netsurf/desktop/textarea.c

/*
 * Copyright 2006 John-Mark Bell <jmb@netsurf-browser.org>
 * Copyright 2009 Paul Blokus <paul_pl@users.sourceforge.net>
 *
 * This file is part of NetSurf, http://www.netsurf-browser.org/
 *
 * NetSurf 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; version 2 of the License.
 *
 * NetSurf 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/>.
 */

/** \file
 * Single/Multi-line UTF-8 text area (implementation)
 */

#include <stdint.h>
#include <string.h>
#include "css/css.h"
#include "desktop/textarea.h"
#include "desktop/textinput.h"
#include "desktop/plotters.h"
#include "render/font.h"
#include "utils/log.h"
#include "utils/utf8.h"
#include "utils/utils.h"

#define MARGIN_LEFT 2
#define MARGIN_RIGHT 2
#define CARET_COLOR 0x000000
/* background color for readonly textarea */
#define READONLY_BG 0xD9D9D9
#define BACKGROUND_COL 0xFFFFFF
#define BORDER_COLOR 0x000000
#define SELECTION_COL 0xFFDDDD

static plot_style_t pstyle_fill_selection = { 
    .fill_type = PLOT_OP_TYPE_SOLID,
    .fill_colour = SELECTION_COL,
};

static plot_style_t pstyle_stroke_border = { 
    .stroke_type = PLOT_OP_TYPE_SOLID,
    .stroke_colour = BORDER_COLOR,
    .stroke_width = 1,
};

static plot_style_t pstyle_stroke_caret = { 
    .stroke_type = PLOT_OP_TYPE_SOLID,
    .stroke_colour = CARET_COLOR,
    .stroke_width = 1,
};

struct line_info {
	unsigned int b_start;		/**< Byte offset of line start */
	unsigned int b_length;		/**< Byte length of line */
};

struct text_area {

	int x, y;			/**< Coordinates of the widget
					 * (top left corner) with respect to
					 * canvas origin(these don't change
					 * it is the canvas which gets
					 * scrolled)
					 */
					
	int scroll_x, scroll_y;		/**< scroll offsets of the textarea
					 * content
					 */
	
	unsigned int flags;		/**< Textarea flags */
	int vis_width;			/**< Visible width, in pixels */
	int vis_height;			/**< Visible height, in pixels */

	char *text;			/**< UTF-8 text */
	unsigned int text_alloc;	/**< Size of allocated text */
	unsigned int text_len;		/**< Length of text, in bytes */
	unsigned int text_utf8_len;	/**< Length of text, in characters
					 * without the trailing NUL
					 */
	struct {
		int line;		/**< Line caret is on */
		int char_off;		/**< Character index of caret within the
					 * specified line
					 */
	} caret_pos;
	
	int selection_start;	/**< Character index of sel start(inclusive) */
	int selection_end;	/**< Character index of sel end(exclusive) */

	struct css_style *style;	/**<  Text style */	
	
	int line_count;			/**< Count of lines */
#define LINE_CHUNK_SIZE 16
	struct line_info *lines;	/**< Line info array */
	int line_height;		/**< Line height obtained from style */
	
	/** Callback functions for a redraw request */
	textarea_start_redraw_callback redraw_start_callback;
	textarea_start_redraw_callback redraw_end_callback;
	 
	void *data; /** < Callback data for both callback functions */
	
	int drag_start_char; /**< Character index at which the drag was
			      * started
			      */
};


static bool textarea_insert_text(struct text_area *ta, unsigned int index,
		const char *text);
static bool textarea_replace_text(struct text_area *ta, unsigned int start,
		unsigned int end, const char *text);
static bool textarea_reflow(struct text_area *ta, unsigned int line);
static unsigned int textarea_get_xy_offset(struct text_area *ta, int x, int y);
static bool textarea_set_caret_xy(struct text_area *ta, int x, int y);
static bool textarea_scroll_visible(struct text_area *ta);
static bool textarea_select(struct text_area *ta, int c_start, int c_end);
static void textarea_normalise_text(struct text_area *ta,
		unsigned int b_start, unsigned int b_len);

/**
 * Create a text area
 *
 * \param x X coordinate of left border
 * \param y Y coordinate of top border
 * \param width width of the text area
 * \param height width of the text area
 * \param flags text area flags
 * \param style css style (font style properties are used only)
 * \param redraw_start_callback will be called when textarea wants to redraw
 * \param redraw_end_callback will be called when textarea finisjes redrawing
 * \param data user specified data which will be passed to redraw callbacks
 * \return Opaque handle for textarea or 0 on error
 */
struct text_area *textarea_create(int x, int y, int width, int height, 
		unsigned int flags, const struct css_style *style,
		textarea_start_redraw_callback redraw_start_callback,
		textarea_end_redraw_callback redraw_end_callback, void *data)
{
	struct text_area *ret;

	if (redraw_start_callback == NULL || redraw_end_callback == NULL) {
		LOG(("no callback provided"));
		return NULL;
	}
	
	ret = malloc(sizeof(struct text_area));
	if (ret == NULL) {
		LOG(("malloc failed"));
		return NULL;
	}

	ret->redraw_start_callback = redraw_start_callback;
	ret->redraw_end_callback = redraw_end_callback;
	ret->data = data;
	ret->x = x;
	ret->y = y;
	ret->vis_width = width;
	ret->vis_height = height;
	ret->scroll_x = 0;
	ret->scroll_y = 0;
	ret->drag_start_char = 0;
	
	
	ret->flags = flags;
	ret->text = malloc(64);
	if (ret->text == NULL) {
		LOG(("malloc failed"));
		free(ret);
		return NULL;
	}
	ret->text[0] = '\0';
	ret->text_alloc = 64;
	ret->text_len = 1;
	ret->text_utf8_len = 0;
	
	ret->style = malloc(sizeof(struct css_style));
	if (ret->style == NULL) {
		LOG(("malloc failed"));
		free(ret->text);
		free(ret);
		return NULL;
	}
	memcpy(ret->style, style, sizeof(struct css_style));
	ret->line_height = css_len2px(&(style->line_height.value.length),
			style);
	
	ret->caret_pos.line = ret->caret_pos.char_off = 0;
	ret->selection_start = -1;
	ret->selection_end = -1;
	
	ret->line_count = 0;
	ret->lines = NULL;

	return ret;
}


/**
 * Change the position of a textarea. The text area is redrawn
 *
 * \param ta  the textarea to change position of
 * \param x   X coordinate of the the new position
 * \param y   Y coordinate of the the new position
 */
void textarea_set_position(struct text_area *ta, int x, int y)
{
	ta->x = x;
	ta->y = y;	
	ta->redraw_start_callback(ta->data);
	textarea_redraw(ta, ta->x, ta->y, ta->x + ta->vis_width,
			ta->y + ta->vis_height);
	textarea_set_caret(ta, textarea_get_caret(ta));
	ta->redraw_start_callback(ta->data);	
}


/**
 * Destroy a text area
 *
 * \param ta Text area to destroy
 */
void textarea_destroy(struct text_area *ta)
{
	free(ta->text);
	free(ta->style);
	free(ta->lines);
	free(ta);
}


/**
 * Set the text in a text area, discarding any current text
 *
 * \param ta Text area
 * \param text UTF-8 text to set text area's contents to
 * \return true on success, false on memory exhaustion
 */
bool textarea_set_text(struct text_area *ta, const char *text)
{
	unsigned int len = strlen(text) + 1;

	if (len >= ta->text_alloc) {
		char *temp = realloc(ta->text, len + 64);
		if (temp == NULL) {
			LOG(("realloc failed"));
			return false;
		}
		ta->text = temp;
		ta->text_alloc = len + 64;
	}

	memcpy(ta->text, text, len);
	ta->text_len = len;
	ta->text_utf8_len = utf8_length(ta->text);
	
	textarea_normalise_text(ta, 0, len);
	
	return textarea_reflow(ta, 0);
}


/**
 * Extract the text from a text area
 *
 * \param ta Text area
 * \param buf Pointer to buffer to receive data, or NULL
 *            to read length required
 * \param len Length (bytes) of buffer pointed to by buf, or 0 to read length
 * \return Length (bytes) written/required or -1 on error
 */
int textarea_get_text(struct text_area *ta, char *buf, unsigned int len)
{
	if (buf == NULL && len == 0) {
		/* want length */
		return ta->text_len;
	}

	if (len < ta->text_len) {
		LOG(("buffer too small"));
		return -1;
	}

	memcpy(buf, ta->text, ta->text_len);

	return ta->text_len;
}


/**
 * Insert text into the text area
 *
 * \param ta Text area
 * \param index 0-based character index to insert at
 * \param text UTF-8 text to insert
 * \return false on memory exhaustion, true otherwise
 */
bool textarea_insert_text(struct text_area *ta, unsigned int index,
		const char *text)
{
	unsigned int b_len = strlen(text);
	size_t b_off;

	if (ta->flags & TEXTAREA_READONLY)
		return true;

	/* Find insertion point */
	if (index > ta->text_utf8_len)
		index = ta->text_utf8_len;

	/* find byte offset of insertion point */
	for (b_off = 0; index-- > 0;
			b_off = utf8_next(ta->text, ta->text_len, b_off))
		; /* do nothing */

	if (b_len + ta->text_len >= ta->text_alloc) {
		char *temp = realloc(ta->text, b_len + ta->text_len + 64);
		if (temp == NULL) {
			LOG(("realloc failed"));
			return false;
		}

		ta->text = temp;
		ta->text_alloc = b_len + ta->text_len + 64;
	}

	/* Shift text following up */
	memmove(ta->text + b_off + b_len, ta->text + b_off,
			ta->text_len - b_off);
	/* Insert new text */
	memcpy(ta->text + b_off, text, b_len);
	ta->text_len += b_len;
	ta->text_utf8_len += utf8_length(text);
	
	textarea_normalise_text(ta, b_off, b_len);	

	/** \todo calculate line to reflow from */
	return textarea_reflow(ta, 0);
	
}


/**
 * Replace text in a text area
 *
 * \param ta Text area
 * \param start Start character index of replaced section (inclusive)
 * \param end End character index of replaced section (exclusive)
 * \param text UTF-8 text to insert
 * \return false on memory exhaustion, true otherwise
 */
bool textarea_replace_text(struct text_area *ta, unsigned int start,
		unsigned int end, const char *text)
{
	unsigned int b_len = strlen(text);
	size_t b_start, b_end, diff;

	if (ta->flags & TEXTAREA_READONLY)
		return true;

	if (start > ta->text_utf8_len)
		start = ta->text_utf8_len;
	if (end > ta->text_utf8_len)
		end = ta->text_utf8_len;

	if (start == end)
		return textarea_insert_text(ta, start, text);

	if (start > end)
		return false;

	diff = end - start;

	/* find byte offset of replace start */
	for (b_start = 0; start-- > 0;
			b_start = utf8_next(ta->text, ta->text_len, b_start))
		; /* do nothing */

	/* find byte length of replaced text */
	for (b_end = b_start; diff-- > 0;
			b_end = utf8_next(ta->text, ta->text_len, b_end))
		; /* do nothing */

	if (b_len + ta->text_len - (b_end - b_start) >= ta->text_alloc) {
		char *temp = realloc(ta->text,
			b_len + ta->text_len - (b_end - b_start) + 64);
		if (temp == NULL) {
			LOG(("realloc failed"));
			return false;
		}

		ta->text = temp;
		ta->text_alloc =
			b_len + ta->text_len - (b_end - b_start) + 64;
	}

	/* Shift text following to new position */
	memmove(ta->text + b_start + b_len, ta->text + b_end,
			ta->text_len - b_end);

	/* Insert new text */
	memcpy(ta->text + b_start, text, b_len);

	ta->text_len += b_len - (b_end - b_start);	
	ta->text_utf8_len = utf8_length(ta->text);
	textarea_normalise_text(ta, b_start, b_len);

	/** \todo calculate line to reflow from */
	return textarea_reflow(ta, 0);
}


/**
 * Set the caret's position
 *
 * \param ta 		Text area
 * \param caret 	0-based character index to place caret at, -1 removes
 * 			the caret
 * \return true on success false otherwise
 */
bool textarea_set_caret(struct text_area *ta, int caret)
{
	unsigned int c_len;
	unsigned int b_off;
	int i;
	int index;
	int x, y;
	int x0, y0, x1, y1;
	int height;
	
		
	if (ta->flags & TEXTAREA_READONLY)
		return true;
	
	ta->redraw_start_callback(ta->data);
	
	c_len = ta->text_utf8_len;

	if (caret != -1 && (unsigned)caret > c_len)
		caret = c_len;

	height = css_len2px(&(ta->style->font_size.value.length),
			ta->style);
	/* Delete the old caret */
	if (ta->caret_pos.char_off != -1) {
		index = textarea_get_caret(ta);
		if (index == -1)
			return false;
		
		/* the redraw might happen in response to a text-change and
		the caret position might be beyond the current text */
		if ((unsigned)index > c_len)
			index = c_len;
	
		/* find byte offset of caret position */
		for (b_off = 0; index-- > 0;
				b_off = utf8_next(ta->text,
				ta->text_len, b_off))
			; /* do nothing */
	
		nsfont.font_width(ta->style,
				ta->text +
				ta->lines[ta->caret_pos.line].b_start,
				b_off - ta->lines[ta->caret_pos.line].b_start,
    				&x);
		
		x += ta->x + MARGIN_LEFT - ta->scroll_x;
		
		y = ta->line_height * ta->caret_pos.line + ta->y - ta->scroll_y;

		textarea_redraw(ta, x - 1, y - 1, x + 1, y + height + 1);
	}
	
	/* check if the caret has to be drawn at all */
	if (caret != -1) {
		/* Find byte offset of caret position */
		for (b_off = 0; caret > 0; caret--)
			b_off = utf8_next(ta->text, ta->text_len, b_off);
	
		/* Now find line in which byte offset appears */
		for (i = 0; i < ta->line_count - 1; i++)
			if (ta->lines[i + 1].b_start > b_off)
				break;
			
		ta->caret_pos.line = i;
	
		/* Now calculate the char. offset of the caret in this line */
		for (c_len = 0, ta->caret_pos.char_off = 0;
				c_len < b_off - ta->lines[i].b_start;
				c_len = utf8_next(ta->text +
						ta->lines[i].b_start,
						ta->lines[i].b_length, c_len))
			ta->caret_pos.char_off++;
	
		if (textarea_scroll_visible(ta))
			textarea_redraw(ta, ta->x, ta->y, ta->x + ta->vis_width,
					ta->y + ta->vis_height);
		
		/* Finally, redraw the caret */
		index = textarea_get_caret(ta);
		if (index == -1)
			return false;
	
		/* find byte offset of caret position */
		for (b_off = 0; index-- > 0;
				b_off = utf8_next(ta->text,
						ta->text_len, b_off))
			; /* do nothing */
	
		nsfont.font_width(ta->style,
				ta->text +
				ta->lines[ta->caret_pos.line].b_start,
				b_off - ta->lines[ta->caret_pos.line].b_start,
    				&x);
		
		x += ta->x + MARGIN_LEFT - ta->scroll_x;
		
		y = ta->line_height * ta->caret_pos.line + ta->y - ta->scroll_y;
	
		x0 = max(x - 1, ta->x + MARGIN_LEFT);
		y0 = max(y - 1, ta->y);
		x1 = min(x + 1, ta->x + ta->vis_width - MARGIN_RIGHT);
		y1 = min(y + height + 1, ta->y + ta->vis_height);
		
		plot.clip(x0, y0, x1, y1);
		plot.line(x, y, x, y + height, &pstyle_stroke_caret);
	}
	ta->redraw_end_callback(ta->data);	
	
	return true;
}


/**
 * get character offset from the beginning of the text for some coordinates
 *
 * \param ta		Text area
 * \param x		X coordinate
 * \param y		Y coordinate
 * \return		character offset
 */
unsigned int textarea_get_xy_offset(struct text_area *ta, int x, int y)
{
	size_t b_off, temp;
	unsigned int c_off;
	int line;

	if (!ta->line_count)
		return 0;

	x = x - ta->x - MARGIN_LEFT + ta->scroll_x;
	y = y - ta->y + ta->scroll_y;

	if (x < 0)
		x = 0;
	
	line = y / ta->line_height;

	if (line < 0)
		line = 0;
	if (ta->line_count - 1 < line)
		line = ta->line_count - 1;

	nsfont.font_position_in_string(ta->style,
			ta->text + ta->lines[line].b_start, 
	   		ta->lines[line].b_length, x, &b_off, &x);
	
	/* If the calculated byte offset corresponds with the number of bytes
	 * in the line, and the line has been soft-wrapped, then ensure the
	 * caret offset is before the trailing space character, rather than
	 * after it. Otherwise, the caret will be placed at the start of the
	 * following line, which is undesirable.
	 */
	if (b_off == (unsigned)ta->lines[line].b_length &&
			ta->text[ta->lines[line].b_start +
			ta->lines[line].b_length - 1] == ' ')
		b_off--;

	for (temp = 0, c_off = 0; temp < b_off + ta->lines[line].b_start;
			temp = utf8_next(ta->text, ta->text_len, temp))
		c_off++;

	return c_off;
}


/**
 * Set the caret's position
 *
 * \param ta Text area
 * \param x X position of caret in a window relative to text area top left
 * \param y Y position of caret in a window relative to text area top left
 * \return true on success false otherwise
 */
bool textarea_set_caret_xy(struct text_area *ta, int x, int y)
{
	unsigned int c_off;
	
	if (ta->flags & TEXTAREA_READONLY)
		return true;
	
	c_off = textarea_get_xy_offset(ta, x, y);
	return textarea_set_caret(ta, c_off);
}


/**
 * Get the caret's position
 *
 * \param ta Text area
 * \return 0-based character index of caret location, or -1 on error
 */
int textarea_get_caret(struct text_area *ta)
{
	unsigned int c_off = 0, b_off;

	
	/* if the text is a trailing NUL only */
	if (ta->text_utf8_len == 0)
		return 0;
	
	/* Calculate character offset of this line's start */
	for (b_off = 0; b_off < ta->lines[ta->caret_pos.line].b_start;
			b_off = utf8_next(ta->text, ta->text_len, b_off))
		c_off++;

	return c_off + ta->caret_pos.char_off;
}

/**
 * Reflow a text area from the given line onwards
 *
 * \param ta Text area to reflow
 * \param line Line number to begin reflow on
 * \return true on success false otherwise
 */
bool textarea_reflow(struct text_area *ta, unsigned int line)
{
	char *text;
	unsigned int len;
	size_t b_off;
	int x;
	char *space;
	unsigned int line_count = 0;

	/** \todo pay attention to line parameter */
	/** \todo create horizontal scrollbar if needed */

	ta->line_count = 0;

	if (ta->lines == NULL) {
		ta->lines =
			malloc(LINE_CHUNK_SIZE * sizeof(struct line_info));
		if (ta->lines == NULL) {
			LOG(("malloc failed"));
			return false;
		}
	}

	if (!(ta->flags & TEXTAREA_MULTILINE)) {
		/* Single line */
		ta->lines[line_count].b_start = 0;
		ta->lines[line_count++].b_length = ta->text_len - 1;

		ta->line_count = line_count;

		return true;
	}

	for (len = ta->text_len - 1, text = ta->text; len > 0;
			len -= b_off, text += b_off) {

		nsfont.font_split(ta->style, text, len,
				ta->vis_width - MARGIN_LEFT - MARGIN_RIGHT,
				&b_off, &x);
		
		if (line_count > 0 && line_count % LINE_CHUNK_SIZE == 0) {
			struct line_info *temp = realloc(ta->lines,
					(line_count + LINE_CHUNK_SIZE) *
					sizeof(struct line_info));
			if (temp == NULL) {
				LOG(("realloc failed"));
				return false;
			}

			ta->lines = temp;
		}

		/* handle LF */
		for (space = text; space <= text + b_off; space++) {
			if (*space == '\n')
				break;
		}

		if (space <= text + b_off) {
			/* Found newline; use it */
			ta->lines[line_count].b_start = text - ta->text;
			ta->lines[line_count++].b_length = space - text;

			b_off = space + 1 - text;

			if (len - b_off == 0) {
				/* reached end of input => add last line */
				ta->lines[line_count].b_start =
						text + b_off - ta->text;
				ta->lines[line_count++].b_length = 0;
			}

			continue;
		}

		if (len - b_off > 0) {
			/* find last space (if any) */
			for (space = text + b_off; space > text; space--)
				if (*space == ' ')
					break;

			if (space != text)
				b_off = space + 1 - text;
		}

		ta->lines[line_count].b_start = text - ta->text;
		ta->lines[line_count++].b_length = b_off;
	}

	ta->line_count = line_count;
	
	return true;
}

/**
 * Handle redraw requests for text areas
 *
 * \param redraw Redraw request block
 * \param x0	 left X coordinate of redraw area
 * \param y0	 top Y coordinate of redraw area
 * \param x1	 right X coordinate of redraw area
 * \param y1	 bottom Y coordinate of redraw area
 */
void textarea_redraw(struct text_area *ta, int x0, int y0, int x1, int y1)
{
	int line0, line1, line;
	int chars, offset;
	unsigned int c_pos, c_len, b_start, b_end, line_len;
	char *line_text;
        plot_style_t plot_style_fill_bg = { 
            .fill_type = PLOT_OP_TYPE_SOLID,
            .fill_colour = BACKGROUND_COL,
        };

	
	if (x1 < ta->x || x0 > ta->x + ta->vis_width || y1 < ta->y ||
		   y0 > ta->y + ta->vis_height)
		/* Textarea outside the clipping rectangle */
		return;
	
	if (ta->lines == NULL)
		/* Nothing to redraw */
		return;

        if (ta->flags & TEXTAREA_READONLY)
            plot_style_fill_bg.fill_colour = READONLY_BG;
	
	line0 = (y0 - ta->y + ta->scroll_y) / ta->line_height - 1;
	line1 = (y1 - ta->y + ta->scroll_y) / ta->line_height + 1;

	if (line0 < 0)
		line0 = 0;
	if (line1 < 0)
		line1 = 0;
	if (ta->line_count - 1 < line0)
		line0 = ta->line_count - 1;
	if (ta->line_count - 1 < line1)
		line1 = ta->line_count - 1;
	if (line1 < line0)
		line1 = line0;

	if (x0 < ta->x)
		x0 = ta->x;
	if (y0 < ta->y)
		y0 = ta->y;
	if (x1 > ta->x + ta->vis_width)
		x1 = ta->x + ta->vis_width;
	if (y1 > ta->y + ta->vis_height)
		y1 = ta->y + ta->vis_height;
	
	plot.clip(x0, y0, x1, y1);
	plot.rectangle(x0, y0, x1, y1, &plot_style_fill_bg);
	plot.rectangle(ta->x, ta->y, 
		       ta->x + ta->vis_width - 1, ta->y + ta->vis_height - 1, 
		       &pstyle_stroke_border);
	
	if (x0 < ta->x + MARGIN_LEFT)
		x0 = ta->x + MARGIN_LEFT;
	if (x1 > ta->x + ta->vis_width - MARGIN_RIGHT)
		x1 = ta->x + ta->vis_width - MARGIN_RIGHT;
	plot.clip(x0, y0, x1, y1);
		
	if (line0 > 0)
		c_pos = utf8_bounded_length(ta->text,
				ta->lines[line0].b_start - 1);
	else
		c_pos = 0;
	
	for (line = line0; (line <= line1) &&
			(ta->y + line * ta->line_height <= y1 + ta->scroll_y);
			line++) {
		if (ta->lines[line].b_length == 0)
			continue;

		c_len = utf8_bounded_length(
				&(ta->text[ta->lines[line].b_start]),
				ta->lines[line].b_length);
		
		/* if there is a newline between the lines count it too */
		if (line < ta->line_count - 1 && ta->lines[line + 1].b_start !=
				ta->lines[line].b_start +
				ta->lines[line].b_length)
			c_len++;
		
		/* check if a part of the line is selected, won't happen if no
		  selection (ta->selection_end = -1) */
		if (ta->selection_end != -1 &&
				c_pos < (unsigned)ta->selection_end &&
				c_pos + c_len > (unsigned)ta->selection_start) {
			
			/* offset from the beginning of the line */
			offset = ta->selection_start - c_pos;
			chars = ta->selection_end - c_pos -
					(offset > 0 ? offset:0);
									
			line_text = &(ta->text[ta->lines[line].b_start]);
			line_len = ta->lines[line].b_length;
			
			if (offset > 0) {
				
				/* find byte start of the selected part */
				for (b_start = 0; offset > 0; offset--)
					b_start = utf8_next(line_text,
							line_len,
       							b_start);
				nsfont.font_width(ta->style, line_text,
						b_start, &x0);
				x0 += ta->x + MARGIN_LEFT;
			}
			else {
				x0 = ta->x + MARGIN_LEFT;
				b_start = 0;
			}
			
			
			if (chars >= 0) {
				
				/* find byte end of the selected part */
				for (b_end = b_start; chars > 0 &&
						b_end < line_len;
						chars--) {
					b_end = utf8_next(line_text, line_len,
       							b_end);
				}
			}
			else
				b_end = ta->lines[line].b_length;
			
			b_end -= b_start;
			nsfont.font_width(ta->style,
					&(ta->text[ta->lines[line].b_start +
					b_start]),
					b_end, &x1);
			x1 += x0;
			plot.rectangle(x0 - ta->scroll_x, ta->y +
				       line * ta->line_height
				       + 1 - ta->scroll_y,
				       x1 - ta->scroll_x,
				       ta->y + (line + 1) * ta->line_height -
				       1 - ta->scroll_y,
				       &pstyle_fill_selection);
			
		}
		
		c_pos += c_len;

		y0 = ta->y + line * ta->line_height + 0.75 * ta->line_height;
		
		plot.text(ta->x + MARGIN_LEFT - ta->scroll_x, y0 - ta->scroll_y,
			  	ta->style,
			  	ta->text + ta->lines[line].b_start,
			   	ta->lines[line].b_length,
			   	(ta->flags & TEXTAREA_READONLY) ?
					READONLY_BG : BACKGROUND_COL,
			   	ta->style->color);
	}
}

/**
 * Key press handling for text areas.
 *
 * \param ta	The text area which got the keypress
 * \param key	The ucs4 character codepoint
 * \return     	true if the keypress is dealt with, false otherwise.
 */
bool textarea_keypress(struct text_area *ta, uint32_t key)
{
	char utf8[6];
	unsigned int caret, caret_init, length, l_len, b_off, b_len;
	int c_line, c_chars, line;
	bool redraw = false;
	bool readonly;

	caret_init = caret = textarea_get_caret(ta);
	line = ta->caret_pos.line;
	readonly = (ta->flags & TEXTAREA_READONLY ? true:false);
	
	
	if (!(key <= 0x001F || (0x007F <= key && key <= 0x009F))) {
		/* normal character insertion */		
		length = utf8_from_ucs4(key, utf8);
		utf8[length] = '\0';
		
		if (!textarea_insert_text(ta, caret, utf8))
			return false;
		caret++;
		redraw = true;

	} else switch (key) {
		case KEY_SELECT_ALL:
			caret = ta->text_utf8_len;
  			
 			ta->selection_start = 0;
			ta->selection_end = ta->text_utf8_len;
 			redraw = true;
 			break;
		case KEY_COPY_SELECTION:
			break;
		case KEY_DELETE_LEFT:
			if (readonly)
				break;
			if (ta->selection_start != -1) {
				if (!textarea_replace_text(ta,
				     		ta->selection_start,
						ta->selection_end, ""))
					return false;				
				ta->selection_start = ta->selection_end = -1;
				redraw = true;
			} else {
				if (caret) {
					if (!textarea_replace_text(ta,
					     		caret - 1,
							caret, ""))
						return false;
					caret--;
					redraw = true;
				}
			}
			break;
			break;
		case KEY_NL:
			if (readonly)
				break;
			if(!textarea_insert_text(ta, caret, "\n"))
				return false;
			caret++;
			ta->selection_start = ta->selection_end = -1;
			redraw = true;
			break;
		case KEY_CUT_LINE:
		case KEY_PASTE:
		case KEY_CUT_SELECTION:
			break;
		case KEY_ESCAPE:			
		case KEY_CLEAR_SELECTION:
			ta->selection_start = -1;
			ta->selection_end = -1;
			redraw = true;
			break;
		case KEY_LEFT:
			if (readonly)
				break;
			if (caret)
				caret--;
			if (ta->selection_start != -1) {
				ta->selection_start = ta->selection_end = -1;
				redraw = true;
			}
			break;
		case KEY_RIGHT:
			if (readonly)
				break;
			if (caret < ta->text_utf8_len)
				caret++;
			if (ta->selection_start != -1) {
				ta->selection_start = ta->selection_end = -1;
				redraw = true;
			}
			break;
		case KEY_PAGE_UP:
			if (readonly)
				break;
			if (ta->flags & TEXTAREA_MULTILINE) {
				/* +1 because one line is subtracted in
				   KEY_UP */
				line = ta->caret_pos.line - (ta->vis_height +
						ta->line_height - 1) /
						ta->line_height
						+ 1;
			}
			/* fall through */			
		case KEY_UP:
			if (readonly)
				break;
			if (ta->selection_start != -1) {
				ta->selection_start = ta->selection_end = -1;
				redraw = true;
			}
			if (ta->flags & TEXTAREA_MULTILINE) {
				line--;
				if (line < 0)
					line = 0;
				if (line == ta->caret_pos.line)
					break;
				
				b_off = ta->lines[line].b_start;
				b_len = ta->lines[line].b_length;
												
				c_line = ta->caret_pos.line;
				c_chars = ta->caret_pos.char_off;
				
				if (ta->text[b_off + b_len - 1] == ' '
						&& line < ta->line_count - 1)
					b_len--;
				
				l_len = utf8_bounded_length(&(ta->text[b_off]),
						b_len);
				
				
				ta->caret_pos.line = line;
				ta->caret_pos.char_off = min(l_len,
						(unsigned)
						ta->caret_pos.char_off);
				
				caret = textarea_get_caret(ta);
				
				ta->caret_pos.line = c_line;
				ta->caret_pos.char_off = c_chars;
			}
			break;
		case KEY_PAGE_DOWN:
			if (readonly)
				break;
			if (ta->flags & TEXTAREA_MULTILINE) {
				/* -1 because one line is added in KEY_DOWN */
				line = ta->caret_pos.line + (ta->vis_height +
						ta->line_height - 1) /
						ta->line_height
						- 1;
			}			
			/* fall through */
		case KEY_DOWN:
			if (readonly)
				break;
			if (ta->selection_start != -1) {
				ta->selection_start = ta->selection_end = -1;
				redraw = true;
			}
			if (ta->flags & TEXTAREA_MULTILINE) {
				line++;
				if (line > ta->line_count - 1)
					line = ta->line_count - 1;
				if (line == ta->caret_pos.line)
					break;
				
				b_off = ta->lines[line].b_start;
				b_len = ta->lines[line].b_length;
												
				c_line = ta->caret_pos.line;
				c_chars = ta->caret_pos.char_off;
				
				if (ta->text[b_off + b_len - 1] == ' '
						&& line < ta->line_count - 1)
					b_len--;
				
				l_len = utf8_bounded_length(&(ta->text[b_off]),
						b_len);
				
				
				ta->caret_pos.line = line;
				ta->caret_pos.char_off = min(l_len,
						(unsigned)
						ta->caret_pos.char_off);
				
				caret = textarea_get_caret(ta);
				
				ta->caret_pos.line = c_line;
				ta->caret_pos.char_off = c_chars;
			}
			break;
		case KEY_DELETE_RIGHT:
			if (readonly)
				break;
			if (ta->selection_start != -1) {
				if (!textarea_replace_text(ta,
				     		ta->selection_start,
						ta->selection_end, ""))
					return false;
					
				ta->selection_start = ta->selection_end = -1;
				redraw = true;
			} else {
				if (caret < ta->text_utf8_len) {
					if (!textarea_replace_text(ta, caret,
							caret + 1, ""))
						return false;
					redraw = true;
				}
			}
			break;			
		case KEY_LINE_START:
			if (readonly)
				break;
			caret -= ta->caret_pos.char_off;
			if (ta->selection_start != -1) {
				ta->selection_start = ta->selection_end = -1;
				redraw = true;
			}
			break;
		case KEY_LINE_END:
			if (readonly)
				break;
			
			caret = utf8_bounded_length(ta->text,
					ta->lines[ta->caret_pos.line].b_start +
					ta->lines[ta->caret_pos.line].b_length);
			if (ta->text[ta->lines[ta->caret_pos.line].b_start +
					ta->lines[ta->caret_pos.line].b_length
					- 1] == ' ')
				caret--;
			if (ta->selection_start != -1) {
				ta->selection_start = ta->selection_end = -1;
				redraw = true;
			}
			break;			
		case KEY_TEXT_START:
			if (readonly)
				break;
			caret = 0;
			if (ta->selection_start != -1) {
				ta->selection_start = ta->selection_end = -1;
				redraw = true;
			}
			break;
		case KEY_TEXT_END:
			if (readonly)
				break;
			caret = ta->text_utf8_len;
			if (ta->selection_start != -1) {
				ta->selection_start = ta->selection_end = -1;
				redraw = true;
			}
			break;
		case KEY_WORD_LEFT:
		case KEY_WORD_RIGHT:
			break;
		case KEY_DELETE_LINE_END:
			if (readonly)
				break;
			if (ta->selection_start != -1) {
				if (!textarea_replace_text(ta,
				     		ta->selection_start,
						ta->selection_end, ""))
					return false;
				ta->selection_start = ta->selection_end = -1;
			} else {
				b_off = ta->lines[ta->caret_pos.line].b_start;
				b_len = ta->lines[ta->caret_pos.line].b_length;
				l_len = utf8_bounded_length(&(ta->text[b_off]),
						b_len);
				if (!textarea_replace_text(ta, caret,
						caret + l_len, ""))
					return false;
			}
			redraw = true;
			break;
		case KEY_DELETE_LINE_START:
			if (readonly)
				break;
			if (ta->selection_start != -1) {
				if (!textarea_replace_text(ta,
				     		ta->selection_start,
						ta->selection_end, ""))
					return false;
				ta->selection_start = ta->selection_end = -1;
			} else {
				if (textarea_replace_text(ta,
						caret - ta->caret_pos.char_off,
      						caret,
						""))
					return false;
				caret -= ta->caret_pos.char_off;
			}
			redraw = true;			
			break;
		default:
			return false;
	}
	
	//TODO:redraw only the important part
	if (redraw) {
		ta->redraw_start_callback(ta->data);
		textarea_redraw(ta, ta->x, ta->y, ta->x + ta->vis_width,
				ta->y + ta->vis_height);
		ta->redraw_end_callback(ta->data);
	}
	
	if (caret != caret_init || redraw)
		return textarea_set_caret(ta, caret);
		
	return true;
}

/**
 * Scrolls a textarea to make the caret visible (doesn't perform a redraw)
 *
 * \param ta	The text area to be scrolled
 * \return 	true if textarea was scrolled false otherwise
 */
bool textarea_scroll_visible(struct text_area *ta)
{
	int x0, x1, y0, y1, x, y;
	int index, b_off;
	bool scrolled = false;
	
	if (ta->caret_pos.char_off == -1)
		return false;
	
	x0 = ta->x + MARGIN_LEFT;
	x1 = ta->x + ta->vis_width - MARGIN_RIGHT;
	y0 = ta->y;
	y1 = ta->y + ta->vis_height;
	
	index = textarea_get_caret(ta);

	/* find byte offset of caret position */
	for (b_off = 0; index-- > 0;
			b_off = utf8_next(ta->text, ta->text_len, b_off))
		; /* do nothing */

	nsfont.font_width(ta->style,
			ta->text + ta->lines[ta->caret_pos.line].b_start,
			b_off - ta->lines[ta->caret_pos.line].b_start,
			&x);
	
	/* top-left of caret */
	x += ta->x + MARGIN_LEFT - ta->scroll_x;
	y = ta->line_height * ta->caret_pos.line + ta->y - ta->scroll_y;
	
	/* check and change vertical scroll */
	if (y < y0) {
		ta->scroll_y -= y0 - y;
		scrolled = true;
	} else if (y + ta->line_height > y1) {
		ta->scroll_y += y + ta->line_height - y1;
		scrolled = true;
	}

	
	/* check and change horizontal scroll */
	if (x < x0) {
		ta->scroll_x -= x0 - x ;
		scrolled = true;
	} else if (x > x1 - 1) {
		ta->scroll_x += x - (x1 - 1);
		scrolled = true;
	}
	
	return scrolled;
}


/**
 * Handles all kinds of mouse action
 *
 * \param ta	Text area
 * \param mouse	the mouse state at action moment
 * \param x	X coordinate
 * \param y	Y coordinate
 * \return true if action was handled false otherwise
 */
bool textarea_mouse_action(struct text_area *ta, browser_mouse_state mouse,
		int x, int y)
{	
	int c_start, c_end;
	
	/* mouse button pressed above the text area, move caret */
	if (mouse & BROWSER_MOUSE_PRESS_1) {
		if (ta->selection_start != -1) {
			ta->selection_start = ta->selection_end = -1;
			ta->redraw_start_callback(ta->data);
			textarea_redraw(ta, ta->x, ta->y, ta->x + ta->vis_width,
					ta->y + ta->vis_height);
			ta->redraw_end_callback(ta->data);
		}
		if (!(ta->flags & TEXTAREA_READONLY))
			return textarea_set_caret_xy(ta, x, y);
	}
	else if (mouse & BROWSER_MOUSE_DRAG_1) {
		ta->drag_start_char = textarea_get_xy_offset(ta, x, y);
		if (!(ta->flags & TEXTAREA_READONLY))
			return textarea_set_caret(ta, -1);
	}
	else if (mouse & BROWSER_MOUSE_HOLDING_1) {
		c_start = ta->drag_start_char;
		c_end = textarea_get_xy_offset(ta, x, y);
		return textarea_select(ta, c_start, c_end);
		
	}
	
	return true;
}


/**
 * Handles the end of a drag operation
 *
 * \param ta	Text area
 * \param mouse	the mouse state at drag end moment
 * \param x	X coordinate
 * \param y	Y coordinate
 * \return true if drag end was handled false otherwise
 */
bool textarea_drag_end(struct text_area *ta, browser_mouse_state mouse,
		int x, int y)
{
	int c_end;

	c_end = textarea_get_xy_offset(ta, x, y);
	return textarea_select(ta, ta->drag_start_char, c_end);
}

/**
 * Selects a character range in the textarea and redraws it
 *
 * \param ta		Text area
 * \param c_start	First character (inclusive)
 * \param c_end		Last character (exclusive)
 * \return 		true on success false otherwise
 */
bool textarea_select(struct text_area *ta, int c_start, int c_end)
{
	int swap = -1;
	
	/* if start is after end they get swapped, start won't and end will
	   be selected this way */
	if (c_start > c_end) {
		swap = c_start;
		c_start = c_end;
		c_end = swap;
	}
	
	ta->selection_start = c_start;
	ta->selection_end = c_end;
	
	ta->redraw_start_callback(ta->data);
	textarea_redraw(ta, ta->x, ta->y, ta->x + ta->vis_width,
			ta->y + ta->vis_height);
	ta->redraw_end_callback(ta->data);

	if (!(ta->flags & TEXTAREA_READONLY)) {
		if (swap == -1)
			return textarea_set_caret(ta, c_end);
		else
			return textarea_set_caret(ta, c_start);
	}
	
	return true;
}


/**
 * Normalises any line endings within the text, replacing CRLF or CR with
 * LF as necessary. If the textarea is single line, then all linebreaks are
 * converted into spaces.
 *
 * \param ta		Text area
 * \param b_start	Byte offset to start at
 * \param b_len		Byte length to check
 */
void textarea_normalise_text(struct text_area *ta,
		unsigned int b_start, unsigned int b_len)
{
	bool multi = (ta->flags & TEXTAREA_MULTILINE) ? true:false;
	unsigned int index;
	
	/* Remove CR characters. If it's a CRLF pair delete it ot replace it
	 * with LF otherwise.
	 */
	for (index = 0; index < b_len; index++) {
		if (ta->text[b_start + index] == '\r') {
			if (b_start + index + 1 <= ta->text_len &&
					ta->text[b_start + index + 1] == '\n') {
				ta->text_len--;
				ta->text_utf8_len--;
				memmove(ta->text + b_start + index,
						ta->text + b_start + index + 1,
						ta->text_len - b_start - index);
			}
			else
				ta->text[b_start + index] = '\n';
		}
		/* Replace newlines with spaces if this is a single line
		 * textarea.
		 */
		if (!multi && (ta->text[b_start + index] == '\n'))
			ta->text[b_start + index] = ' ';
	}
	
}