/pango/pango-layout.c

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/* Pango
 * pango-layout.c: High-level layout driver
 *
 * Copyright (C) 2000, 2001, 2006 Red Hat Software
 *
 * This library is free software; you can redistribute it and/or
 * modify it under the terms of the GNU Library General Public
 * License as published by the Free Software Foundation; either
 * version 2 of the License, or (at your option) any later version.
 *
 * This library 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
 * Library General Public License for more details.
 *
 * You should have received a copy of the GNU Library General Public
 * License along with this library; if not, write to the
 * Free Software Foundation, Inc., 59 Temple Place - Suite 330,
 * Boston, MA 02111-1307, USA.
 */

/**
 * SECTION:layout
 * @short_description:High-level layout driver objects
 * @title:Layout Objects
 *
 * While complete access to the layout capabilities of Pango is provided
 * using the detailed interfaces for itemization and shaping, using
 * that functionality directly involves writing a fairly large amount
 * of code. The objects and functions in this section provide a
 * high-level driver for formatting entire paragraphs of text
 * at once.
 */

/**
 * PangoLayout:
 *
 * The #PangoLayout structure represents an entire paragraph
 * of text. It is initialized with a #PangoContext, UTF-8 string
 * and set of attributes for that string. Once that is done, the
 * set of formatted lines can be extracted from the object,
 * the layout can be rendered, and conversion between logical
 * character positions within the layout's text, and the physical
 * position of the resulting glyphs can be made.
 *
 * There are also a number of parameters to adjust the formatting
 * of a #PangoLayout, which are illustrated in <xref linkend="parameters"/>.
 * It is possible, as well, to ignore the 2-D setup, and simply
 * treat the results of a #PangoLayout as a list of lines.
 *
 * <figure id="parameters">
 * <title>Adjustable parameters for a PangoLayout</title>
 * <graphic fileref="layout.gif" format="GIF"></graphic>
 * </figure>
 *
 * The #PangoLayout structure is opaque, and has no user-visible
 * fields.
 */

/**
 * PangoLayoutIter:
 *
 * A #PangoLayoutIter structure can be used to
 * iterate over the visual extents of a #PangoLayout.
 *
 * The #PangoLayoutIter structure is opaque, and
 * has no user-visible fields.
 */

#include "config.h"
#include "pango-glyph.h"		/* For pango_shape() */
#include "pango-break.h"
#include "pango-item.h"
#include "pango-engine.h"
#include "pango-impl-utils.h"
#include "pango-glyph-item.h"
#include <string.h>

#include "pango-layout-private.h"


typedef struct _ItemProperties ItemProperties;
typedef struct _ParaBreakState ParaBreakState;

struct _ItemProperties
{
  PangoUnderline  uline;
  gboolean        strikethrough;
  gint            rise;
  gint            letter_spacing;
  gboolean        shape_set;
  PangoRectangle *shape_ink_rect;
  PangoRectangle *shape_logical_rect;
};

typedef struct _PangoLayoutLinePrivate PangoLayoutLinePrivate;

struct _PangoLayoutLinePrivate
{
  PangoLayoutLine line;
  guint ref_count;

  /* Extents cache status:
   *
   * LEAKED means that the user has access to this line structure or a
   * run included in this line, and so can change the glyphs/glyph-widths.
   * If this is true, extents caching will be disabled.
   */
  enum {
    NOT_CACHED,
    CACHED,
    LEAKED
  } cache_status;
  PangoRectangle ink_rect;
  PangoRectangle logical_rect;
};

struct _PangoLayoutClass
{
  GObjectClass parent_class;


};

#define LINE_IS_VALID(line) ((line) && (line)->layout != NULL)

#ifdef G_DISABLE_CHECKS
#define ITER_IS_INVALID(iter) FALSE
#else
#define ITER_IS_INVALID(iter) G_UNLIKELY (check_invalid ((iter), G_STRLOC))
static gboolean
check_invalid (PangoLayoutIter *iter,
	       const char      *loc)
{
  if (iter->line->layout == NULL)
    {
      g_warning ("%s: PangoLayout changed since PangoLayoutIter was created, iterator invalid", loc);
      return TRUE;
    }
  else
    {
      return FALSE;
    }
}
#endif

static void check_context_changed  (PangoLayout *layout);
static void layout_changed  (PangoLayout *layout);

static void pango_layout_clear_lines (PangoLayout *layout);
static void pango_layout_check_lines (PangoLayout *layout);

static PangoAttrList *pango_layout_get_effective_attributes (PangoLayout *layout);

static PangoLayoutLine * pango_layout_line_new         (PangoLayout     *layout);
static void              pango_layout_line_postprocess (PangoLayoutLine *line,
							ParaBreakState  *state,
							gboolean         wrapped);

static int *pango_layout_line_get_log2vis_map (PangoLayoutLine  *line,
					       gboolean          strong);
static int *pango_layout_line_get_vis2log_map (PangoLayoutLine  *line,
					       gboolean          strong);
static void pango_layout_line_leaked (PangoLayoutLine *line);

/* doesn't leak line */
static PangoLayoutLine* _pango_layout_iter_get_line (PangoLayoutIter *iter);

static void pango_layout_get_item_properties (PangoItem      *item,
					      ItemProperties *properties);

static void pango_layout_get_empty_extents_at_index (PangoLayout    *layout,
						     int             index,
						     PangoRectangle *logical_rect);

static void pango_layout_finalize    (GObject          *object);

G_DEFINE_TYPE (PangoLayout, pango_layout, G_TYPE_OBJECT)

static void
pango_layout_init (PangoLayout *layout)
{
  layout->serial = 1;
  layout->attrs = NULL;
  layout->font_desc = NULL;
  layout->text = NULL;
  layout->length = 0;
  layout->width = -1;
  layout->height = -1;
  layout->indent = 0;
  layout->spacing = 0;

  layout->alignment = PANGO_ALIGN_LEFT;
  layout->justify = FALSE;
  layout->auto_dir = TRUE;

  layout->log_attrs = NULL;
  layout->lines = NULL;
  layout->line_count = 0;

  layout->tab_width = -1;
  layout->unknown_glyphs_count = -1;

  layout->wrap = PANGO_WRAP_WORD;
  layout->is_wrapped = FALSE;
  layout->ellipsize = PANGO_ELLIPSIZE_NONE;
  layout->is_ellipsized = FALSE;
}

static void
pango_layout_class_init (PangoLayoutClass *klass)
{
  GObjectClass *object_class = G_OBJECT_CLASS (klass);

  object_class->finalize = pango_layout_finalize;
}

static void
pango_layout_finalize (GObject *object)
{
  PangoLayout *layout;

  layout = PANGO_LAYOUT (object);

  pango_layout_clear_lines (layout);

  if (layout->context)
    g_object_unref (layout->context);

  if (layout->attrs)
    pango_attr_list_unref (layout->attrs);

  g_free (layout->text);

  if (layout->font_desc)
    pango_font_description_free (layout->font_desc);

  if (layout->tabs)
    pango_tab_array_free (layout->tabs);

  G_OBJECT_CLASS (pango_layout_parent_class)->finalize (object);
}


/**
 * pango_layout_new:
 * @context: a #PangoContext
 *
 * Create a new #PangoLayout object with attributes initialized to
 * default values for a particular #PangoContext.
 *
 * Return value: the newly allocated #PangoLayout, with a reference
 *               count of one, which should be freed with
 *               g_object_unref().
 **/
PangoLayout *
pango_layout_new (PangoContext *context)
{
  PangoLayout *layout;

  g_return_val_if_fail (context != NULL, NULL);

  layout = g_object_new (PANGO_TYPE_LAYOUT, NULL);

  layout->context = context;
  layout->context_serial = pango_context_get_serial (context);
  g_object_ref (context);

  return layout;
}

/**
 * pango_layout_copy:
 * @src: a #PangoLayout
 *
 * Does a deep copy-by-value of the @src layout. The attribute list,
 * tab array, and text from the original layout are all copied by
 * value.
 *
 * Return value: (transfer full): the newly allocated #PangoLayout,
 *               with a reference count of one, which should be freed
 *               with g_object_unref().
 **/
PangoLayout*
pango_layout_copy (PangoLayout *src)
{
  PangoLayout *layout;

  g_return_val_if_fail (PANGO_IS_LAYOUT (src), NULL);

  /* Copy referenced members */

  layout = pango_layout_new (src->context);
  if (src->attrs)
    layout->attrs = pango_attr_list_copy (src->attrs);
  if (src->font_desc)
    layout->font_desc = pango_font_description_copy (src->font_desc);
  if (src->tabs)
    layout->tabs = pango_tab_array_copy (src->tabs);

  /* Dupped */
  layout->text = g_strdup (src->text);

  /* Value fields */
  memcpy (&layout->copy_begin, &src->copy_begin,
	  G_STRUCT_OFFSET (PangoLayout, copy_end) - G_STRUCT_OFFSET (PangoLayout, copy_begin));

  return layout;
}

/**
 * pango_layout_get_context:
 * @layout: a #PangoLayout
 *
 * Retrieves the #PangoContext used for this layout.
 *
 * Return value: (transfer none): the #PangoContext for the layout.
 * This does not have an additional refcount added, so if you want to
 * keep a copy of this around, you must reference it yourself.
 **/
PangoContext *
pango_layout_get_context (PangoLayout *layout)
{
  g_return_val_if_fail (layout != NULL, NULL);

  return layout->context;
}

/**
 * pango_layout_set_width:
 * @layout: a #PangoLayout.
 * @width: the desired width in Pango units, or -1 to indicate that no
 *         wrapping or ellipsization should be performed.
 *
 * Sets the width to which the lines of the #PangoLayout should wrap or
 * ellipsized.  The default value is -1: no width set.
 **/
void
pango_layout_set_width (PangoLayout *layout,
			int          width)
{
  g_return_if_fail (layout != NULL);

  if (width < 0)
    width = -1;

  if (width != layout->width)
    {
      layout->width = width;
      layout_changed (layout);
    }
}

/**
 * pango_layout_get_width:
 * @layout: a #PangoLayout
 *
 * Gets the width to which the lines of the #PangoLayout should wrap.
 *
 * Return value: the width in Pango units, or -1 if no width set.
 **/
int
pango_layout_get_width (PangoLayout    *layout)
{
  g_return_val_if_fail (layout != NULL, 0);
  return layout->width;
}

/**
 * pango_layout_set_height:
 * @layout: a #PangoLayout.
 * @height: the desired height of the layout in Pango units if positive,
 *          or desired number of lines if negative.
 *
 * Sets the height to which the #PangoLayout should be ellipsized at.  There
 * are two different behaviors, based on whether @height is positive or
 * negative.
 *
 * If @height is positive, it will be the maximum height of the layout.  Only
 * lines would be shown that would fit, and if there is any text omitted,
 * an ellipsis added.  At least one line is included in each paragraph regardless
 * of how small the height value is.  A value of zero will render exactly one
 * line for the entire layout.
 *
 * If @height is negative, it will be the (negative of) maximum number of lines per
 * paragraph.  That is, the total number of lines shown may well be more than
 * this value if the layout contains multiple paragraphs of text.
 * The default value of -1 means that first line of each paragraph is ellipsized.
 * This behvaior may be changed in the future to act per layout instead of per
 * paragraph.  File a bug against pango at <ulink
 * url="http://bugzilla.gnome.org/">http://bugzilla.gnome.org/</ulink> if your
 * code relies on this behavior.
 *
 * Height setting only has effect if a positive width is set on
 * @layout and ellipsization mode of @layout is not %PANGO_ELLIPSIZE_NONE.
 * The behavior is undefined if a height other than -1 is set and
 * ellipsization mode is set to %PANGO_ELLIPSIZE_NONE, and may change in the
 * future.
 *
 * Since: 1.20
 **/
void
pango_layout_set_height (PangoLayout *layout,
			 int          height)
{
  g_return_if_fail (layout != NULL);

  if (height != layout->height)
    {
      layout->height = height;

      /* Do not invalidate if the number of lines requested is
       * larger than the total number of lines in layout.
       * Bug 549003
       */
      if (layout->ellipsize != PANGO_ELLIPSIZE_NONE &&
	  !(layout->lines && layout->is_ellipsized == FALSE &&
	    height < 0 && layout->line_count <= (guint) -height))
	layout_changed (layout);
    }
}

/**
 * pango_layout_get_height:
 * @layout: a #PangoLayout
 *
 * Gets the height of layout used for ellipsization.  See
 * pango_layout_set_height() for details.
 *
 * Return value: the height, in Pango units if positive, or
 * number of lines if negative.
 *
 * Since: 1.20
 **/
int
pango_layout_get_height (PangoLayout    *layout)
{
  g_return_val_if_fail (layout != NULL, 0);
  return layout->height;
}

/**
 * pango_layout_set_wrap:
 * @layout: a #PangoLayout
 * @wrap: the wrap mode
 *
 * Sets the wrap mode; the wrap mode only has effect if a width
 * is set on the layout with pango_layout_set_width().
 * To turn off wrapping, set the width to -1.
 **/
void
pango_layout_set_wrap (PangoLayout  *layout,
		       PangoWrapMode wrap)
{
  g_return_if_fail (PANGO_IS_LAYOUT (layout));

  if (layout->wrap != wrap)
    {
      layout->wrap = wrap;

      if (layout->width != -1)
	layout_changed (layout);
    }
}

/**
 * pango_layout_get_wrap:
 * @layout: a #PangoLayout
 *
 * Gets the wrap mode for the layout.
 *
 * Use pango_layout_is_wrapped() to query whether any paragraphs
 * were actually wrapped.
 *
 * Return value: active wrap mode.
 **/
PangoWrapMode
pango_layout_get_wrap (PangoLayout *layout)
{
  g_return_val_if_fail (PANGO_IS_LAYOUT (layout), 0);

  return layout->wrap;
}

/**
 * pango_layout_is_wrapped:
 * @layout: a #PangoLayout
 *
 * Queries whether the layout had to wrap any paragraphs.
 *
 * This returns %TRUE if a positive width is set on @layout,
 * ellipsization mode of @layout is set to %PANGO_ELLIPSIZE_NONE,
 * and there are paragraphs exceeding the layout width that have
 * to be wrapped.
 *
 * Return value: %TRUE if any paragraphs had to be wrapped, %FALSE
 * otherwise.
 *
 * Since: 1.16
 */
gboolean
pango_layout_is_wrapped (PangoLayout *layout)
{
  g_return_val_if_fail (layout != NULL, FALSE);

  pango_layout_check_lines (layout);

  return layout->is_wrapped;
}

/**
 * pango_layout_set_indent:
 * @layout: a #PangoLayout.
 * @indent: the amount by which to indent.
 *
 * Sets the width in Pango units to indent each paragraph. A negative value
 * of @indent will produce a hanging indentation. That is, the first line will
 * have the full width, and subsequent lines will be indented by the
 * absolute value of @indent.
 *
 * The indent setting is ignored if layout alignment is set to
 * %PANGO_ALIGN_CENTER.
 **/
void
pango_layout_set_indent (PangoLayout *layout,
			 int          indent)
{
  g_return_if_fail (layout != NULL);

  if (indent != layout->indent)
    {
      layout->indent = indent;
      layout_changed (layout);
    }
}

/**
 * pango_layout_get_indent:
 * @layout: a #PangoLayout
 *
 * Gets the paragraph indent width in Pango units. A negative value
 * indicates a hanging indentation.
 *
 * Return value: the indent in Pango units.
 **/
int
pango_layout_get_indent (PangoLayout *layout)
{
  g_return_val_if_fail (layout != NULL, 0);
  return layout->indent;
}

/**
 * pango_layout_set_spacing:
 * @layout: a #PangoLayout.
 * @spacing: the amount of spacing
 *
 * Sets the amount of spacing in Pango unit between the lines of the
 * layout.
 **/
void
pango_layout_set_spacing (PangoLayout *layout,
			  int          spacing)
{
  g_return_if_fail (layout != NULL);

  if (spacing != layout->spacing)
    {
      layout->spacing = spacing;
      layout_changed (layout);
    }
}

/**
 * pango_layout_get_spacing:
 * @layout: a #PangoLayout
 *
 * Gets the amount of spacing between the lines of the layout.
 *
 * Return value: the spacing in Pango units.
 **/
int
pango_layout_get_spacing (PangoLayout *layout)
{
  g_return_val_if_fail (layout != NULL, 0);
  return layout->spacing;
}

/**
 * pango_layout_set_attributes:
 * @layout: a #PangoLayout
 * @attrs: (allow-none) (transfer none): a #PangoAttrList, can be %NULL
 *
 * Sets the text attributes for a layout object.
 * References @attrs, so the caller can unref its reference.
 **/
void
pango_layout_set_attributes (PangoLayout   *layout,
			     PangoAttrList *attrs)
{
  PangoAttrList *old_attrs;
  g_return_if_fail (layout != NULL);

  old_attrs = layout->attrs;

  /* We always clear lines such that this function can be called
   * whenever attrs changes.
   */

  layout->attrs = attrs;
  if (layout->attrs)
    pango_attr_list_ref (layout->attrs);

  layout_changed (layout);

  if (old_attrs)
    pango_attr_list_unref (old_attrs);
  layout->tab_width = -1;
}

/**
 * pango_layout_get_attributes:
 * @layout: a #PangoLayout
 *
 * Gets the attribute list for the layout, if any.
 *
 * Return value: (transfer none): a #PangoAttrList.
 **/
PangoAttrList*
pango_layout_get_attributes (PangoLayout *layout)
{
  g_return_val_if_fail (PANGO_IS_LAYOUT (layout), NULL);

  return layout->attrs;
}

/**
 * pango_layout_set_font_description:
 * @layout: a #PangoLayout
 * @desc: (allow-none): the new #PangoFontDescription, or %NULL to unset the
 *        current font description
 *
 * Sets the default font description for the layout. If no font
 * description is set on the layout, the font description from
 * the layout's context is used.
 **/
void
pango_layout_set_font_description (PangoLayout                 *layout,
				    const PangoFontDescription *desc)
{
  g_return_if_fail (layout != NULL);

  if (desc != layout->font_desc &&
      (!desc || !layout->font_desc || !pango_font_description_equal(desc, layout->font_desc)))
    {
      if (layout->font_desc)
	pango_font_description_free (layout->font_desc);

      layout->font_desc = desc ? pango_font_description_copy (desc) : NULL;

      layout_changed (layout);
      layout->tab_width = -1;
    }
}

/**
 * pango_layout_get_font_description:
 * @layout: a #PangoLayout
 *
 * Gets the font description for the layout, if any.
 *
 * Return value: (nullable): a pointer to the layout's font
 *  description, or %NULL if the font description from the layout's
 *  context is inherited. This value is owned by the layout and must
 *  not be modified or freed.
 *
 * Since: 1.8
 **/
const PangoFontDescription *
pango_layout_get_font_description (PangoLayout *layout)
{
  g_return_val_if_fail (PANGO_IS_LAYOUT (layout), NULL);

  return layout->font_desc;
}

/**
 * pango_layout_set_justify:
 * @layout: a #PangoLayout
 * @justify: whether the lines in the layout should be justified.
 *
 * Sets whether each complete line should be stretched to
 * fill the entire width of the layout. This stretching is typically
 * done by adding whitespace, but for some scripts (such as Arabic),
 * the justification may be done in more complex ways, like extending
 * the characters.
 *
 * Note that this setting is not implemented and so is ignored in Pango
 * older than 1.18.
 **/
void
pango_layout_set_justify (PangoLayout *layout,
			  gboolean     justify)
{
  g_return_if_fail (layout != NULL);

  if (justify != layout->justify)
    {
      layout->justify = justify;

      if (layout->is_ellipsized || layout->is_wrapped)
	layout_changed (layout);
    }
}

/**
 * pango_layout_get_justify:
 * @layout: a #PangoLayout
 *
 * Gets whether each complete line should be stretched to fill the entire
 * width of the layout.
 *
 * Return value: the justify.
 **/
gboolean
pango_layout_get_justify (PangoLayout *layout)
{
  g_return_val_if_fail (layout != NULL, FALSE);
  return layout->justify;
}

/**
 * pango_layout_set_auto_dir:
 * @layout: a #PangoLayout
 * @auto_dir: if %TRUE, compute the bidirectional base direction
 *   from the layout's contents.
 *
 * Sets whether to calculate the bidirectional base direction
 * for the layout according to the contents of the layout;
 * when this flag is on (the default), then paragraphs in
   @layout that begin with strong right-to-left characters
 * (Arabic and Hebrew principally), will have right-to-left
 * layout, paragraphs with letters from other scripts will
 * have left-to-right layout. Paragraphs with only neutral
 * characters get their direction from the surrounding paragraphs.
 *
 * When %FALSE, the choice between left-to-right and
 * right-to-left layout is done according to the base direction
 * of the layout's #PangoContext. (See pango_context_set_base_dir()).
 *
 * When the auto-computed direction of a paragraph differs from the
 * base direction of the context, the interpretation of
 * %PANGO_ALIGN_LEFT and %PANGO_ALIGN_RIGHT are swapped.
 *
 * Since: 1.4
 **/
void
pango_layout_set_auto_dir (PangoLayout *layout,
			   gboolean     auto_dir)
{
  g_return_if_fail (PANGO_IS_LAYOUT (layout));

  auto_dir = auto_dir != FALSE;

  if (auto_dir != layout->auto_dir)
    {
      layout->auto_dir = auto_dir;
      layout_changed (layout);
    }
}

/**
 * pango_layout_get_auto_dir:
 * @layout: a #PangoLayout
 *
 * Gets whether to calculate the bidirectional base direction
 * for the layout according to the contents of the layout.
 * See pango_layout_set_auto_dir().
 *
 * Return value: %TRUE if the bidirectional base direction
 *   is computed from the layout's contents, %FALSE otherwise.
 *
 * Since: 1.4
 **/
gboolean
pango_layout_get_auto_dir (PangoLayout *layout)
{
  g_return_val_if_fail (PANGO_IS_LAYOUT (layout), FALSE);

  return layout->auto_dir;
}

/**
 * pango_layout_set_alignment:
 * @layout: a #PangoLayout
 * @alignment: the alignment
 *
 * Sets the alignment for the layout: how partial lines are
 * positioned within the horizontal space available.
 **/
void
pango_layout_set_alignment (PangoLayout   *layout,
			    PangoAlignment alignment)
{
  g_return_if_fail (layout != NULL);

  if (alignment != layout->alignment)
    {
      layout->alignment = alignment;
      layout_changed (layout);
    }
}

/**
 * pango_layout_get_alignment:
 * @layout: a #PangoLayout
 *
 * Gets the alignment for the layout: how partial lines are
 * positioned within the horizontal space available.
 *
 * Return value: the alignment.
 **/
PangoAlignment
pango_layout_get_alignment (PangoLayout *layout)
{
  g_return_val_if_fail (layout != NULL, PANGO_ALIGN_LEFT);
  return layout->alignment;
}


/**
 * pango_layout_set_tabs:
 * @layout: a #PangoLayout
 * @tabs: (allow-none): a #PangoTabArray, or %NULL
 *
 * Sets the tabs to use for @layout, overriding the default tabs
 * (by default, tabs are every 8 spaces). If @tabs is %NULL, the default
 * tabs are reinstated. @tabs is copied into the layout; you must
 * free your copy of @tabs yourself.
 **/
void
pango_layout_set_tabs (PangoLayout   *layout,
		       PangoTabArray *tabs)
{
  g_return_if_fail (PANGO_IS_LAYOUT (layout));


  if (tabs != layout->tabs)
    {
      if (layout->tabs)
	pango_tab_array_free (layout->tabs);

      layout->tabs = tabs ? pango_tab_array_copy (tabs) : NULL;

      layout_changed (layout);
    }
}

/**
 * pango_layout_get_tabs:
 * @layout: a #PangoLayout
 *
 * Gets the current #PangoTabArray used by this layout. If no
 * #PangoTabArray has been set, then the default tabs are in use
 * and %NULL is returned. Default tabs are every 8 spaces.
 * The return value should be freed with pango_tab_array_free().
 *
 * Return value: (nullable): a copy of the tabs for this layout, or
 * %NULL.
 **/
PangoTabArray*
pango_layout_get_tabs (PangoLayout *layout)
{
  g_return_val_if_fail (PANGO_IS_LAYOUT (layout), NULL);

  if (layout->tabs)
    return pango_tab_array_copy (layout->tabs);
  else
    return NULL;
}

/**
 * pango_layout_set_single_paragraph_mode:
 * @layout: a #PangoLayout
 * @setting: new setting
 *
 * If @setting is %TRUE, do not treat newlines and similar characters
 * as paragraph separators; instead, keep all text in a single paragraph,
 * and display a glyph for paragraph separator characters. Used when
 * you want to allow editing of newlines on a single text line.
 **/
void
pango_layout_set_single_paragraph_mode (PangoLayout *layout,
					gboolean     setting)
{
  g_return_if_fail (PANGO_IS_LAYOUT (layout));

  setting = setting != FALSE;

  if (layout->single_paragraph != setting)
    {
      layout->single_paragraph = setting;
      layout_changed (layout);
    }
}

/**
 * pango_layout_get_single_paragraph_mode:
 * @layout: a #PangoLayout
 *
 * Obtains the value set by pango_layout_set_single_paragraph_mode().
 *
 * Return value: %TRUE if the layout does not break paragraphs at
 * paragraph separator characters, %FALSE otherwise.
 **/
gboolean
pango_layout_get_single_paragraph_mode (PangoLayout *layout)
{
  g_return_val_if_fail (PANGO_IS_LAYOUT (layout), FALSE);

  return layout->single_paragraph;
}

/**
 * pango_layout_set_ellipsize:
 * @layout: a #PangoLayout
 * @ellipsize: the new ellipsization mode for @layout
 *
 * Sets the type of ellipsization being performed for @layout.
 * Depending on the ellipsization mode @ellipsize text is
 * removed from the start, middle, or end of text so they
 * fit within the width and height of layout set with
 * pango_layout_set_width() and pango_layout_set_height().
 *
 * If the layout contains characters such as newlines that
 * force it to be layed out in multiple paragraphs, then whether
 * each paragraph is ellipsized separately or the entire layout
 * is ellipsized as a whole depends on the set height of the layout.
 * See pango_layout_set_height() for details.
 *
 * Since: 1.6
 **/
void
pango_layout_set_ellipsize (PangoLayout        *layout,
			    PangoEllipsizeMode  ellipsize)
{
  g_return_if_fail (PANGO_IS_LAYOUT (layout));

  if (ellipsize != layout->ellipsize)
    {
      layout->ellipsize = ellipsize;

      if (layout->is_ellipsized || layout->is_wrapped)
	layout_changed (layout);
    }
}

/**
 * pango_layout_get_ellipsize:
 * @layout: a #PangoLayout
 *
 * Gets the type of ellipsization being performed for @layout.
 * See pango_layout_set_ellipsize()
 *
 * Return value: the current ellipsization mode for @layout.
 *
 * Use pango_layout_is_ellipsized() to query whether any paragraphs
 * were actually ellipsized.
 *
 * Since: 1.6
 **/
PangoEllipsizeMode
pango_layout_get_ellipsize (PangoLayout *layout)
{
  g_return_val_if_fail (PANGO_IS_LAYOUT (layout), PANGO_ELLIPSIZE_NONE);

  return layout->ellipsize;
}

/**
 * pango_layout_is_ellipsized:
 * @layout: a #PangoLayout
 *
 * Queries whether the layout had to ellipsize any paragraphs.
 *
 * This returns %TRUE if the ellipsization mode for @layout
 * is not %PANGO_ELLIPSIZE_NONE, a positive width is set on @layout,
 * and there are paragraphs exceeding that width that have to be
 * ellipsized.
 *
 * Return value: %TRUE if any paragraphs had to be ellipsized, %FALSE
 * otherwise.
 *
 * Since: 1.16
 */
gboolean
pango_layout_is_ellipsized (PangoLayout *layout)
{
  g_return_val_if_fail (layout != NULL, FALSE);

  pango_layout_check_lines (layout);

  return layout->is_ellipsized;
}

/**
 * pango_layout_set_text:
 * @layout: a #PangoLayout
 * @text: a valid UTF-8 string
 * @length: maximum length of @text, in bytes. -1 indicates that
 *          the string is nul-terminated and the length should be
 *          calculated.  The text will also be truncated on
 *          encountering a nul-termination even when @length is
 *          positive.
 *
 * Sets the text of the layout.
 *
 * Note that if you have used
 * pango_layout_set_markup() or pango_layout_set_markup_with_accel() on
 * @layout before, you may want to call pango_layout_set_attributes() to clear
 * the attributes set on the layout from the markup as this function does not
 * clear attributes.
 **/
void
pango_layout_set_text (PangoLayout *layout,
		       const char  *text,
		       int          length)
{
  char *old_text, *start, *end;

  g_return_if_fail (layout != NULL);
  g_return_if_fail (length == 0 || text != NULL);

  old_text = layout->text;

  if (length < 0)
    layout->text = g_strdup (text);
  else if (length > 0)
    /* This is not exactly what we want.  We don't need the padding...
     */
    layout->text = g_strndup (text, length);
  else
    layout->text = g_malloc0 (1);

  layout->length = strlen (layout->text);

  /* validate it, and replace invalid bytes with '?'
   */
  start = layout->text;
  for (;;) {
    gboolean valid;

    valid = g_utf8_validate (start, -1, (const char **)&end);

    if (!*end)
      break;

    /* Replace invalid bytes with -1.  The -1 will be converted to
     * ((gunichar) -1) by glib, and that in turn yields a glyph value of
     * ((PangoGlyph) -1) by PANGO_GET_UNKNOWN_GLYPH(-1),
     * and that's PANGO_GLYPH_INVALID_INPUT.
     */
    if (!valid)
      *end++ = -1;

    start = end;
  }

  if (start != layout->text)
    /* TODO: Write out the beginning excerpt of text? */
    g_warning ("Invalid UTF-8 string passed to pango_layout_set_text()");

  layout->n_chars = pango_utf8_strlen (layout->text, -1);

  layout_changed (layout);

  g_free (old_text);
}

/**
 * pango_layout_get_text:
 * @layout: a #PangoLayout
 *
 * Gets the text in the layout. The returned text should not
 * be freed or modified.
 *
 * Return value: the text in the @layout.
 **/
const char*
pango_layout_get_text (PangoLayout *layout)
{
  g_return_val_if_fail (PANGO_IS_LAYOUT (layout), NULL);

  /* We don't ever want to return NULL as the text.
   */
  if (G_UNLIKELY (!layout->text))
    return "";

  return layout->text;
}

/**
 * pango_layout_get_character_count:
 * @layout: a #PangoLayout
 *
 * Returns the number of Unicode characters in the
 * the text of @layout.
 *
 * Return value: the number of Unicode characters
 *     in the text of @layout
 *
 * Since: 1.30
 */
gint
pango_layout_get_character_count (PangoLayout *layout)
{
  g_return_val_if_fail (PANGO_IS_LAYOUT (layout), 0);

  return layout->n_chars;
}

/**
 * pango_layout_set_markup:
 * @layout: a #PangoLayout
 * @markup: marked-up text
 * @length: length of marked-up text in bytes, or -1 if @markup is
 *          null-terminated
 *
 * Same as pango_layout_set_markup_with_accel(), but
 * the markup text isn't scanned for accelerators.
 *
 **/
void
pango_layout_set_markup (PangoLayout *layout,
			 const char  *markup,
			 int          length)
{
  pango_layout_set_markup_with_accel (layout, markup, length, 0, NULL);
}

/**
 * pango_layout_set_markup_with_accel:
 * @layout: a #PangoLayout
 * @markup: marked-up text
 * (see <link linkend="PangoMarkupFormat">markup format</link>)
 * @length: length of marked-up text in bytes, or -1 if @markup is
 *          null-terminated
 * @accel_marker: marker for accelerators in the text
 * @accel_char: (out caller-allocates) (allow-none): return location
 *                    for first located accelerator, or %NULL
 *
 * Sets the layout text and attribute list from marked-up text (see
 * <link linkend="PangoMarkupFormat">markup format</link>). Replaces
 * the current text and attribute list.
 *
 * If @accel_marker is nonzero, the given character will mark the
 * character following it as an accelerator. For example, @accel_marker
 * might be an ampersand or underscore. All characters marked
 * as an accelerator will receive a %PANGO_UNDERLINE_LOW attribute,
 * and the first character so marked will be returned in @accel_char.
 * Two @accel_marker characters following each other produce a single
 * literal @accel_marker character.
 **/
void
pango_layout_set_markup_with_accel (PangoLayout    *layout,
				    const char     *markup,
				    int             length,
				    gunichar        accel_marker,
				    gunichar       *accel_char)
{
  PangoAttrList *list = NULL;
  char *text = NULL;
  GError *error;

  g_return_if_fail (PANGO_IS_LAYOUT (layout));
  g_return_if_fail (markup != NULL);

  error = NULL;
  if (!pango_parse_markup (markup, length,
			   accel_marker,
			   &list, &text,
			   accel_char,
			   &error))
    {
      g_warning ("pango_layout_set_markup_with_accel: %s", error->message);
      g_error_free (error);
      return;
    }

  pango_layout_set_text (layout, text, -1);
  pango_layout_set_attributes (layout, list);
  pango_attr_list_unref (list);
  g_free (text);
}

/**
 * pango_layout_get_unknown_glyphs_count:
 * @layout: a #PangoLayout
 *
 * Counts the number unknown glyphs in @layout.  That is, zero if
 * glyphs for all characters in the layout text were found, or more
 * than zero otherwise.
 *
 * This function can be used to determine if there are any fonts
 * available to render all characters in a certain string, or when
 * used in combination with %PANGO_ATTR_FALLBACK, to check if a
 * certain font supports all the characters in the string.
 *
 * Return value: The number of unknown glyphs in @layout.
 *
 * Since: 1.16
 */
int
pango_layout_get_unknown_glyphs_count (PangoLayout *layout)
{
    PangoLayoutLine *line;
    PangoLayoutRun *run;
    GSList *lines_list;
    GSList *runs_list;
    int i, count = 0;

    g_return_val_if_fail (PANGO_IS_LAYOUT (layout), 0);

    pango_layout_check_lines (layout);

    if (layout->unknown_glyphs_count >= 0)
      return layout->unknown_glyphs_count;

    lines_list = layout->lines;
    while (lines_list)
      {
	line = lines_list->data;
	runs_list = line->runs;

	while (runs_list)
	  {
	    run = runs_list->data;

	    for (i = 0; i < run->glyphs->num_glyphs; i++)
	      {
		if (run->glyphs->glyphs[i].glyph & PANGO_GLYPH_UNKNOWN_FLAG)
		    count++;
	      }

	    runs_list = runs_list->next;
	  }
	lines_list = lines_list->next;
      }

    layout->unknown_glyphs_count = count;
    return count;
}

static void
check_context_changed (PangoLayout *layout)
{
  guint old_serial = layout->context_serial;

  layout->context_serial = pango_context_get_serial (layout->context);

  if (old_serial != layout->context_serial)
    pango_layout_context_changed (layout);
}

static void
layout_changed (PangoLayout *layout)
{
  layout->serial++;
  if (layout->serial == 0)
    layout->serial++;
  pango_layout_clear_lines (layout);
}

/**
 * pango_layout_context_changed:
 * @layout: a #PangoLayout
 *
 * Forces recomputation of any state in the #PangoLayout that
 * might depend on the layout's context. This function should
 * be called if you make changes to the context subsequent
 * to creating the layout.
 **/
void
pango_layout_context_changed (PangoLayout *layout)
{
  g_return_if_fail (PANGO_IS_LAYOUT (layout));

  layout_changed (layout);
  layout->tab_width = -1;
}

/**
 * pango_layout_get_serial:
 * @layout: a #PangoLayout
 *
 * Returns the current serial number of @layout.  The serial number is
 * initialized to an small number  larger than zero when a new layout
 * is created and is increased whenever the layout is changed using any
 * of the setter functions, or the #PangoContext it uses has changed.
 * The serial may wrap, but will never have the value 0. Since it
 * can wrap, never compare it with "less than", always use "not equals".
 *
 * This can be used to automatically detect changes to a #PangoLayout, and
 * is useful for example to decide whether a layout needs redrawing.
 * To force the serial to be increased, use pango_layout_context_changed().
 *
 * Return value: The current serial number of @layout.
 *
 * Since: 1.32.4
 **/
guint
pango_layout_get_serial (PangoLayout *layout)
{
  check_context_changed (layout);
  return layout->serial;
}

/**
 * pango_layout_get_log_attrs:
 * @layout: a #PangoLayout
 * @attrs: (out)(array length=n_attrs)(transfer container):
 *         location to store a pointer to an array of logical attributes
 *         This value must be freed with g_free().
 * @n_attrs: (out): location to store the number of the attributes in the
 *           array. (The stored value will be one more than the total number
 *           of characters in the layout, since there need to be attributes
 *           corresponding to both the position before the first character
 *           and the position after the last character.)
 *
 * Retrieves an array of logical attributes for each character in
 * the @layout.
 **/
void
pango_layout_get_log_attrs (PangoLayout    *layout,
			    PangoLogAttr  **attrs,
			    gint           *n_attrs)
{
  g_return_if_fail (layout != NULL);

  pango_layout_check_lines (layout);

  if (attrs)
    {
      *attrs = g_new (PangoLogAttr, layout->n_chars + 1);
      memcpy (*attrs, layout->log_attrs, sizeof(PangoLogAttr) * (layout->n_chars + 1));
    }

  if (n_attrs)
    *n_attrs = layout->n_chars + 1;
}

/**
 * pango_layout_get_log_attrs_readonly:
 * @layout: a #PangoLayout
 * @n_attrs: (out): location to store the number of the attributes in
 *   the array
 *
 * Retrieves an array of logical attributes for each character in
 * the @layout.
 *
 * This is a faster alternative to pango_layout_get_log_attrs().
 * The returned array is part of @layout and must not be modified.
 * Modifying the layout will invalidate the returned array.
 *
 * The number of attributes returned in @n_attrs will be one more
 * than the total number of characters in the layout, since there
 * need to be attributes corresponding to both the position before
 * the first character and the position after the last character.
 *
 * Returns: (array length=n_attrs): an array of logical attributes
 *
 * Since: 1.30
 */
const PangoLogAttr *
pango_layout_get_log_attrs_readonly (PangoLayout *layout,
                                     gint        *n_attrs)
{
  if (n_attrs)
    *n_attrs = 0;
  g_return_val_if_fail (layout != NULL, NULL);

  pango_layout_check_lines (layout);

  if (n_attrs)
    *n_attrs = layout->n_chars + 1;

  return layout->log_attrs;
}


/**
 * pango_layout_get_line_count:
 * @layout: #PangoLayout
 *
 * Retrieves the count of lines for the @layout.
 *
 * Return value: the line count.
 **/
int
pango_layout_get_line_count (PangoLayout   *layout)
{
  g_return_val_if_fail (layout != NULL, 0);

  pango_layout_check_lines (layout);
  return layout->line_count;
}

/**
 * pango_layout_get_lines:
 * @layout: a #PangoLayout
 *
 * Returns the lines of the @layout as a list.
 *
 * Use the faster pango_layout_get_lines_readonly() if you do not plan
 * to modify the contents of the lines (glyphs, glyph widths, etc.).
 *
 * Return value: (element-type Pango.LayoutLine) (transfer none): a #GSList containing
 * the lines in the layout. This points to internal data of the #PangoLayout
 * and must be used with care. It will become invalid on any change to the layout's
 * text or properties.
 **/
GSList *
pango_layout_get_lines (PangoLayout *layout)
{
  pango_layout_check_lines (layout);

  if (layout->lines)
    {
      GSList *tmp_list = layout->lines;
      while (tmp_list)
	{
	  PangoLayoutLine *line = tmp_list->data;
	  tmp_list = tmp_list->next;

	  pango_layout_line_leaked (line);
	}
    }

  return layout->lines;
}

/**
 * pango_layout_get_lines_readonly:
 * @layout: a #PangoLayout
 *
 * Returns the lines of the @layout as a list.
 *
 * This is a faster alternative to pango_layout_get_lines(),
 * but the user is not expected
 * to modify the contents of the lines (glyphs, glyph widths, etc.).
 *
 * Return value: (element-type Pango.LayoutLine) (transfer none): a #GSList containing
 * the lines in the layout. This points to internal data of the #PangoLayout and
 * must be used with care. It will become invalid on any change to the layout's
 * text or properties.  No changes should be made to the lines.
 *
 * Since: 1.16
 **/
GSList *
pango_layout_get_lines_readonly (PangoLayout *layout)
{
  pango_layout_check_lines (layout);

  return layout->lines;
}

/**
 * pango_layout_get_line:
 * @layout: a #PangoLayout
 * @line: the index of a line, which must be between 0 and
 *        <literal>pango_layout_get_line_count(layout) - 1</literal>, inclusive.
 *
 * Retrieves a particular line from a #PangoLayout.
 *
 * Use the faster pango_layout_get_line_readonly() if you do not plan
 * to modify the contents of the line (glyphs, glyph widths, etc.).
 *
 * Return value: (transfer none) (nullable): the requested
 *               #PangoLayoutLine, or %NULL if the index is out of
 *               range. This layout line can be ref'ed and retained,
 *               but will become invalid if changes are made to the
 *               #PangoLayout.
 **/
PangoLayoutLine *
pango_layout_get_line (PangoLayout *layout,
		       int          line)
{
  GSList *list_item;
  g_return_val_if_fail (layout != NULL, NULL);

  if (line < 0)
    return NULL;

  pango_layout_check_lines (layout);

  list_item = g_slist_nth (layout->lines, line);

  if (list_item)
    {
      PangoLayoutLine *line = list_item->data;

      pango_layout_line_leaked (line);
      return line;
    }

  return NULL;
}

/**
 * pango_layout_get_line_readonly:
 * @layout: a #PangoLayout
 * @line: the index of a line, which must be between 0 and
 *        <literal>pango_layout_get_line_count(layout) - 1</literal>, inclusive.
 *
 * Retrieves a particular line from a #PangoLayout.
 *
 * This is a faster alternative to pango_layout_get_line(),
 * but the user is not expected
 * to modify the contents of the line (glyphs, glyph widths, etc.).
 *
 * Return value: (transfer none) (nullable): the requested
 *               #PangoLayoutLine, or %NULL if the index is out of
 *               range. This layout line can be ref'ed and retained,
 *               but will become invalid if changes are made to the
 *               #PangoLayout.  No changes should be made to the line.
 *
 * Since: 1.16
 **/
PangoLayoutLine *
pango_layout_get_line_readonly (PangoLayout *layout,
				int          line)
{
  GSList *list_item;
  g_return_val_if_fail (layout != NULL, NULL);

  if (line < 0)
    return NULL;

  pango_layout_check_lines (layout);

  list_item = g_slist_nth (layout->lines, line);

  if (list_item)
    {
      PangoLayoutLine *line = list_item->data;
      return line;
    }

  return NULL;
}

/**
 * pango_layout_line_index_to_x:
 * @line:     a #PangoLayoutLine
 * @index_:   byte offset of a grapheme within the layout
 * @trailing: an integer indicating the edge of the grapheme to retrieve
 *            the position of. If > 0, the trailing edge of the grapheme,
 *            if 0, the leading of the grapheme.
 * @x_pos: (out): location to store the x_offset (in Pango unit)
 *
 * Converts an index within a line to a X position.
 *
 **/
void
pango_layout_line_index_to_x (PangoLayoutLine  *line,
			      int               index,
			      int               trailing,
			      int              *x_pos)
{
  PangoLayout *layout = line->layout;
  GSList *run_list = line->runs;
  int width = 0;

  while (run_list)
    {
      PangoLayoutRun *run = run_list->data;
      ItemProperties properties;

      pango_layout_get_item_properties (run->item, &properties);

      if (run->item->offset <= index && run->item->offset + run->item->length > index)
	{
	  int offset = g_utf8_pointer_to_offset (layout->text, layout->text + index);
	  if (trailing)
	    {
	      while (index < line->start_index + line->length &&
		     offset + 1 < layout->n_chars &&
		     !layout->log_attrs[offset + 1].is_cursor_position)
		{
		  offset++;
		  index = g_utf8_next_char (layout->text + index) - layout->text;
		}
	    }
	  else
	    {
	      while (index > line->start_index &&
		     !layout->log_attrs[offset].is_cursor_position)
		{
		  offset--;
		  index = g_utf8_prev_char (layout->text + index) - layout->text;
		}

	    }

	  pango_glyph_string_index_to_x (run->glyphs,
					 layout->text + run->item->offset,
					 run->item->length,
					 &run->item->analysis,
					 index - run->item->offset, trailing, x_pos);
	  if (x_pos)
	    *x_pos += width;

	  return;
	}

      width += pango_glyph_string_get_width (run->glyphs);

      run_list = run_list->next;
    }

  if (x_pos)
    *x_pos = width;
}

static PangoLayoutLine *
pango_layout_index_to_line (PangoLayout      *layout,
			    int               index,
			    int              *line_nr,
			    PangoLayoutLine **line_before,
			    PangoLayoutLine **line_after)
{
  GSList *tmp_list;
  GSList *line_list;
  PangoLayoutLine *line = NULL;
  PangoLayoutLine *prev_line = NULL;
  int i = -1;

  line_list = tmp_list = layout->lines;
  while (tmp_list)
    {
      PangoLayoutLine *tmp_line = tmp_list->data;

      if (tmp_line->start_index > index)
	break; /* index was in paragraph delimiters */

      prev_line = line;
      line = tmp_line;
      line_list = tmp_list;
      i++;

      if (line->start_index + line->length > index)
	break;

      tmp_list = tmp_list->next;
    }

  if (line_nr)
    *line_nr = i;

  if (line_before)
    *line_before = prev_line;

  if (line_after)
    *line_after = (line_list && line_list->next) ? line_list->next->data : NULL;

  return line;
}

static PangoLayoutLine *
pango_layout_index_to_line_and_extents (PangoLayout     *layout,
					int              index,
					PangoRectangle  *line_rect)
{
  PangoLayoutIter iter;
  PangoLayoutLine *line = NULL;

  _pango_layout_get_iter (layout, &iter);

  if (!ITER_IS_INVALID (&iter))
    while (TRUE)
      {
	PangoLayoutLine *tmp_line = _pango_layout_iter_get_line (&iter);

	if (tmp_line->start_index > index)
	    break; /* index was in paragraph delimiters */

	line = tmp_line;

	pango_layout_iter_get_line_extents (&iter, NULL, line_rect);

	if (line->start_index + line->length > index)
	  break;

	if (!pango_layout_iter_next_line (&iter))
	  break; /* Use end of last line */
      }

  _pango_layout_iter_destroy (&iter);

  return line;
}

/**
 * pango_layout_index_to_line_x:
 * @layout:    a #PangoLayout
 * @index_:    the byte index of a grapheme within the layout.
 * @trailing:  an integer indicating the edge of the grapheme to retrieve the
 *             position of. If > 0, the trailing edge of the grapheme, if 0,
 *             the leading of the grapheme.
 * @line: (out) (allow-none): location to store resulting line index. (which will
 *               between 0 and pango_layout_get_line_count(layout) - 1), or %NULL
 * @x_pos: (out) (allow-none): location to store resulting position within line
 *              (%PANGO_SCALE units per device unit), or %NULL
 *
 * Converts from byte @index_ within the @layout to line and X position.
 * (X position is measured from the left edge of the line)
 */
void
pango_layout_index_to_line_x (PangoLayout *layout,
			      int          index,
			      gboolean     trailing,
			      int         *line,
			      int         *x_pos)
{
  int line_num;
  PangoLayoutLine *layout_line = NULL;

  g_return_if_fail (layout != NULL);
  g_return_if_fail (index >= 0);
  g_return_if_fail (index <= layout->length);

  pango_layout_check_lines (layout);

  layout_line = pango_layout_index_to_line (layout, index,
					    &line_num, NULL, NULL);

  if (layout_line)
    {
      /* use end of line if index was in the paragraph delimiters */
      if (index > layout_line->start_index + layout_line->length)
	index = layout_line->start_index + layout_line->length;

      if (line)
	*line = line_num;

      pango_layout_line_index_to_x (layout_line, index, trailing, x_pos);
    }
  else
    {
      if (line)
	*line = -1;
      if (x_pos)
	*x_pos = -1;
    }
}

/**
 * pango_layout_move_cursor_visually:
 * @layout:       a #PangoLayout.
 * @strong:       whether the moving cursor is the strong cursor or the
 *                weak cursor. The strong cursor is the cursor corresponding
 *                to text insertion in the base direction for the layout.
 * @old_index:    the byte index of the grapheme for the old index
 * @old_trailing: if 0, the cursor was at the leading edge of the
 *                grapheme indicated by @old_index, if > 0, the cursor
 *                was at the trailing edge.
 * @direction:    direction to move cursor. A negative
 *                value indicates motion to the left.
 * @new_index: (out): location to store the new cursor byte index. A value of -1
 *                indicates that the cursor has been moved off the beginning
 *                of the layout. A value of %G_MAXINT indicates that
 *                the cursor has been moved off the end of the layout.
 * @new_trailing: (out): number of characters to move forward from the
 *                location returned for @new_index to get the position
 *                where the cursor should be displayed. This allows
 *                distinguishing the position at the beginning of one
 *                line from the position at the end of the preceding
 *                line. @new_index is always on the line where the
 *                cursor should be displayed.
 *
 * Computes a new cursor position from an old position and
 * a count of positions to move visually. If @direction is positive,
 * then the new strong cursor position will be one position
 * to the right of the old cursor position. If @direction is negative,
 * then the new strong cursor position will be one position
 * to the left of the old cursor position.
 *
 * In the presence of bidirectional text, the correspondence
 * between logical and visual order will depend on the direction
 * of the current run, and there may be jumps when the cursor
 * is moved off of the end of a run.
 *
 * Motion here is in cursor positions, not in characters, so a
 * single call to pango_layout_move_cursor_visually() may move the
 * cursor over multiple characters when multiple characters combine
 * to form a single grapheme.
 **/
void
pango_layout_move_cursor_visually (PangoLayout *layout,
				   gboolean     strong,
				   int          old_index,
				   int          old_trailing,
				   int          direction,
				   int         *new_index,
				   int         *new_trailing)
{
  PangoLayoutLine *line = NULL;
  PangoLayoutLine *prev_line;
  PangoLayoutLine *next_line;

  int *log2vis_map;
  int *vis2log_map;
  int n_vis;
  int vis_pos, vis_pos_old, log_pos;
  int start_offset;
  gboolean off_start = FALSE;
  gboolean off_end = FALSE;

  g_return_if_fail (layout != NULL);
  g_return_if_fail (old_index >= 0 && old_index <= layout->length);
  g_return_if_fail (old_index < layout->length || old_trailing == 0);
  g_return_if_fail (new_index != NULL);
  g_return_if_fail (new_trailing != NULL);

  direction = (direction >= 0 ? 1 : -1);

  pango_layout_check_lines (layout);

  /* Find the line the old cursor is on */
  line = pango_layout_index_to_line (layout, old_index,
				     NULL, &prev…

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