netsurf/desktop/selection.c

/*
 * Copyright 2005 Adrian Lees <adrianl@users.sourceforge.net>
 * Copyright 2008 Michael Drake <tlsa@netsurf-browser.org>
 *
 * 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
 * implementation of text selection within browser windows.
 */

#include <assert.h>
#include <stdio.h>
#include <stdlib.h>
#include <stdbool.h>
#include <string.h>
#include <dom/dom.h>

#include "utils/log.h"
#include "utils/utf8.h"
#include "utils/utils.h"
#include "netsurf/form.h"
#include "html/box.h"
#include "html/box_inspect.h"
#include "html/private.h"
#include "html/font.h"
#include "text/textplain.h"
#include "netsurf/browser_window.h"

#include "netsurf/mouse.h"
#include "desktop/browser_private.h"
#include "netsurf/plotters.h"
#include "desktop/save_text.h"
#include "desktop/selection.h"
#include "netsurf/clipboard.h"
#include "netsurf/window.h"
#include "desktop/gui_internal.h"

/**
 * Text selection works by labelling each node in the box tree with its
 * start index in the textual representation of the tree's content.
 */

#define SPACE_LEN(b) ((b->space == 0) ? 0 : 1)


struct rdw_info {
	bool inited;
	struct rect r;
};

struct selection_string {
	char *buffer;
	size_t buffer_len;
	size_t length;

	int n_styles;
	nsclipboard_styles *styles;
};


typedef bool (*seln_traverse_handler)(const char *text,
				      size_t length,
				      struct box *box,
				      const nscss_len_ctx *len_ctx,
				      void *handle,
				      const char *whitespace_text,
				      size_t whitespace_length);


/**
 * Label each text box in the given box subtree with its position
 * in a textual representation of the content.
 *
 * \param box The box at root of subtree
 * \param idx current position within textual representation
 * \return updated position
 */
static unsigned selection_label_subtree(struct box *box, unsigned idx)
{
	struct box *child = box->children;

	box->byte_offset = idx;

	if (box->text) {
		idx += box->length + SPACE_LEN(box);
	}

	while (child) {
		if (child->list_marker) {
			idx = selection_label_subtree(child->list_marker, idx);
		}

		idx = selection_label_subtree(child, idx);
		child = child->next;
	}

	return idx;
}


/**
 * Tests whether a text box lies partially within the given range of
 * byte offsets, returning the start and end indexes of the bytes
 * that are enclosed.
 *
 * \param box box to be tested
 * \param start_idx byte offset of start of range
 * \param end_idx byte offset of end of range
 * \param start_offset receives the start offset of the selected part
 * \param end_offset receives the end offset of the selected part
 * \return true iff the range encloses at least part of the box
 */
static bool
selected_part(struct box *box,
	      unsigned start_idx,
	      unsigned end_idx,
	      unsigned *start_offset,
	      unsigned *end_offset)
{
	size_t box_length = box->length + SPACE_LEN(box);

	if (box_length > 0) {
		if ((box->byte_offset >= start_idx) &&
		    (box->byte_offset + box_length <= end_idx)) {

			/* fully enclosed */
			*start_offset = 0;
			*end_offset = box_length;
			return true;
		} else if ((box->byte_offset + box_length > start_idx) &&
			   (box->byte_offset < end_idx)) {
			/* partly enclosed */
			int offset = 0;
			int len;

			if (box->byte_offset < start_idx) {
				offset = start_idx - box->byte_offset;
			}

			len = box_length - offset;

			if (box->byte_offset + box_length > end_idx) {
				len = end_idx - (box->byte_offset + offset);
			}

			*start_offset = offset;
			*end_offset = offset + len;

			return true;
		}
	}
	return false;
}


/**
 * Traverse the given box subtree, calling the handler function (with
 * its handle) for all boxes that lie (partially) within the given
 * range
 *
 * \param box        box subtree
 * \param len_ctx    Length conversion context.
 * \param start_idx  start of range within textual representation (bytes)
 * \param end_idx    end of range
 * \param handler    handler function to call
 * \param handle     handle to pass
 * \param before     type of whitespace to place before next encountered text
 * \param first      whether this is the first box with text
 * \param do_marker  whether deal enter any marker box
 * \return false iff traversal abandoned part-way through
 */
static bool
traverse_tree(struct box *box,
	      const nscss_len_ctx *len_ctx,
	      unsigned start_idx,
	      unsigned end_idx,
	      seln_traverse_handler handler,
	      void *handle,
	      save_text_whitespace *before,
	      bool *first,
	      bool do_marker)
{
	struct box *child;
	const char *whitespace_text = "";
	size_t whitespace_length = 0;

	assert(box);

	/* If selection starts inside marker */
	if (box->parent &&
	    box->parent->list_marker == box &&
	    !do_marker) {
		/* set box to main list element */
		box = box->parent;
	}

	/* If box has a list marker */
	if (box->list_marker) {
		/* do the marker box before continuing with the rest of the
		 * list element */
		if (!traverse_tree(box->list_marker,
				   len_ctx,
				   start_idx,
				   end_idx,
				   handler,
				   handle,
				   before,
				   first,
				   true)) {
			return false;
		}
	}

	/* we can prune this subtree, it's after the selection */
	if (box->byte_offset >= end_idx) {
		return true;
	}

	/* read before calling the handler in case it modifies the tree */
	child = box->children;

	/* If nicely formatted output of the selected text is required, work
	 * out what whitespace should be placed before the next bit of text */
	if (before) {
		save_text_solve_whitespace(box,
					   first,
					   before,
					   &whitespace_text,
					   &whitespace_length);
	} else {
		whitespace_text = NULL;
	}

	if ((box->type != BOX_BR) &&
	    !((box->type == BOX_FLOAT_LEFT ||
	       box->type == BOX_FLOAT_RIGHT) &&
	      !box->text)) {
		unsigned start_offset;
		unsigned end_offset;

		if (selected_part(box,
				  start_idx,
				  end_idx,
				  &start_offset,
				  &end_offset)) {
			if (!handler(box->text + start_offset,
				     min(box->length, end_offset) - start_offset,
				     box,
				     len_ctx,
				     handle,
				     whitespace_text,
				     whitespace_length)) {
				return false;
			}
			if (before) {
				*first = false;
				*before = WHITESPACE_NONE;
			}
		}
	}

	/* find the first child that could lie partially within the selection;
	 * this is important at the top-levels of the tree for pruning subtrees
	 * that lie entirely before the selection */

	if (child) {
		struct box *next = child->next;

		while (next && next->byte_offset < start_idx) {
			child = next;
			next = child->next;
		}

		while (child) {
			/* read before calling the handler in case it modifies
			 * the tree */
			struct box *next = child->next;

			if (!traverse_tree(child,
					   len_ctx,
					   start_idx,
					   end_idx,
					   handler,
					   handle,
					   before,
					   first,
					   false)) {
				return false;
			}

			child = next;
		}
	}

	return true;
}


/**
 * Selection traversal handler for redrawing the screen when the selection
 * has been altered.
 *
 * \param  text		pointer to text string
 * \param  length	length of text to be appended (bytes)
 * \param  box		pointer to text box being (partially) added
 * \param  handle	unused handle, we don't need one
 * \param  whitespace_text    whitespace to place before text for formatting
 *                            may be NULL
 * \param  whitespace_length  length of whitespace_text
 * \return true iff successful and traversal should continue
 */
static bool
redraw_handler(const char *text,
	       size_t length,
	       struct box *box,
	       const nscss_len_ctx *len_ctx,
	       void *handle,
	       const char *whitespace_text,
	       size_t whitespace_length)
{
	struct rdw_info *r = (struct rdw_info*)handle;
	int width, height;
	int x, y;

	if (!box) {
		return true;
	}

	/* \todo - it should be possible to reduce the redrawn area by
	 * considering the 'text', 'length' and 'space' parameters */
	box_coords(box, &x, &y);

	width = box->padding[LEFT] + box->width + box->padding[RIGHT];
	height = box->padding[TOP] + box->height + box->padding[BOTTOM];

	if ((box->type == BOX_TEXT) &&
	    (box->space != 0)) {
		width += box->space;
	}

	if (r->inited) {
		if (x < r->r.x0) r->r.x0 = x;
		if (y < r->r.y0) r->r.y0 = y;
		if (x + width > r->r.x1) r->r.x1 = x + width;
		if (y + height > r->r.y1) r->r.y1 = y + height;
	} else {
		r->inited = true;
		r->r.x0 = x;
		r->r.y0 = y;
		r->r.x1 = x + width;
		r->r.y1 = y + height;
	}

	return true;
}


/**
 * Redraws the given range of text.
 *
 * \param s selection object
 * \param start_idx start offset (bytes) within the textual representation
 * \param end_idx end offset (bytes) within the textual representation
 */
static void
selection_redraw(struct selection *s, unsigned start_idx, unsigned end_idx)
{
	struct rdw_info rdw;

	assert(end_idx >= start_idx);
	rdw.inited = false;

	if (s->root) {
		if (!traverse_tree(s->root,
				   &s->len_ctx,
				   start_idx,
				   end_idx,
				   redraw_handler,
				   &rdw,
				   NULL,
				   NULL,
				   false))
			return;
	} else {
		if ((s->is_html == false) &&
		    (end_idx > start_idx)) {
			textplain_coords_from_range(s->c,
						    start_idx,
						    end_idx,
						    &rdw.r);
			rdw.inited = true;
		}
	}

	if (rdw.inited) {
		content__request_redraw(s->c,
					rdw.r.x0,
					rdw.r.y0,
					rdw.r.x1 - rdw.r.x0,
					rdw.r.y1 - rdw.r.y0);
	}
}


/**
 * Set the start position of the current selection, updating the screen.
 *
 * \param s selection object
 * \param offset byte offset within textual representation
 */
static void selection_set_start(struct selection *s, unsigned offset)
{
	bool was_defined;
	unsigned old_start;

	old_start = s->start_idx;
	s->start_idx = offset;

	was_defined = s->defined;
	s->defined = (s->start_idx < s->end_idx);

	if (was_defined) {
		if (offset < old_start) {
			selection_redraw(s, s->start_idx, old_start);
		} else {
			selection_redraw(s, old_start, s->start_idx);
		}
	} else if (s->defined) {
		selection_redraw(s, s->start_idx, s->end_idx);
	}
}


/**
 * Set the end position of the current selection, updating the screen.
 *
 * \param s selection object
 * \param offset byte offset within textual representation
 */
static void selection_set_end(struct selection *s, unsigned offset)
{
	bool was_defined;
	unsigned old_end;

	old_end = s->end_idx;
	s->end_idx = offset;

	was_defined = s->defined;
	s->defined = (s->start_idx < s->end_idx);

	if (was_defined) {
		if (offset < old_end) {
			selection_redraw(s, s->end_idx, old_end);
		} else {
			selection_redraw(s, old_end, s->end_idx);
		}
	} else if (s->defined) {
		selection_redraw(s, s->start_idx, s->end_idx);
	}
}


/**
 * Traverse the current selection, calling the handler function (with its
 * handle) for all boxes that lie (partially) within the given range
 *
 * \param s The selection context.
 * \param handler handler function to call
 * \param handle  handle to pass
 * \return false iff traversal abandoned part-way through
 */
static bool
selection_traverse(struct selection *s,
		   seln_traverse_handler handler,
		   void *handle)
{
	save_text_whitespace before = WHITESPACE_NONE;
	bool first = true;
	const char *text;
	size_t length;

	if (!s->defined) {
		return true;	/* easy case, nothing to do */
	}

	if (s->root) {
		/* HTML */
		return traverse_tree(s->root, &s->len_ctx,
				     s->start_idx, s->end_idx,
				     handler, handle,
				     &before, &first, false);
	}

	/* Text */
	text = textplain_get_raw_data(s->c, s->start_idx, s->end_idx, &length);

	if (text &&
	    !handler(text, length, NULL, NULL, handle, NULL, 0)) {
		return false;
	}

	return true;
}


/**
 * Append text to selection string.
 *
 * \param text text to be added
 * \param length length of text in bytes
 * \param space indicates whether a trailing space should be appended
 * \param style The font style to use.
 * \param sel_string string to append to, may be resized
 * \return true iff successful
 */
static bool
selection_string_append(const char *text,
			size_t length,
			bool space,
			plot_font_style_t *style,
			struct selection_string *sel_string)
{
	size_t new_length = sel_string->length + length + (space ? 1 : 0) + 1;

	if (style != NULL) {
		/* Add text run style */
		nsclipboard_styles *new_styles;

		if (sel_string->n_styles == 0) {
			assert(sel_string->length == 0);
		}

		new_styles = realloc(sel_string->styles,
				     (sel_string->n_styles + 1) *
				     sizeof(nsclipboard_styles));
		if (new_styles == NULL) {
			return false;
		}

		sel_string->styles = new_styles;

		sel_string->styles[sel_string->n_styles].style = *style;
		sel_string->styles[sel_string->n_styles].start =
			sel_string->length;

		sel_string->n_styles++;
	}

	if (new_length > sel_string->buffer_len) {
		/* Need to extend buffer */
		size_t new_alloc = new_length + (new_length / 4);
		char *new_buff;

		new_buff = realloc(sel_string->buffer, new_alloc);
		if (new_buff == NULL) {
			return false;
		}

		sel_string->buffer = new_buff;
		sel_string->buffer_len = new_alloc;
	}

	/* Copy text onto end of existing text in buffer */
	memcpy(sel_string->buffer + sel_string->length, text, length);
	sel_string->length += length;

	if (space) {
		sel_string->buffer[sel_string->length++] = ' ';
	}

	/* Ensure NULL termination */
	sel_string->buffer[sel_string->length] = '\0';

	return true;
}


/**
 * Selection traversal routine for appending text to a string
 *
 * \param  text         pointer to text being added, or NULL for newline
 * \param  length       length of text to be appended (bytes)
 * \param  box          pointer to text box, or NULL if from textplain
 * \param  len_ctx      Length conversion context
 * \param  handle       selection string to append to
 * \param  whitespace_text    whitespace to place before text for formatting
 *                            may be NULL
 * \param  whitespace_length  length of whitespace_text
 * \return true iff successful and traversal should continue
 */
static bool
selection_copy_handler(const char *text,
		       size_t length,
		       struct box *box,
		       const nscss_len_ctx *len_ctx,
		       void *handle,
		       const char *whitespace_text,
		       size_t whitespace_length)
{
	bool add_space = false;
	plot_font_style_t style;
	plot_font_style_t *pstyle = NULL;

	/* add any whitespace which precedes the text from this box */
	if (whitespace_text != NULL &&
	    whitespace_length > 0) {
		if (!selection_string_append(whitespace_text,
					     whitespace_length,
					     false,
					     pstyle,
					     handle)) {
			return false;
		}
	}

	if (box != NULL) {
		/* HTML */
		add_space = (box->space != 0);

		if (box->style != NULL) {
			/* Override default font style */
			font_plot_style_from_css(len_ctx, box->style, &style);
			pstyle = &style;
		} else {
			/* If there's no style, there must be no text */
			assert(box->text == NULL);
		}
	}

	/* add the text from this box */
	if (!selection_string_append(text, length, add_space, pstyle, handle)) {
		return false;
	}

	return true;
}


/* exported interface documented in desktop/selection.h */
struct selection *selection_create(struct content *c, bool is_html)
{
	struct selection *s;
	s = calloc(1, sizeof(struct selection));
	if (s) {
		selection_prepare(s, c, is_html);
	}

	return s;
}


/* exported interface documented in desktop/selection.h */
void selection_prepare(struct selection *s, struct content *c, bool is_html)
{
	if (s) {
		s->c = c;
		s->is_html = is_html;
		s->root = NULL;
		s->drag_state = DRAG_NONE;
		s->max_idx = 0;
		selection_clear(s, false);
	}
}


/* exported interface documented in desktop/selection.h */
void selection_destroy(struct selection *s)
{
	if (s == NULL) {
		return;
	}

	selection_clear(s, true);
	free(s);
}


/* exported interface documented in desktop/selection.h */
void selection_reinit(struct selection *s, struct box *root)
{
	unsigned root_idx;

	assert(s);

	root_idx = 0;

	s->root = root;
	if (root) {
		s->max_idx = selection_label_subtree(root, root_idx);
	} else {
		if (s->is_html == false) {
			s->max_idx = textplain_size(s->c);
		} else {
			s->max_idx = 0;
		}
	}

	if (s->defined) {
		if (s->end_idx > s->max_idx) {
			s->end_idx = s->max_idx;
		}
		if (s->start_idx > s->max_idx) {
			s->start_idx = s->max_idx;
		}
		s->defined = (s->end_idx > s->start_idx);
	}
}


/* exported interface documented in desktop/selection.h */
void
selection_init(struct selection *s,
	       struct box *root,
	       const nscss_len_ctx *len_ctx)
{
	if (s->defined) {
		selection_clear(s, true);
	}

	s->defined = false;
	s->start_idx = 0;
	s->end_idx = 0;
	s->drag_state = DRAG_NONE;
	if (len_ctx != NULL) {
		s->len_ctx = *len_ctx;
	} else {
		s->len_ctx.vw = 0;
		s->len_ctx.vh = 0;
		s->len_ctx.root_style = NULL;
	}

	selection_reinit(s, root);
}


/* exported interface documented in desktop/selection.h */
bool
selection_click(struct selection *s,
		struct browser_window *top,
		browser_mouse_state mouse,
		unsigned idx)
{
	browser_mouse_state modkeys;
	int pos = -1;  /* 0 = inside selection, 1 = after it */

	modkeys = (mouse & (BROWSER_MOUSE_MOD_1 | BROWSER_MOUSE_MOD_2));

	top = browser_window_get_root(top);

	if (selection_defined(s)) {
		if (idx > s->start_idx) {
			if (idx <= s->end_idx) {
				pos = 0;
			} else {
				pos = 1;
			}
		}
	}

	if (!pos &&
	    ((mouse & BROWSER_MOUSE_DRAG_1) ||
	     (modkeys && (mouse & BROWSER_MOUSE_DRAG_2)))) {
		/* drag-saving selection */
		char *sel = selection_get_copy(s);
		guit->window->drag_save_selection(top->window, sel);
		free(sel);
	} else if (!modkeys) {
		if (pos && (mouse & BROWSER_MOUSE_PRESS_1)) {
			/* Clear the selection if mouse is pressed
			 * outside the selection, Otherwise clear on
			 * release (to allow for drags)
			 */

			selection_clear(s, true);

		} else if (mouse & BROWSER_MOUSE_DRAG_1) {
			/* start new selection drag */

			selection_clear(s, true);

			selection_set_start(s, idx);
			selection_set_end(s, idx);

			s->drag_state = DRAG_END;

			guit->window->event(top->window,
					    GW_EVENT_START_SELECTION);

		} else if (mouse & BROWSER_MOUSE_DRAG_2) {

			/* adjust selection, but only if there is one */
			if (!selection_defined(s)) {
				return false;	/* ignore Adjust drags */
			}

			if (pos >= 0) {
				selection_set_end(s, idx);

				s->drag_state = DRAG_END;
			} else {
				selection_set_start(s, idx);

				s->drag_state = DRAG_START;
			}

			guit->window->event(top->window,
					    GW_EVENT_START_SELECTION);

		} else if (mouse & BROWSER_MOUSE_CLICK_2) {

			/* ignore Adjust clicks when there's no selection */
			if (!selection_defined(s)) {
				return false;
			}

			if (pos >= 0) {
				selection_set_end(s, idx);
			} else {
				selection_set_start(s, idx);
			}
			s->drag_state = DRAG_NONE;

		} else {
			return false;
		}

	} else {
		/* not our problem */
		return false;
	}

	/* this mouse click is selection-related */
	return true;
}


/* exported interface documented in desktop/selection.h */
void
selection_track(struct selection *s, browser_mouse_state mouse, unsigned idx)
{
	if (!mouse) {
		s->drag_state = DRAG_NONE;
	}

	switch (s->drag_state) {

	case DRAG_START:
		if (idx > s->end_idx) {
			unsigned old_end = s->end_idx;
			selection_set_end(s, idx);
			selection_set_start(s, old_end);
			s->drag_state = DRAG_END;
		} else {
			selection_set_start(s, idx);
		}
		break;

	case DRAG_END:
		if (idx < s->start_idx) {
			unsigned old_start = s->start_idx;
			selection_set_start(s, idx);
			selection_set_end(s, old_start);
			s->drag_state = DRAG_START;
		} else {
			selection_set_end(s, idx);
		}
		break;

	default:
		break;
	}
}


/* exported interface documented in desktop/selection.h */
char *selection_get_copy(struct selection *s)
{
	struct selection_string sel_string = {
		.buffer = NULL,
		.buffer_len = 0,
		.length = 0,

		.n_styles = 0,
		.styles = NULL
	};

	if (s == NULL || !s->defined)
		return NULL;

	if (!selection_traverse(s, selection_copy_handler, &sel_string)) {
		free(sel_string.buffer);
		free(sel_string.styles);
		return NULL;
	}

	free(sel_string.styles);

	return sel_string.buffer;
}


/* exported interface documented in desktop/selection.h */
bool selection_copy_to_clipboard(struct selection *s)
{
	struct selection_string sel_string = {
		.buffer = NULL,
		.buffer_len = 0,
		.length = 0,

		.n_styles = 0,
		.styles = NULL
	};

	if (s == NULL || !s->defined) {
		return false;
	}

	if (!selection_traverse(s, selection_copy_handler, &sel_string)) {
		free(sel_string.buffer);
		free(sel_string.styles);
		return false;
	}

	guit->clipboard->set(sel_string.buffer,
			     sel_string.length,
			     sel_string.styles,
			     sel_string.n_styles);

	free(sel_string.buffer);
	free(sel_string.styles);

	return true;
}


/* exported interface documented in desktop/selection.h */
void selection_clear(struct selection *s, bool redraw)
{
	int old_start, old_end;
	bool was_defined;

	assert(s);

	was_defined = s->defined;
	old_start = s->start_idx;
	old_end = s->end_idx;

	s->defined = false;
	s->start_idx = 0;
	s->end_idx = 0;

	if (redraw && was_defined) {
		selection_redraw(s, old_start, old_end);
	}
}


/* exported interface documented in desktop/selection.h */
void selection_select_all(struct selection *s)
{
	assert(s);
	s->defined = true;

	selection_set_start(s, 0);
	selection_set_end(s, s->max_idx);
}


/* exported interface documented in desktop/selection.h */
void selection_set_position(struct selection *s, unsigned start, unsigned end)
{
	selection_set_start(s, start);
	selection_set_end(s, end);
}


/* exported interface documented in desktop/selection.h */
bool
selection_highlighted(const struct selection *s,
		      unsigned start,
		      unsigned end,
		      unsigned *start_idx,
		      unsigned *end_idx)
{
	/* caller should have checked first for efficiency */
	assert(s);
	assert(s->defined);

	if ((end <= s->start_idx) ||
	    (start >= s->end_idx)) {
		return false;
	}

	*start_idx = (s->start_idx >= start) ? (s->start_idx - start) : 0;
	*end_idx = min(end, s->end_idx) - start;

	return true;
}