozilla */
			border[i] = 0;
		else
			border[i] = len(&style->border[i].width.value, style);
	}
}


/**
 * Find y coordinate which clears all floats on left and/or right.
 *
 * \param  fl     first float in float list
 * \param  clear  type of clear
 * \return  y coordinate relative to ancestor box for floats
 */

int layout_clear(struct box *fl, css_clear clear)
{
	int y = 0;
	for (; fl; fl = fl->next_float) {
		if ((clear == CSS_CLEAR_LEFT || clear == CSS_CLEAR_BOTH) &&
				fl->type == BOX_FLOAT_LEFT)
			if (y < fl->y + fl->height + 1)
				y = fl->y + fl->height + 1;
		if ((clear == CSS_CLEAR_RIGHT || clear == CSS_CLEAR_BOTH) &&
				fl->type == BOX_FLOAT_RIGHT)
			if (y < fl->y + fl->height + 1)
				y = fl->y + fl->height + 1;
	}
	return y;
}


/**
 * Find left and right edges in a vertical range.
 *
 * \param  fl     first float in float list
 * \param  y0     start of y range to search
 * \param  y1     end of y range to search
 * \param  x0     start left edge, updated to available left edge
 * \param  x1     start right edge, updated to available right edge
 * \param  left   returns float on left if present
 * \param  right  returns float on right if present
 */

void find_sides(struct box *fl, int y0, int y1,
		int *x0, int *x1, struct box **left, struct box **right)
{
	int fy0, fy1, fx0, fx1;
	LOG(("y0 %i, y1 %i, x0 %i, x1 %i", y0, y1, *x0, *x1));
	*left = *right = 0;
	for (; fl; fl = fl->next_float) {
		fy0 = fl->y;
		fy1 = fl->y + fl->height;
		if (y0 <= fy1 && fy0 <= y1) {
			if (fl->type == BOX_FLOAT_LEFT) {
				fx1 = fl->x + fl->width;
				if (*x0 < fx1) {
					*x0 = fx1;
					*left = fl;
				}
			} else if (fl->type == BOX_FLOAT_RIGHT) {
				fx0 = fl->x;
				if (fx0 < *x1) {
					*x1 = fx0;
					*right = fl;
				}
			}
		}
	}
	LOG(("x0 %i, x1 %i, left %p, right %p", *x0, *x1, *left, *right));
}


/**
 * Layout lines of text or inline boxes with floats.
 *
 * \param  box    inline container
 * \param  width  horizontal space available
 * \param  cont   ancestor box which defines horizontal space, for floats
 * \param  cx     box position relative to cont
 * \param  cy     box position relative to cont
 * \param  box_pool  memory pool for any new boxes
 * \return  true on success, false on memory exhaustion
 */

bool layout_inline_container(struct box *box, int width,
		struct box *cont, int cx, int cy, pool box_pool)
{
	bool first_line = true;
	struct box *c, *next;
	int y = 0;

	assert(box->type == BOX_INLINE_CONTAINER);

	LOG(("box %p, width %i, cont %p, cx %i, cy %i",
			box, width, cont, cx, cy));

	for (c = box->children; c; ) {
		LOG(("c %p", c));
		if (!layout_line(c, width, &y, cx, cy + y, cont, first_line,
				box_pool, &next))
			return false;
		c = next;
		first_line = false;
	}

	box->width = width;
	box->height = y;

	return true;
}


/**
 * Calculate line height from a style.
 */

int line_height(struct css_style *style)
{
	float font_len;

	assert(style);
	assert(style->line_height.size == CSS_LINE_HEIGHT_LENGTH ||
	       style->line_height.size == CSS_LINE_HEIGHT_ABSOLUTE ||
	       style->line_height.size == CSS_LINE_HEIGHT_PERCENT);

	/* take account of minimum font size option */
	if ((font_len = len(&style->font_size.value.length, 0)) <
	    ((float)(option_font_min_size * 9.0 / 72.0)))
		font_len = (float)(option_font_min_size * 9.0 / 72.0);

	switch (style->line_height.size) {
		case CSS_LINE_HEIGHT_LENGTH:
			return len(&style->line_height.value.length, style);

		case CSS_LINE_HEIGHT_ABSOLUTE:
			return style->line_height.value.absolute * font_len;

		case CSS_LINE_HEIGHT_PERCENT:
		default:
			return style->line_height.value.percent * font_len
					/ 100.0;
	}
}


/**
 * Position a line of boxes in inline formatting context.
 *
 * \param  first   box at start of line
 * \param  width   available width
 * \param  y       coordinate of top of line, updated on exit to bottom
 * \param  cx      coordinate of left of line relative to cont
 * \param  cy      coordinate of top of line relative to cont
 * \param  cont    ancestor box which defines horizontal space, for floats
 * \param  indent  apply any first-line indent
 * \param  next_box  updated to first box for next line, or 0 at end
 * \param  box_pool  memory pool for any new boxes
 * \return  true on success, false on memory exhaustion
 */

bool layout_line(struct box *first, int width, int *y,
		int cx, int cy, struct box *cont, bool indent,
		pool box_pool, struct box **next_box)
{
	int height, used_height;
	int x0 = 0;
	int x1 = width;
	int x, h, x_previous;
	struct box *left;
	struct box *right;
	struct box *b;
	struct box *split_box = 0;
	struct box *d;
	bool move_y = false;
	int space_before = 0, space_after = 0;
	unsigned int inline_count = 0;

	LOG(("first->text '%.*s', width %i, y %i, cy %i",
			first->length, first->text, width, *y, cy));

	/* find sides at top of line */
	x0 += cx;
	x1 += cx;
	find_sides(cont->float_children, cy, cy, &x0, &x1, &left, &right);
	x0 -= cx;
	x1 -= cx;

	/* get minimum line height from containing block */
	used_height = height = line_height(first->parent->parent->style);

	/* pass 1: find height of line assuming sides at top of line */
	for (x = 0, b = first; x <= x1 - x0 && b != 0; b = b->next) {
		assert(b->type == BOX_INLINE || b->type == BOX_INLINE_BLOCK ||
				b->type == BOX_FLOAT_LEFT ||
				b->type == BOX_FLOAT_RIGHT ||
				b->type == BOX_BR);

		if (b->type == BOX_INLINE_BLOCK) {
			if (b->width == UNKNOWN_WIDTH)
				if (!layout_float(b, width, box_pool))
					return false;
			/** \todo  should margin be included? spec unclear */
			h = b->border[TOP] + b->padding[TOP] + b->height +
					b->padding[BOTTOM] + b->border[BOTTOM];
			if (height < h)
				height = h;
			x += b->margin[LEFT] + b->border[LEFT] +
					b->padding[LEFT] + b->width +
					b->padding[RIGHT] + b->border[RIGHT] +
					b->margin[RIGHT];
		}

		if (b->type == BOX_BR)
			break;

		if (b->type != BOX_INLINE)
			continue;

		if (!b->object && !b->gadget) {
			/* inline non-replaced, 10.3.1 and 10.6.1 */
			b->height = line_height(b->style ? b->style :
					b->parent->parent->style);
			if (height < b->height)
				height = b->height;

			if (b->text) {
				if (b->width == UNKNOWN_WIDTH)
					b->width = nsfont_width(b->font, b->text,
							b->length);
				x += b->width + b->space ?
						b->font->space_width : 0;
			} else
				b->width = 0;

			continue;
		}

		/* inline replaced, 10.3.2 and 10.6.2 */
		assert(b->style);

		/* calculate box width */
		switch (b->style->width.width) {
			case CSS_WIDTH_LENGTH:
				b->width = len(&b->style->width.value.length,
						b->style);
				break;
			case CSS_WIDTH_PERCENT:
				b->width = width *
						b->style->width.value.percent /
						100;
				break;
			case CSS_WIDTH_AUTO:
			default:
				b->width = AUTO;
				break;
		}

		/* height */
		switch (b->style->height.height) {
			case CSS_HEIGHT_LENGTH:
				b->height = len(&b->style->height.length,
						b->style);
				break;
			case CSS_HEIGHT_AUTO:
			default:
				b->height = AUTO;
				break;
		}

		if (b->object) {
			if (b->width == AUTO && b->height == AUTO) {
				b->width = b->object->width;
				b->height = b->object->height;
			} else if (b->width == AUTO) {
				if (b->object->height)
					b->width = b->object->width *
							(float) b->height /
							b->object->height;
				else
					b->width = b->object->width;
			} else if (b->height == AUTO) {
				if (b->object->width)
					b->height = b->object->height *
							(float) b->width /
							b->object->width;
				else
					b->height = b->object->height;
			}
		} else {
			/* form control with no object */
			if (b->width == AUTO)
				b->width = 0;
			if (b->height == AUTO)
				b->height = line_height(b->style ? b->style :
						b->parent->parent->style);
		}

		if (b->object && b->object->type == CONTENT_HTML &&
				 b->width != b->object->available_width) {
			content_reformat(b->object, b->width, b->height);
			if (b->style->height.height == CSS_HEIGHT_AUTO)
				b->height = b->object->height;
		}

		if (height < b->height)
			height = b->height;

		x += b->width;
	}

	/* find new sides using this height */
	x0 = cx;
	x1 = cx + width;
	find_sides(cont->float_children, cy, cy + height, &x0, &x1,
			&left, &right);
	x0 -= cx;
	x1 -= cx;

	if (indent)
		x0 += layout_text_indent(first->parent->parent->style, width);

	if (x1 < x0)
		x1 = x0;

	/* pass 2: place boxes in line: loop body executed at least once */
	for (x = x_previous = 0, b = first; x <= x1 - x0 && b; b = b->next) {
		if (b->type == BOX_INLINE || b->type == BOX_INLINE_BLOCK) {
			x_previous = x;
			x += space_after;
			b->x = x;

			if (b->type == BOX_INLINE_BLOCK) {
				b->x += b->margin[LEFT] + b->border[LEFT];
				x = b->x + b->padding[LEFT] + b->width +
						b->padding[RIGHT] +
						b->border[RIGHT] +
						b->margin[RIGHT];
			} else
				x += b->width;

			space_before = space_after;
			if (b->object)
				space_after = 0;
			else if (b->text)
				space_after = b->space ? b->font->space_width : 0;
			else
				space_after = 0;
			split_box = b;
			move_y = true;
			inline_count++;
/* 			fprintf(stderr, "layout_line:     '%.*s' %li %li\n", b->length, b->text, xp, x); */
		} else if (b->type == BOX_BR) {
			b->x = x;
			b->width = 0;
			b = b->next;
			split_box = 0;
			move_y = true;
			break;

		} else {
			/* float */
			d = b->children;
			d->float_children = 0;
/* 			css_dump_style(b->style); */

			if (!layout_float(d, width, box_pool))
				return false;
			d->x = d->margin[LEFT] + d->border[LEFT];
			d->y = d->margin[TOP] + d->border[TOP];
			b->width = d->margin[LEFT] + d->border[LEFT] +
					d->padding[LEFT] + d->width +
					d->padding[RIGHT] + d->border[RIGHT] +
					d->margin[RIGHT];
			b->height = d->margin[TOP] + d->border[TOP] +
					d->padding[TOP] + d->height +
					d->padding[BOTTOM] + d->border[BOTTOM] +
					d->margin[BOTTOM];
			if (b->width < (x1 - x0) - x || (left == 0 && right == 0 && x == 0)) {
				/* fits next to this line, or this line is empty with no floats */
				if (b->type == BOX_FLOAT_LEFT) {
					b->x = cx + x0;
					x0 += b->width;
					left = b;
				} else {
					b->x = cx + x1 - b->width;
					x1 -= b->width;
					right = b;
				}
				b->y = cy;
/* 				fprintf(stderr, "layout_line:     float fits %li %li, edges %li %li\n", */
/* 						b->x, b->y, x0, x1); */
			} else {
				/* doesn't fit: place below */
				place_float_below(b, width, cx, cy + height + 1, cont);
/* 				fprintf(stderr, "layout_line:     float doesn't fit %li %li\n", b->x, b->y); */
			}
			assert(cont->float_children != b);
			b->next_float = cont->float_children;
			cont->float_children = b;
			split_box = 0;
		}
	}

	if (x1 - x0 < x && split_box) {
		/* the last box went over the end */
		unsigned int i;
		unsigned int space = 0;
		int w;
		struct box * c2;

		x = x_previous;

		if (split_box->type == BOX_INLINE && !split_box->object &&
				!split_box->gadget && split_box->text) {
			for (i = 0; i != split_box->length &&
					split_box->text[i] != ' '; i++)
				;
			if (i != split_box->length)
				space = i;
		}

		/* space != 0 implies split_box->text != 0 */

		if (space == 0)
			w = split_box->width;
		else
			w = nsfont_width(split_box->font, split_box->text, space);

		LOG(("splitting: split_box %p, space %u, w %i, left %p, "
				"right %p, inline_count %u",
				split_box, space, w, left, right,
				inline_count));

		if ((space == 0 || x1 - x0 <= x + space_before + w) &&
				!left && !right && inline_count == 1) {
			/* first word doesn't fit, but no floats and first
			   on line so force in */
			if (space == 0) {
				/* only one word in this box or not text */
				b = split_box->next;
			} else {
				/* cut off first word for this line */
				/* \todo allocate from box_pool */
				c2 = pool_alloc(box_pool, sizeof *c2);
				if (!c2)
					return false;
				memcpy(c2, split_box, sizeof *c2);
				c2->text = strndup(split_box->text + space + 1,
					split_box->length - (space + 1));
				if (!c2->text)
					return false;
				c2->length = split_box->length - (space + 1);
				c2->width = UNKNOWN_WIDTH;
				c2->clone = 1;
				split_box->length = space;
				split_box->width = w;
				split_box->space = 1;
				c2->next = split_box->next;
				split_box->next = c2;
				c2->prev = split_box;
				if (c2->next)
					c2->next->prev = c2;
				else
					c2->parent->last = c2;
				b = c2;
			}
			x += space_before + w;
/* 			fprintf(stderr, "layout_line:     overflow, forcing\n"); */
		} else if (space == 0 || x1 - x0 <= x + space_before + w) {
			/* first word doesn't fit, but full width not
			   available so leave for later */
			b = split_box;
/* 			fprintf(stderr, "layout_line:     overflow, leaving\n"); */
		} else {
			/* fit as many words as possible */
			assert(space != 0);
			space = nsfont_split(split_box->font, split_box->text,
					split_box->length,
					x1 - x0 - x - space_before, &w)
					- split_box->text;
			LOG(("'%.*s' %i %u %i", (int) split_box->length,
					split_box->text, x1 - x0, space, w));
/* 			assert(space == split_box->length || split_box->text[space] = ' '); */
			if (space == 0)
				space = 1;
			/* \todo use box pool */
			c2 = pool_alloc(box_pool, sizeof *c2);
			if (!c2)
				return false;
			memcpy(c2, split_box, sizeof *c2);
			c2->text = strndup(split_box->text + space + 1,
					split_box->length - (space + 1));
			if (!c2->text)
				return false;
			c2->length = split_box->length - (space + 1);
			c2->width = UNKNOWN_WIDTH;
			c2->clone = 1;
			split_box->length = space;
			split_box->width = w;
			split_box->space = 1;
			c2->next = split_box->next;
			split_box->next = c2;
			c2->prev = split_box;
			if (c2->next)
				c2->next->prev = c2;
			else
				c2->parent->last = c2;
			b = c2;
			x += space_before + w;
/* 			fprintf(stderr, "layout_line:     overflow, fit\n"); */
		}
		move_y = true;
	}

	/* set positions */
	switch (first->parent->parent->style->text_align) {
		case CSS_TEXT_ALIGN_RIGHT:  x0 = x1 - x; break;
		case CSS_TEXT_ALIGN_CENTER: x0 = (x0 + (x1 - x)) / 2; break;
		default:		    break; /* leave on left */
	}

	for (d = first; d != b; d = d->next) {
		if (d->type == BOX_INLINE || d->type == BOX_INLINE_BLOCK ||
				d->type == BOX_BR) {
			d->x += x0;
			d->y = *y + d->border[TOP];
			h = d->border[TOP] + d->padding[TOP] + d->height +
					d->padding[BOTTOM] + d->border[BOTTOM];
			if (used_height < h)
				used_height = h;
		}
	}

	assert(b != first || (move_y && 0 < used_height && (left || right)));
	if (move_y) *y += used_height;
	*next_box = b;
	return true;
}


/**
 * Calculate the text-indent length.
 *
 * \param  style  style of block
 * \param  width  width of containing block
 * \return  length of indent
 */

int layout_text_indent(struct css_style *style, int width)
{
	switch (style->text_indent.size) {
		case CSS_TEXT_INDENT_LENGTH:
			return len(&style->text_indent.value.length, style);
		case CSS_TEXT_INDENT_PERCENT:
			return width * style->text_indent.value.percent / 100;
		default:
			return 0;
	}
}


/**
 * Layout the contents of a float or inline block.
 *
 * \param  b      float or inline block box
 * \param  width  available width
 * \param  box_pool  memory pool for any new boxes
 * \return  true on success, false on memory exhaustion
 */

bool layout_float(struct box *b, int width, pool box_pool)
{
	layout_float_find_dimensions(width, b->style, b);
	if (b->type == BOX_TABLE) {
		if (!layout_table(b, width, box_pool))
			return false;
		if (b->margin[LEFT] == AUTO)
			b->margin[LEFT] = 0;
		if (b->margin[RIGHT] == AUTO)
			b->margin[RIGHT] = 0;
	} else
		return layout_block_context(b, box_pool);
	return true;
}


/**
 * Position a float in the first available space.
 *
 * \param  c      float box to position
 * \param  width  available width
 * \param  cx     x coordinate relative to cont to place float right of
 * \param  y      y coordinate relative to cont to place float below
 * \param  cont   ancestor box which defines horizontal space, for floats
 */

void place_float_below(struct box *c, int width, int cx, int y,
		struct box *cont)
{
	int x0, x1, yy = y;
	struct box * left;
	struct box * right;
	do {
		y = yy;
		x0 = cx;
		x1 = cx + width;
		find_sides(cont->float_children, y, y, &x0, &x1, &left, &right);
		if (left != 0 && right != 0) {
			yy = (left->y + left->height < right->y + right->height ?
					left->y + left->height : right->y + right->height) + 1;
		} else if (left == 0 && right != 0) {
			yy = right->y + right->height + 1;
		} else if (left != 0 && right == 0) {
			yy = left->y + left->height + 1;
		}
	} while (!((left == 0 && right == 0) || (c->width < x1 - x0)));

	if (c->type == BOX_FLOAT_LEFT) {
		c->x = x0;
	} else {
		c->x = x1 - c->width;
	}
	c->y = y;
}


/**
 * Layout a table.
 *
 * \param  box_pool  memory pool for any new boxes
 * \return  true on success, false on memory exhaustion
 */

bool layout_table(struct box *table, int available_width,
		pool box_pool)
{
	unsigned int columns = table->columns;  /* total columns */
	unsigned int i;
	unsigned int *row_span;
	int *excess_y;
	int table_width, min_width = 0, max_width = 0;
	int required_width = 0;
	int x;
	int table_height = 0;
	int *xs;  /* array of column x positions */
	int auto_width;
	int spare_width;
	int relative_sum = 0;
	struct box *c;
	struct box *row;
	struct box *row_group;
	struct box **row_span_cell;
	struct column *col;
	struct css_style *style = table->style;

	assert(table->type == BOX_TABLE);
	assert(style);
	assert(table->children && table->children->children);
	assert(columns);

	col = malloc(columns * sizeof col[0]);
	excess_y = malloc(columns * sizeof excess_y[0]);
	row_span = malloc(columns * sizeof row_span[0]);
	row_span_cell = malloc(columns * sizeof row_span_cell[0]);
	xs = malloc((columns + 1) * sizeof xs[0]);
	if (!col || !xs || !row_span || !excess_y || !row_span_cell) {
		free(col);
		free(excess_y);
		free(row_span);
		free(row_span_cell);
		free(xs);
		return false;
	}

	memcpy(col, table->col, sizeof(col[0]) * columns);

	layout_find_dimensions(available_width, style, table->margin,
			table->padding, table->border);

	switch (style->width.width) {
		case CSS_WIDTH_LENGTH:
			table_width = len(&style->width.value.length, style);
			auto_width = table_width;
			break;
		case CSS_WIDTH_PERCENT:
			table_width = available_width *
					style->width.value.percent / 100;
			auto_width = table_width;
			break;
		case CSS_WIDTH_AUTO:
		default:
			table_width = AUTO;
			auto_width = available_width -
					((table->margin[LEFT] == AUTO ?
						0 : table->margin[LEFT]) +
					 table->border[LEFT] +
					 table->padding[LEFT] +
					 table->padding[RIGHT] +
					 table->border[RIGHT] +
					 (table->margin[RIGHT] == AUTO ?
					 	0 : table->margin[RIGHT]));
			break;
	}

	for (i = 0; i != columns; i++) {
		if (col[i].type == COLUMN_WIDTH_FIXED) {
			if (col[i].width < col[i].min)
				col[i].width = col[i].max = col[i].min;
			else
				col[i].min = col[i].max = col[i].width;
			required_width += col[i].width;
		} else if (col[i].type == COLUMN_WIDTH_PERCENT) {
			int width = col[i].width * auto_width / 100;
			required_width += col[i].min < width ? width : col[i].min;
		} else
			required_width += col[i].min;
	}

	LOG(("width %i, min %i, max %i, auto %i, required %i",
			table_width, table->min_width, table->max_width,
			auto_width, required_width));

	if (auto_width < required_width) {
		/* table narrower than required width for columns:
		 * treat percentage widths as maximums */
		for (i = 0; i != columns; i++) {
			if (col[i].type == COLUMN_WIDTH_RELATIVE)
				continue;
			if (col[i].type == COLUMN_WIDTH_PERCENT) {
				col[i].max = auto_width * col[i].width / 100;
				if (col[i].max < col[i].min)
					col[i].max = col[i].min;
			}
			min_width += col[i].min;
			max_width += col[i].max;
		}
	} else {
		/* take percentages exactly */
		for (i = 0; i != columns; i++) {
			if (col[i].type == COLUMN_WIDTH_RELATIVE)
				continue;
			if (col[i].type == COLUMN_WIDTH_PERCENT) {
				int width = auto_width * col[i].width / 100;
				if (width < col[i].min)
					width = col[i].min;
				col[i].min = col[i].width = col[i].max = width;
				col[i].type = COLUMN_WIDTH_FIXED;
			}
			min_width += col[i].min;
			max_width += col[i].max;
		}
	}

	/* allocate relative widths */
	spare_width = auto_width;
	for (i = 0; i != columns; i++) {
		if (col[i].type == COLUMN_WIDTH_RELATIVE)
			relative_sum += col[i].width;
		else if (col[i].type == COLUMN_WIDTH_FIXED)
			spare_width -= col[i].width;
		else
			spare_width -= col[i].min;
	}
	if (relative_sum != 0) {
		if (spare_width < 0)
			spare_width = 0;
		for (i = 0; i != columns; i++) {
			if (col[i].type == COLUMN_WIDTH_RELATIVE) {
				col[i].min = col[i].max = (float) spare_width
						* (float) col[i].width
						/ relative_sum;
				min_width += col[i].min;
				max_width += col[i].max;
			}
		}
	}

	if (auto_width <= min_width) {
		/* not enough space: minimise column widths */
		for (i = 0; i < columns; i++) {
			col[i].width = col[i].min;
		}
		table_width = min_width;
	} else if (max_width <= auto_width) {
		/* more space than maximum width */
		if (table_width == AUTO) {
			/* for auto-width tables, make columns max width */
			for (i = 0; i < columns; i++) {
				col[i].width = col[i].max;
			}
			table_width = max_width;
		} else {
			/* for fixed-width tables, distribute the extra space too */
			unsigned int flexible_columns = 0;
			for (i = 0; i != columns; i++)
				if (col[i].type != COLUMN_WIDTH_FIXED)
					flexible_columns++;
			if (flexible_columns == 0) {
				int extra = (table_width - max_width) / columns;
				for (i = 0; i != columns; i++)
					col[i].width = col[i].max + extra;
			} else {
				int extra = (table_width - max_width) / flexible_columns;
				for (i = 0; i != columns; i++)
					if (col[i].type != COLUMN_WIDTH_FIXED)
						col[i].width = col[i].max + extra;
			}
		}
	} else {
		/* space between min and max: fill it exactly */
		float scale = (float) (auto_width - min_width) /
				(float) (max_width - min_width);
		/* fprintf(stderr, "filling, scale %f\n", scale); */
		for (i = 0; i < columns; i++) {
			col[i].width = col[i].min + (int) (0.5 +
					(col[i].max - col[i].min) * scale);
		}
		table_width = auto_width;
	}

	xs[0] = x = 0;
	for (i = 0; i != columns; i++) {
		x += col[i].width;
		xs[i + 1] = x;
		row_span[i] = 0;
		excess_y[i] = 0;
		row_span_cell[i] = 0;
	}

	/* position cells */
	for (row_group = table->children; row_group != 0; row_group = row_group->next) {
		int row_group_height = 0;
		for (row = row_group->children; row != 0; row = row->next) {
			int row_height = 0;
			for (c = row->children; c != 0; c = c->next) {
				assert(c->style != 0);
				c->width = xs[c->start_column + c->columns] - xs[c->start_column];
				c->float_children = 0;

				c->height = AUTO;
				if (!layout_block_context(c, box_pool)) {
					free(col);
					free(excess_y);
					free(row_span);
					free(row_span_cell);
					free(xs);
					return false;
				}
				if (c->style->height.height == CSS_HEIGHT_LENGTH) {
					/* some sites use height="1" or similar to attempt
					 * to make cells as small as possible, so treat
					 * it as a minimum */
					int h = len(&c->style->height.length, c->style);
					if (c->height < h)
						c->height = h;
				}
				c->x = xs[c->start_column];
				c->y = 0;
				for (i = 0; i != c->columns; i++) {
					row_span[c->start_column + i] = c->rows;
					excess_y[c->start_column + i] = c->height;
					row_span_cell[c->start_column + i] = 0;
				}
				row_span_cell[c->start_column] = c;
				c->height = 0;
			}
			for (i = 0; i != columns; i++)
				if (row_span[i] != 0)
					row_span[i]--;
				else
					row_span_cell[i] = 0;
			if (row->next || row_group->next) {
				/* row height is greatest excess of a cell which ends in this row */
				for (i = 0; i != columns; i++)
					if (row_span[i] == 0 && row_height < excess_y[i])
						row_height = excess_y[i];
			} else {
				/* except in the last row */
				for (i = 0; i != columns; i++)
					if (row_height < excess_y[i])
						row_height = excess_y[i];
			}
			for (i = 0; i != columns; i++) {
				if (row_height < excess_y[i])
					excess_y[i] -= row_height;
				else
					excess_y[i] = 0;
				if (row_span_cell[i] != 0)
					row_span_cell[i]->height += row_height;
			}

			row->x = 0;
			row->y = row_group_height;
			row->width = table_width;
			row->height = row_height;
			row_group_height += row_height;
		}
		row_group->x = 0;
		row_group->y = table_height;
		row_group->width = table_width;
		row_group->height = row_group_height;
		table_height += row_group_height;
	}

	free(col);
	free(excess_y);
	free(row_span);
	free(row_span_cell);
	free(xs);

	table->width = table_width;
	table->height = table_height;

	return true;
}


/**
 * Find min, max widths required by boxes.
 *
 * \param  box  top of tree of boxes
 * \return  true on success, false on memory exhaustion
 *
 * The min_width and max_width fields of each box in the tree are computed.
 */

bool calculate_widths(struct box *box)
{
	struct box *child;
	int min = 0, max = 0, extra_fixed = 0;
	float extra_frac = 0;
	unsigned int side;
	struct css_style *style = box->style;

	assert(box->type == BOX_TABLE_CELL ||
	       box->type == BOX_BLOCK || box->type == BOX_INLINE_BLOCK ||
	       box->type == BOX_FLOAT_LEFT || box->type == BOX_FLOAT_RIGHT);

	/* check if the widths have already been calculated */
	if (box->max_width != UNKNOWN_MAX_WIDTH)
		return true;

	for (child = box->children; child != 0; child = child->next) {
		switch (child->type) {
			case BOX_BLOCK:
			case BOX_TABLE:
				if (!calculate_block_widths(child, &min, &max,
						0))
					return false;
				break;

			case BOX_INLINE_CONTAINER:
				if (!calculate_inline_container_widths(child))
					return false;
				if (min < child->min_width)
					min = child->min_width;
				if (max < child->max_width)
					max = child->max_width;
				break;

			default:
				break;
		}
	}

	/* add margins, border, padding to min, max widths */
	if (style) {
		for (side = 1; side != 5; side += 2) {  /* RIGHT, LEFT */
			if (style->padding[side].padding == CSS_PADDING_LENGTH)
				extra_fixed += len(&style->padding[side].value.length,
						style);
			else if (style->padding[side].padding == CSS_PADDING_PERCENT)
				extra_frac += style->padding[side].value.percent * 0.01;

			if (style->border[side].style != CSS_BORDER_STYLE_NONE)
				extra_fixed += len(&style->border[side].width.value,
						style);

			if (style->margin[side].margin == CSS_MARGIN_LENGTH)
				extra_fixed += len(&style->margin[side].value.length,
						style);
			else if (style->margin[side].margin == CSS_MARGIN_PERCENT)
				extra_frac += style->margin[side].value.percent * 0.01;
		}
	}

	if (1.0 <= extra_frac)
		extra_frac = 0.9;

	box->min_width = (min + extra_fixed) / (1.0 - extra_frac);
	box->max_width = (max + extra_fixed) / (1.0 - extra_frac);

	return true;
}


/**
 * Find min, max widths for a BOX_BLOCK, BOX_INLINE_BLOCK, BOX_FLOAT_*,
 * or BOX_TABLE.
 *
 * \param  box      BLOCK, INLINE_BLOCK, FLOAT, or TABLE box
 * \param  min      current min, updated to new min
 * \param  max      current max, updated to new max
 * \param  max_sum  sum of maximum widths, updated, or 0 if not required
 * \return  true on success, false on memory exhaustion
 */

bool calculate_block_widths(struct box *box, int *min, int *max,
		int *max_sum)
{
	int width;

	if (box->type == BOX_TABLE) {
		if (!calculate_table_widths(box))
			return false;
	} else {
		if (!calculate_widths(box))
			return false;
	}

	if (box->style->width.width == CSS_WIDTH_LENGTH) {
		width = len(&box->style->width.value.length, box->style);
		if (*min < width) *min = width;
		if (*max < width) *max = width;
		if (max_sum) *max_sum += width;
	} else if (box->style->width.width == CSS_WIDTH_AUTO && box->object) {
		/* replaced element */
		if (box->style->height.height == CSS_HEIGHT_AUTO)
			width = box->object->width;
		else
			width = box->object->width *
					(float) len(&box->style->height.length,
					box->style) / box->object->height;
		if (*min < width) *min = width;
		if (*max < width) *max = width;
		if (max_sum) *max_sum += width;
	} else {
		if (*min < box->min_width) *min = box->min_width;
		if (*max < box->max_width) *max = box->max_width;
		if (max_sum) *max_sum += box->max_width;
	}

	return true;
}


/**
 * Find min, max width for an inline container.
 */

bool calculate_inline_container_widths(struct box *box)
{
	struct box *child;
	int min = 0, max = 0, line_max = 0;

	for (child = box->children; child != 0; child = child->next) {
		switch (child->type) {
			case BOX_INLINE:
				if (child->object)
					calculate_inline_replaced_widths(child,
							&min, &max, &line_max);
				else if (child->text)
					calculate_inline_widths(child,
							&min, &line_max);
				break;

			case BOX_INLINE_BLOCK:
				if (!calculate_block_widths(child, &min, &max,
						&line_max))
					return false;
				break;

			case BOX_FLOAT_LEFT:
			case BOX_FLOAT_RIGHT:
				if (!calculate_block_widths(child->children,
						&min, &max, 0))
					return false;
				break;

			case BOX_BR:
				if (max < line_max)
					max = line_max;
				line_max = 0;
				break;

			default:
				assert(0);
		}
	}

	if (max < line_max)
		max = line_max;

	if (box->parent && box->parent->style &&
			(box->parent->style->white_space == CSS_WHITE_SPACE_PRE ||
			 box->parent->style->white_space == CSS_WHITE_SPACE_NOWRAP))
		min = max;

	assert(min <= max);
	box->min_width = min;
	box->max_width = max;

	return true;
}


/**
 * Find min, max width for an inline replaced box.
 */

void calculate_inline_replaced_widths(struct box *box, int *min,
		int *max, int *line_max)
{
	int width;

	if (box->style->width.width == CSS_WIDTH_LENGTH) {
		box->width = len(&box->style->width.value.length, box->style);
		*line_max += box->width;
		if (*min < box->width)
			*min = box->width;
	} else if (box->style->width.width == CSS_WIDTH_AUTO) {
		if (box->style->height.height == CSS_HEIGHT_AUTO)
			width = box->object->width;
		else
			width = box->object->width *
					(float) len(&box->style->height.length,
					box->style) / box->object->height;
		if (*min < width) *min = width;
		if (*max < width) *max = width;
	}
}


/**
 * Find min, max width for an inline text box.
 */

void calculate_inline_widths(struct box *box, int *min, int *line_max)
{
	unsigned int i, j;
	int width;

	/* max = all one line */
	box->width = nsfont_width(box->font, box->text, box->length);
	*line_max += box->width;
	if (box->next && box->space)
		*line_max += box->font->space_width;

	/* min = widest word */
	i = 0;
	do {
		for (j = i; j != box->length && box->text[j] != ' '; j++)
			;
		width = nsfont_width(box->font, box->text + i, j - i);
		if (*min < width) *min = width;
		i = j + 1;
	} while (j != box->length);
}


/**
 * Find min, max widths for a table and determine column width types.
 *
 * \param  table  table box to calculate widths
 * \return  true on success, false on memory exhaustion
 *
 * If table->max_width is not UNKNOWN_MAX_WIDTH, returns with no change to
 * table.
 *
 * If table->col is 0, it is created and filled in completely.
 *
 * If table->col exists, the type and width fields are left unchanged, and the
 * min and max fields are updated.
 *
 * table->min_width and table->max_width are set.
 */

bool calculate_table_widths(struct box *table)
{
	unsigned int i, j;
	struct box *row_group, *row, *cell;
	int width, min_width = 0, max_width = 0;
	struct column *col;

	LOG(("table %p, columns %u", table, table->columns));

	/* check if the widths have already been calculated */
	if (table->max_width != UNKNOWN_MAX_WIDTH)
		return true;

	if ((col = table->col) == NULL) {
		col = table->col = malloc(table->columns * sizeof *col);
		if (!col)
			return false;
		for (i = 0; i != table->columns; i++)
			col[i].type = COLUMN_WIDTH_UNKNOWN;
	}
	for (i = 0; i != table->columns; i++)
		col[i].min = col[i].max = 0;

	assert(table->children && table->children->children);

	/* 1st pass: consider cells with colspan 1 only */
	for (row_group = table->children; row_group;
			row_group = row_group->next) {
		assert(row_group->type == BOX_TABLE_ROW_GROUP);
		for (row = row_group->children; row; row = row->next) {
			assert(row->type == BOX_TABLE_ROW);
			for (cell = row->children; cell; cell = cell->next) {
				assert(cell->type == BOX_TABLE_CELL);
				assert(cell->style);

				if (cell->columns != 1)
					continue;

				if (!calculate_widths(cell))
					return false;
				i = cell->start_column;

				/* update column min, max widths
				 * using cell widths */
				if (col[i].min < cell->min_width)
					col[i].min = cell->min_width;
				if (col[i].max < cell->max_width)
					col[i].max = cell->max_width;

				/* fixed width takes priority over any
				 * other width type */
				if (col[i].type != COLUMN_WIDTH_FIXED &&
						cell->style->width.width ==
						CSS_WIDTH_LENGTH) {
					col[i].type = COLUMN_WIDTH_FIXED;
					col[i].width = len(&cell->style->
							width.value.length,
							cell->style);
					continue;
				}

				if (col[i].type != COLUMN_WIDTH_UNKNOWN)
					continue;

				if (cell->style->width.width ==
						CSS_WIDTH_PERCENT) {
					col[i].type = COLUMN_WIDTH_PERCENT;
					col[i].width = cell->style->
							width.value.percent;
				} else if (cell->style->width.width ==
						CSS_WIDTH_AUTO) {
					col[i].type = COLUMN_WIDTH_AUTO;
				}
			}
		}
	}

	/* 2nd pass: cells which span multiple columns */
	for (row_group = table->children; row_group;
			row_group = row_group->next) {
		for (row = row_group->children; row; row = row->next) {
			for (cell = row->children; cell; cell = cell->next) {
				unsigned int flexible_columns = 0;
				int min = 0, max = 0, fixed_width = 0, cell_min;
				signed long extra;

				if (cell->columns == 1)
					continue;

				if (!calculate_widths(cell))
					return false;
				i = cell->start_column;
				cell_min = cell->min_width;

				/* find min, max width so far of
				 * spanned columns */
				for (j = 0; j != cell->columns; j++) {
					max += col[i + j].max;
					if (col[i + j].type == COLUMN_WIDTH_FIXED) {
						if (col[i + j].min < col[i + j].width)
							min += col[i + j].width;
						else
							min += col[i + j].min;
						fixed_width += col[i + j].width;
					} else {
						min += col[i + j].min;
						flexible_columns++;
					}
				}

				if (cell->style->width.width == CSS_WIDTH_LENGTH) {
					width = len(&cell->style->width.value.length,
							cell->style);
					if (cell_min < width)
						cell_min = width;
				}

				/* distribute extra min, max to spanned columns */
				if (min < cell_min) {
					if (flexible_columns == 0) {
						extra = 1 + (cell_min - min)
								/ cell->columns;
						for (j = 0; j != cell->columns; j++) {
							col[i + j].min += extra;
							if (col[i + j].max < col[i + j].min)
								col[i + j].max = col[i + j].min;
						}
					} else {
						extra = 1 + (cell_min - min)
								/ flexible_columns;
						max = 0;
						for (j = 0; j != cell->columns; j++) {
							if (col[i + j].type != COLUMN_WIDTH_FIXED) {
								col[i + j].min += extra;
								if (col[i + j].max < col[i + j].min)
									col[i + j].max = col[i + j].min;
							}
							max += col[i + j].max;
						}
					}
				}
				if (max < cell->max_width && flexible_columns != 0) {
					extra = 1 + (cell->max_width - max)
							/ flexible_columns;
					for (j = 0; j != cell->columns; j++)
						if (col[i + j].type != COLUMN_WIDTH_FIXED)
							col[i + j].max += extra;
				}
			}
		}
	}

	for (i = 0; i < table->columns; i++) {
		LOG(("col %u, type %i, min %i, max %i, width %i",
				i, col[i].type, col[i].min, col[i].max, col[i].width));
		assert(col[i].min <= col[i].max);
		min_width += col[i].min;
		max_width += col[i].max;
	}
	table->min_width = min_width;
	table->max_width = max_width;

	LOG(("min_width %i, max_width %i", min_width, max_width));

	return true;
}


/**
 * Recursively calculate the descendant_[xy][01] values for a laid-out box tree.
 *
 * \param  box  tree of boxes to update
 */

void layout_calculate_descendant_bboxes(struct box *box)
{
	struct box *child;

	box->descendant_x0 = -box->border[LEFT];
	box->descendant_y0 = -box->border[TOP];
	box->descendant_x1 = box->padding[LEFT] + box->width +
			box->padding[RIGHT] + box->border[RIGHT];
	box->descendant_y1 = box->padding[TOP] + box->height +
			box->padding[BOTTOM] + box->border[BOTTOM];

	for (child = box->children; child; child = child->next) {
		if (child->type == BOX_FLOAT_LEFT ||
				child->type == BOX_FLOAT_RIGHT)
			continue;

		layout_calculate_descendant_bboxes(child);

		if (child->x + child->descendant_x0 < box->descendant_x0)
			box->descendant_x0 = child->x + child->descendant_x0;
		if (box->descendant_x1 < child->x + child->descendant_x1)
			box->descendant_x1 = child->x + child->descendant_x1;
		if (child->y + child->descendant_y0 < box->descendant_y0)
			box->descendant_y0 = child->y + child->descendant_y0;
		if (box->descendant_y1 < child->y + child->descendant_y1)
			box->descendant_y1 = child->y + child->descendant_y1;
	}

	for (child = box->float_children; child; child = child->next_float) {
		if (child->type != BOX_FLOAT_LEFT &&
				child->type != BOX_FLOAT_RIGHT)
			continue;

		layout_calculate_descendant_bboxes(child);

		if (child->x + child->descendant_x0 < box->descendant_x0)
			box->descendant_x0 = child->x + child->descendant_x0;
		if (box->descendant_x1 < child->x + child->descendant_x1)
			box->descendant_x1 = child->x + child->descendant_x1;
		if (child->y + child->descendant_y0 < box->descendant_y0)
			box->descendant_y0 = child->y + child->descendant_y0;
		if (box->descendant_y1 < child->y + child->descendant_y1)
			box->descendant_y1 = child->y + child->descendant_y1;
	}
}