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diff --git a/content/handlers/html/textselection.c b/content/handlers/html/textselection.c
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+/*
+ * Copyright 2020 Vincent Sanders <vince@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 for a HTML content.
+ */
+
+#include <stdlib.h>
+
+#include "utils/errors.h"
+#include "utils/utils.h"
+#include "netsurf/types.h"
+#include "netsurf/plot_style.h"
+#include "desktop/selection.h"
+#include "desktop/save_text.h"
+
+#include "html/private.h"
+#include "html/box.h"
+#include "html/box_inspect.h"
+#include "html/font.h"
+#include "html/textselection.h"
+
+#define SPACE_LEN(b) ((b->space == 0) ? 0 : 1)
+
+struct rdw_info {
+ bool inited;
+ struct rect r;
+};
+
+
+/**
+ * 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 adding the boxes inside the
+ * selection to the coordinate range.
+ *
+ * \param box box subtree
+ * \param start_idx start of range within textual representation (bytes)
+ * \param end_idx end of range
+ * \param rdwi redraw range to fill in
+ * \param do_marker whether deal enter any marker box
+ * \return NSERROR_OK on success else error code
+ */
+static nserror
+coords_from_range(struct box *box,
+ unsigned start_idx,
+ unsigned end_idx,
+ struct rdw_info *rdwi,
+ bool do_marker)
+{
+ struct box *child;
+ nserror res;
+
+ 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 */
+ res = coords_from_range(box->list_marker,
+ start_idx,
+ end_idx,
+ rdwi,
+ true);
+ if (res != NSERROR_OK) {
+ return res;
+ }
+ }
+
+ /* we can prune this subtree, it's after the selection */
+ if (box->byte_offset >= end_idx) {
+ return NSERROR_OK;
+ }
+
+ /* read before calling the handler in case it modifies the tree */
+ child = box->children;
+
+ if ((box->type != BOX_BR) &&
+ !((box->type == BOX_FLOAT_LEFT ||
+ box->type == BOX_FLOAT_RIGHT) &&
+ !box->text)) {
+ unsigned start_off;
+ unsigned end_off;
+
+ if (selected_part(box, start_idx, end_idx, &start_off, &end_off)) {
+ int width, height;
+ int x, y;
+
+ /**
+ * \todo it should be possible to reduce the redrawn
+ * area using the offsets
+ */
+ 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 (rdwi->inited) {
+ if (x < rdwi->r.x0) {
+ rdwi->r.x0 = x;
+ }
+ if (y < rdwi->r.y0) {
+ rdwi->r.y0 = y;
+ }
+ if (x + width > rdwi->r.x1) {
+ rdwi->r.x1 = x + width;
+ }
+ if (y + height > rdwi->r.y1) {
+ rdwi->r.y1 = y + height;
+ }
+ } else {
+ rdwi->inited = true;
+ rdwi->r.x0 = x;
+ rdwi->r.y0 = y;
+ rdwi->r.x1 = x + width;
+ rdwi->r.y1 = y + height;
+ }
+ }
+ }
+
+ /* 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;
+
+ res = coords_from_range(child,
+ start_idx,
+ end_idx,
+ rdwi,
+ false);
+ if (res != NSERROR_OK) {
+ return res;
+ }
+
+ child = next;
+ }
+ }
+
+ return NSERROR_OK;
+}
+
+
+/**
+ * Append the contents of a box to a selection along with style information
+ *
+ * \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 unit_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 NSERROR_OK iff successful and traversal should continue else error code
+ */
+static nserror
+selection_copy_box(const char *text,
+ size_t length,
+ struct box *box,
+ const css_unit_ctx *unit_len_ctx,
+ struct selection_string *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 NSERROR_NOMEM;
+ }
+ }
+
+ if (box != NULL) {
+ /* HTML */
+ add_space = (box->space != 0);
+
+ if (box->style != NULL) {
+ /* Override default font style */
+ font_plot_style_from_css(unit_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 NSERROR_NOMEM;
+ }
+
+ return NSERROR_OK;
+}
+
+
+/**
+ * Traverse the given box subtree, calling selection copy for all
+ * boxes that lie (partially) within the given range
+ *
+ * \param box box subtree
+ * \param unit_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 NSERROR_OK on sucess else error code
+ */
+static nserror
+selection_copy(struct box *box,
+ const css_unit_ctx *unit_len_ctx,
+ unsigned start_idx,
+ unsigned end_idx,
+ struct selection_string *selstr,
+ save_text_whitespace *before,
+ bool *first,
+ bool do_marker)
+{
+ nserror res;
+ 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 */
+ res = selection_copy(box->list_marker,
+ unit_len_ctx,
+ start_idx,
+ end_idx,
+ selstr,
+ before,
+ first,
+ true);
+ if (res != NSERROR_OK) {
+ return res;
+ }
+ }
+
+ /* we can prune this subtree, it's after the selection */
+ if (box->byte_offset >= end_idx) {
+ return NSERROR_OK;
+ }
+
+ /* 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_off;
+ unsigned end_off;
+
+ if (selected_part(box, start_idx, end_idx, &start_off, &end_off)) {
+ res = selection_copy_box(box->text + start_off,
+ min(box->length, end_off) - start_off,
+ box,
+ unit_len_ctx,
+ selstr,
+ whitespace_text,
+ whitespace_length);
+ if (res != NSERROR_OK) {
+ return res;
+ }
+ 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;
+
+ res = selection_copy(child,
+ unit_len_ctx,
+ start_idx,
+ end_idx,
+ selstr,
+ before,
+ first,
+ false);
+ if (res != NSERROR_OK) {
+ return res;
+ }
+
+ child = next;
+ }
+ }
+
+ return NSERROR_OK;
+}
+
+
+/**
+ * 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;
+
+ assert(box != NULL);
+
+ 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;
+}
+
+
+/* exported interface documented in html/textselection.h */
+nserror
+html_textselection_redraw(struct content *c,
+ unsigned start_idx,
+ unsigned end_idx)
+{
+ nserror res;
+ html_content *html = (html_content *)c;
+ struct rdw_info rdw;
+
+ if (html->layout == NULL) {
+ return NSERROR_INVALID;
+ }
+
+ rdw.inited = false;
+
+ res = coords_from_range(html->layout, start_idx, end_idx, &rdw, false);
+ if (res != NSERROR_OK) {
+ return res;
+ }
+
+ if (rdw.inited) {
+ content__request_redraw(c,
+ rdw.r.x0,
+ rdw.r.y0,
+ rdw.r.x1 - rdw.r.x0,
+ rdw.r.y1 - rdw.r.y0);
+ }
+
+ return NSERROR_OK;
+}
+
+
+/* exported interface documented in html/textselection.h */
+nserror
+html_textselection_copy(struct content *c,
+ unsigned start_idx,
+ unsigned end_idx,
+ struct selection_string *selstr)
+{
+ html_content *html = (html_content *)c;
+ save_text_whitespace before = WHITESPACE_NONE;
+ bool first = true;
+
+ if (html->layout == NULL) {
+ return NSERROR_INVALID;
+ }
+
+ return selection_copy(html->layout,
+ &html->unit_len_ctx,
+ start_idx,
+ end_idx,
+ selstr,
+ &before,
+ &first,
+ false);
+}
+
+
+/* exported interface documented in html/textselection.h */
+nserror
+html_textselection_get_end(struct content *c, unsigned *end_idx)
+{
+ html_content *html = (html_content *)c;
+ unsigned root_idx;
+
+ if (html->layout == NULL) {
+ return NSERROR_INVALID;
+ }
+
+ root_idx = 0;
+
+ *end_idx = selection_label_subtree(html->layout, root_idx);
+
+ return NSERROR_OK;
+}
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