netsurf/render/layout.c

/**
 * $Id: layout.c,v 1.7 2002/06/19 15:17:45 bursa Exp $
 */

#include <assert.h>
#include <ctype.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include "libxml/HTMLparser.h"
#include "css.h"
#include "font.h"
#include "box.h"
#include "utils.h"
#include "layout.h"

/**
 * internal functions
 */

signed long len(struct css_length * length, struct css_style * style);

void layout_block(struct box * box, unsigned long width, struct box * cont,
		unsigned long cx, unsigned long cy);
unsigned long layout_block_children(struct box * box, unsigned long width, struct box * cont,
		unsigned long cx, unsigned long cy);
void find_sides(struct box * fl, unsigned long y0, unsigned long y1,
		unsigned long * x0, unsigned long * x1, struct box ** left, struct box ** right);
void layout_inline_container(struct box * box, unsigned long width, struct box * cont,
		unsigned long cx, unsigned long cy);
signed long line_height(struct css_style * style);
struct box * layout_line(struct box * first, unsigned long width, unsigned long * y,
		unsigned long cy, struct box * cont);
void place_float_below(struct box * c, unsigned long width, unsigned long y, struct box * cont);
void layout_table(struct box * box, unsigned long width, struct box * cont,
		unsigned long cx, unsigned long cy);

/**
 * convert a struct css_length to pixels
 */

signed long len(struct css_length * length, struct css_style * style)
{
	assert(!((length->unit == CSS_UNIT_EM || length->unit == CSS_UNIT_EX) && style == 0));
	switch (length->unit) {
		case CSS_UNIT_EM: return length->value * len(&style->font_size.value.length, 0);
		case CSS_UNIT_EX: return length->value * len(&style->font_size.value.length, 0) * 0.6;
		case CSS_UNIT_PX: return length->value;
		case CSS_UNIT_IN: return length->value * 90.0;
		case CSS_UNIT_CM: return length->value * 35.0;
		case CSS_UNIT_MM: return length->value * 3.5;
		case CSS_UNIT_PT: return length->value * 90.0 / 72.0;
		case CSS_UNIT_PC: return length->value * 90.0 / 6.0;
		default: return 0;
	}
	return 0;
}

/**
 * layout algorithm
 */

/**
 * layout_document -- calculate positions of boxes in a document
 *
 *	doc	root of document box tree
 *	width	page width
 */

void layout_document(struct box * doc, unsigned long width)
{
	doc->float_children = 0;
	layout_block(doc, width, doc, 0, 0);
}


/**
 * layout_block -- position block and recursively layout children
 *
 * 	box	block box to layout
 * 	width	horizontal space available
 * 	cont	ancestor box which defines horizontal space, for inlines
 * 	cx, cy	box position relative to cont
 */

void layout_block(struct box * box, unsigned long width, struct box * cont,
		unsigned long cx, unsigned long cy)
{
	struct css_style * style = box->style;

	assert(box->type == BOX_BLOCK || box->type == BOX_FLOAT);

	switch (style->width.width) {
		case CSS_WIDTH_AUTO:
			/* take all available width */
			box->width = width;
			break;
		case CSS_WIDTH_LENGTH:
			box->width = len(&style->width.value.length, box->style);
			break;
		case CSS_WIDTH_PERCENT:
			box->width = width * style->width.value.percent / 100;
			break;
	}
	box->height = layout_block_children(box, box->width, cont, cx, cy);
	switch (style->height.height) {
		case CSS_HEIGHT_AUTO:
			/* use the computed height */
			break;
		case CSS_HEIGHT_LENGTH:
			box->height = len(&style->height.length, box->style);
			break;
	}
}


/**
 * layout_block_children -- recursively layout block children
 *
 * 	(as above)
 */

unsigned long layout_block_children(struct box * box, unsigned long width, struct box * cont,
		unsigned long cx, unsigned long cy)
{
	struct box * c;
	unsigned long y = 0;

	assert(box->type == BOX_BLOCK || box->type == BOX_FLOAT || box->type == BOX_TABLE_CELL);

	for (c = box->children; c != 0; c = c->next) {
		switch (c->type) {
			case BOX_BLOCK:
				layout_block(c, width, cont, cx, cy + y);
				c->x = 0;
				c->y = y;
				y += c->height;
				break;
			case BOX_INLINE_CONTAINER:
				layout_inline_container(c, width, cont, cx, cy + y);
				c->x = 0;
				c->y = y;
				y += c->height;
				break;
			case BOX_TABLE:
				layout_table(c, width, cont, cx, cy + y);
				c->x = 0;
				c->y = y;
				y += c->height;
				break;
			default:
				fprintf(stderr, "%s -> %s\n",
						box->node ? box->node->name : "()",
						c->node ? c->node->name : "()");
				die("block child not block, table, or inline container");
		}
	}
	return y;
}


/**
 * find_sides -- find left and right margins
 *
 * 	fl	first float in float list
 * 	y0, y1	y range to search
 * 	x1, x1	margins updated
 * 	left	float on left if present
 * 	right	float on right if present
 */

void find_sides(struct box * fl, unsigned long y0, unsigned long y1,
		unsigned long * x0, unsigned long * x1, struct box ** left, struct box ** right)
{
	*left = *right = 0;
	for (; fl; fl = fl->next_float) {
		if (y0 <= fl->y + fl->height && fl->y <= y1) {
			if (fl->style->float_ == CSS_FLOAT_LEFT && *x0 < fl->x + fl->width) {
				*x0 = fl->x + fl->width;
				*left = fl;
			} else if (fl->style->float_ == CSS_FLOAT_RIGHT && fl->x < *x1) {
				*x1 = fl->x;
				*right = fl;
			}
		}
	}
/* 	fprintf(stderr, "find_sides: y0 %li y1 %li => x0 %li x1 %li\n", y0, y1, *x0, *x1); */
}


/**
 * layout_inline_container -- layout lines of text or inline boxes with floats
 *
 *	box	inline container
 *	width	horizontal space available
 *	cont	ancestor box which defines horizontal space, for inlines
 *	cx, cy	box position relative to cont
 */

void layout_inline_container(struct box * box, unsigned long width, struct box * cont,
		unsigned long cx, unsigned long cy)
{
	struct box * c;
	unsigned long y = 0;

	assert(box->type == BOX_INLINE_CONTAINER);

	for (c = box->children; c != 0; ) {
		c = layout_line(c, width, &y, cy + y, cont);
	}

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


signed long line_height(struct css_style * style)
{
	assert(style->line_height.size == CSS_LINE_HEIGHT_LENGTH ||
	       style->line_height.size == CSS_LINE_HEIGHT_ABSOLUTE);

	if (style->line_height.size == CSS_LINE_HEIGHT_LENGTH)
		return len(&style->line_height.value.length, style);
	else
		return style->line_height.value.absolute * len(&style->font_size.value.length, 0);
}


struct box * layout_line(struct box * first, unsigned long width, unsigned long * y,
		unsigned long cy, struct box * cont)
{
	unsigned long height;
	unsigned long x0 = 0;
	unsigned long x1 = width;
	unsigned long x, h, xp;
	struct box * left;
	struct box * right;
	struct box * b;
	struct box * c;
	struct box * d;

/* 	fprintf(stderr, "layout_line: '%.*s' %li %li %li\n", first->length, first->text, width, *y, cy); */

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

	/* get minimum line height from containing block */
	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_FLOAT);
		if (b->type == BOX_INLINE) {
			h = line_height(b->style ? b->style : b->parent->parent->style);
			b->height = h;
			if (h > height) height = h;
			x += font_width(b->style, b->text, b->length);
		}
	}

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

	/* pass 2: place boxes in line */
	for (x = xp = 0, b = first; x < x1 - x0 && b != 0; b = b->next) {
		if (b->type == BOX_INLINE) {
			b->x = x;
			xp = x;
			b->width = font_width(b->style, b->text, b->length);
			x += b->width;
			c = b;
/* 			fprintf(stderr, "layout_line:     '%.*s' %li %li\n", b->length, b->text, xp, x); */
		} else {
			b->float_children = 0;
			css_dump_style(b->style);
			layout_block(b, width, b, 0, 0);
			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->style->float_ == CSS_FLOAT_LEFT) {
					b->x = x0;
					x0 += b->width;
					left = b;
				} else {
					b->x = 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, cy + height + 1, cont);
/* 				fprintf(stderr, "layout_line:     float doesn't fit %li %li\n", b->x, b->y); */
			}
			b->next_float = cont->float_children;
			cont->float_children = b;
		}
	}

	if (x1 - x0 < x) {
		/* the last box went over the end */
		char * space = strchr(c->text, ' ');
		char * space2 = space;
		unsigned long w = font_width(c->style, c->text, space - c->text), wp = w;
		struct box * c2;

		if (x1 - x0 < xp + w && left == 0 && right == 0 && c == first) {
			/* first word doesn't fit, but no floats and first on line so force in */
			c2 = memcpy(xcalloc(1, sizeof(struct box)), c, sizeof(struct box));
			c2->text = space + 1;
			c2->length = c->length - (c2->text - c->text);
			c->length = space - c->text;
			c2->next = c->next;
			c->next = c2;
			b = c2;
/* 			fprintf(stderr, "layout_line:     overflow, forcing\n"); */
		} else if (x1 - x0 < xp + w) {
			/* first word doesn't fit, but full width not available so leave for later */
			b = c;
/* 			fprintf(stderr, "layout_line:     overflow, leaving\n"); */
		} else {
			/* fit as many words as possible */
			while (xp + w < x1 - x0) {
/* 				fprintf(stderr, "%li + %li = %li < %li = %li - %li\n", */
/* 						xp, w, xp + w, x1 - x0, x1, x0); */
				space = space2;
				wp = w;
				space2 = strchr(space + 1, ' ');
				w = font_width(c->style, c->text, space2 - c->text);
			}
			c2 = memcpy(xcalloc(1, sizeof(struct box)), c, sizeof(struct box));
			c2->text = space + 1;
			c2->length = c->length - (c2->text - c->text);
			c->length = space - c->text;
			c2->next = c->next;
			c->next = c2;
			b = c2;
/* 			fprintf(stderr, "layout_line:     overflow, fit\n"); */
		}
		c->width = wp;
		x = xp + wp;
	}

	/* 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:                    /* leave on left */
	}
	for (d = first; d != b; d = d->next) {
		if (d->type == BOX_INLINE) {
			d->x += x0;
			d->y = *y;
		}
	}

	*y += height + 1;
	return b;
}



void place_float_below(struct box * c, unsigned long width, unsigned long y, struct box * cont)
{
	unsigned long x0, x1, yy = y;
	struct box * left;
	struct box * right;
	do {
		y = yy;
		x0 = 0;
		x1 = 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->style->float_ == CSS_FLOAT_LEFT) {
		c->x = x0;
	} else {
		c->x = x1 - c->width;
	}
	c->y = y;
}



/**
 * layout a table
 *
 * this is the fixed table layout algorithm,
 * <http://www.w3.org/TR/REC-CSS2/tables.html#fixed-table-layout>
 */

void layout_table(struct box * table, unsigned long width, struct box * cont,
		unsigned long cx, unsigned long cy)
{
	unsigned int columns;  /* total columns */
	unsigned int auto_columns;  /* number of columns with auto width */
	unsigned long table_width;
	unsigned long used_width = 0;  /* width used by fixed or percent columns */
	unsigned long auto_width;  /* width of each auto column (all equal) */
	unsigned long extra_width = 0;  /* extra width for each column if table is wider than columns */
	unsigned long x;
	unsigned long y = 0;
	unsigned long * xs;
	unsigned int i;
	struct box * c;
	struct box * r;

	assert(table->type == BOX_TABLE);

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

	/* calculate column statistics */
	for (columns = 0, auto_columns = 0, c = table->children->children;
			c != 0; c = c->next) {
		assert(c->type == BOX_TABLE_CELL);
		switch (c->style->width.width) {
			case CSS_WIDTH_LENGTH:
				used_width += len(&c->style->width.value.length, c->style);
				break;
			case CSS_WIDTH_PERCENT:
				used_width += table_width * c->style->width.value.percent / 100;
				break;
			case CSS_WIDTH_AUTO:
				auto_columns++;
				break;
		}
		columns++;
	}

	if (auto_columns == 0 && table->style->width.width != CSS_WIDTH_AUTO)
		extra_width = (table_width - used_width) / columns;
	else if (auto_columns != 0)
		auto_width = (table_width - used_width) / auto_columns;

	/*printf("%i %i %i %i %i\n", table_width, columns, auto_columns, used_width, auto_width);*/

	/* find column widths */
	xs = xcalloc(columns + 1, sizeof(*xs));
	xs[0] = x = 0;
	for (i = 1, c = table->children->children; c != 0; i++, c = c->next) {
		switch (c->style->width.width) {
			case CSS_WIDTH_LENGTH:
				x += len(&c->style->width.value.length, c->style) + extra_width;
				break;
			case CSS_WIDTH_PERCENT:
				x += table_width * c->style->width.value.percent / 100 + extra_width;
				break;
			case CSS_WIDTH_AUTO:
				x += auto_width;
				break;
		}
		xs[i] = x;
		/*printf("%i ", x);*/
	}
	/*printf("\n");*/

	if (auto_columns == 0 && table->style->width.width == CSS_WIDTH_AUTO)
		table_width = used_width;

	/* position cells */
	for (r = table->children; r != 0; r = r->next) {
		unsigned long height = 0;
		for (i = 0, c = r->children; c != 0; i++, c = c->next) {
			c->width = xs[i+1] - xs[i];
			c->float_children = 0;
			c->height = layout_block_children(c, c->width, c, 0, 0);
			switch (c->style->height.height) {
				case CSS_HEIGHT_AUTO:
					break;
				case CSS_HEIGHT_LENGTH:
					c->height = len(&c->style->height.length, c->style);
					break;
			}
			c->x = xs[i];
			c->y = 0;
			if (c->height > height) height = c->height;
		}
		r->x = 0;
		r->y = y;
		r->width = table_width;
		r->height = height;
		y += height;
	}

	free(xs);

	table->width = table_width;
	table->height = y;
}