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include/mupdf/fitz/story.h

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+// Copyright (C) 2004-2021 Artifex Software, Inc.
+//
+// This file is part of MuPDF.
+//
+// MuPDF is free software: you can redistribute it and/or modify it under the
+// terms of the GNU Affero General Public License as published by the Free
+// Software Foundation, either version 3 of the License, or (at your option)
+// any later version.
+//
+// MuPDF 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 Affero General Public License for more
+// details.
+//
+// You should have received a copy of the GNU Affero General Public License
+// along with MuPDF. If not, see <https://www.gnu.org/licenses/agpl-3.0.en.html>
+//
+// Alternative licensing terms are available from the licensor.
+// For commercial licensing, see <https://www.artifex.com/> or contact
+// Artifex Software, Inc., 39 Mesa Street, Suite 108A, San Francisco,
+// CA 94129, USA, for further information.
+
+#ifndef MUPDF_FITZ_STORY_H
+#define MUPDF_FITZ_STORY_H
+
+#include "mupdf/fitz/system.h"
+#include "mupdf/fitz/context.h"
+#include "mupdf/fitz/buffer.h"
+#include "mupdf/fitz/device.h"
+#include "mupdf/fitz/xml.h"
+#include "mupdf/fitz/archive.h"
+
+/*
+	This header file provides an API for laying out and placing styled
+	text on a page, or pages.
+
+	First a text story is created from some styled HTML.
+
+	Next, this story can be laid out into a given rectangle (possibly
+	retrying several times with updated rectangles as required).
+
+	Next, the laid out story can be drawn to a given device.
+
+	In the case where the text story cannot be fitted into the given
+	areas all at once, these two steps can be repeated multiple
+	times until the text story is completely consumed.
+
+	Finally, the text story can be dropped in the usual fashion.
+*/
+
+
+typedef struct fz_story fz_story;
+
+/*
+	Create a text story using styled html.
+
+	Passing a NULL buffer will be treated as an empty document.
+	Passing a NULL user_css will be treated as an empty CSS string.
+	A non-NULL dir will allow images etc to be loaded. The
+	story keeps its own reference, so the caller can drop its
+	reference after this call.
+*/
+fz_story *fz_new_story(fz_context *ctx, fz_buffer *buf, const char *user_css, float em, fz_archive *dir);
+
+/*
+	Retrieve the warnings given from parsing this story.
+
+	If there are warnings, this will be returned as a NULL terminated
+	C string. If there are no warnings, this will return NULL.
+
+	These warnings will not be complete until AFTER any DOM manipulations
+	have been completed.
+
+	This function does not need to be called, but once it has been
+	the DOM is no longer accessible, and any fz_xml pointer
+	retrieved from fz_story_docment is no longer valid.
+*/
+const char *fz_story_warnings(fz_context *ctx, fz_story *story);
+
+/*
+	Equivalent to fz_place_story_flags with flags being 0.
+*/
+int fz_place_story(fz_context *ctx, fz_story *story, fz_rect where, fz_rect *filled);
+
+/*
+	Place (or continue placing) a story into the supplied rectangle
+	'where', updating 'filled' with the actual area that was used.
+	Returns zero (FZ_PLACE_STORY_RETURN_ALL_FITTED) if all the
+	content fitted, non-zero if there is more to fit.
+
+	If the FZ_PLACE_STORY_FLAG_NO_OVERFLOW flag is set, then a
+	return code of FZ_PLACE_STORY_RETURN_OVERFLOW_WIDTH will be
+	returned when the next item (word) to be placed would not fit
+	in a rectangle of that given width.
+
+	Note, that filled may not be returned as a strict subset of
+	where, due to padding/margins at the bottom of pages, and
+	non-wrapping content extending to the right.
+
+	Subsequent calls will attempt to place the same section of story
+	again and again, until the placed story is drawn using fz_draw_story,
+	whereupon subsequent calls to fz_place_story will attempt to place
+	the unused remainder of the story.
+
+	After this function is called, the DOM is no longer accessible,
+	and any fz_xml pointer retrieved from fz_story_document is no
+	longer valid.
+
+	flags: Additional flags controlling layout. Pass 0 if none
+	required.
+*/
+int fz_place_story_flags(fz_context *ctx, fz_story *story, fz_rect where, fz_rect *filled, int flags);
+
+enum
+{
+	/* Avoid the usual HTML behaviour of overflowing the box horizontally
+	 * in some circumstances. We now abort the place in such cases and
+	 * return with */
+	FZ_PLACE_STORY_FLAG_NO_OVERFLOW = 1,
+
+	/* Specific return codes from fz_place_story_flags. Also
+	 * "non-zero" for 'more to fit'. */
+	FZ_PLACE_STORY_RETURN_ALL_FITTED = 0,
+	FZ_PLACE_STORY_RETURN_OVERFLOW_WIDTH = 2
+};
+
+/*
+	Draw the placed story to the given device.
+
+	This moves the point at which subsequent calls to fz_place_story
+	will restart placing to the end of what has just been output.
+*/
+void fz_draw_story(fz_context *ctx, fz_story *story, fz_device *dev, fz_matrix ctm);
+
+/*
+	Reset the position within the story at which the next layout call
+	will continue to the start of the story.
+*/
+void fz_reset_story(fz_context *ctx, fz_story *story);
+
+/*
+	Drop the html story.
+*/
+void fz_drop_story(fz_context *ctx, fz_story *story);
+
+/*
+	Get a borrowed reference to the DOM document pointer for this
+	story. Do not destroy this reference, it will be destroyed
+	when the story is laid out.
+
+	This only makes sense before the first placement of the story
+	or retrieval of the warnings. Once either of those things happen
+	the DOM representation is destroyed.
+*/
+fz_xml *fz_story_document(fz_context *ctx, fz_story *story);
+
+
+typedef struct
+{
+	/* The overall depth of this element in the box structure.
+	 * This can be used to compare the relative depths of different
+	 * elements, but shouldn't be relied upon not to change between
+	 * different versions of MuPDF. */
+	int depth;
+
+	/* The heading level of this element. 0 if not a header, or 1-6 for h1-h6. */
+	int heading;
+
+	/* The id for this element. */
+	const char *id;
+
+	/* The href for this element. */
+	const char *href;
+
+	/* The rectangle for this element. */
+	fz_rect rect;
+
+	/* The immediate text for this element. */
+	const char *text;
+
+	/* This indicates whether this opens and/or closes this element.
+	 *
+	 * As we traverse the tree we do a depth first search. In order for
+	 * the caller of fz_story_positions to know whether a given element
+	 * is inside another element, we therefore announce 'start' and 'stop'
+	 * for each element. For instance, with:
+	 *
+	 *   <div id="part1">
+	 *    <h1>Chapter 1</h1>...
+	 *    <h1>Chapter 2</h1>...
+	 *    ...
+	 *   </div>
+	 *   <div id="part2">
+	 *    <h1>Chapter 10</h1>...
+	 *    <h1>Chapter 11</h1>...
+	 *    ...
+	 *   </div>
+	 *
+	 * We would announce:
+	 *   + id='part1' (open)
+	 *   + header=1 "Chapter 1" (open/close)
+	 *   + header=1 "Chapter 2" (open/close)
+	 *   ...
+	 *   + id='part1' (close)
+	 *   + id='part2' (open)
+	 *   + header=1 "Chapter 10" (open/close)
+	 *   + header=1 "Chapter 11" (open/close)
+	 *   ...
+	 *   + id='part2' (close)
+	 *
+	 * If bit 0 is set, then this 'opens' the element.
+	 * If bit 1 is set, then this 'closes' the element.
+	 */
+	int open_close;
+
+	/* A count of the number of rectangles that the layout code has split the
+	 * story into so far. After the first layout, this will be 1. If a
+	 * layout is repeated, this number is not incremented. */
+	int rectangle_num;
+} fz_story_element_position;
+
+typedef void (fz_story_position_callback)(fz_context *ctx, void *arg, const fz_story_element_position *);
+
+/*
+	Enumerate the positions for key blocks in the story.
+
+	This will cause the supplied function to be called with details of each
+	element in the story that is either a header, or has an id.
+*/
+void fz_story_positions(fz_context *ctx, fz_story *story, fz_story_position_callback *cb, void *arg);
+
+#endif