shape.c

Pango is a library for layout and rendering of text, with an emphasis on internationalization. Pang

/* Pango
 * shape.c: Convert characters into glyphs.
 *
 * Copyright (C) 1999 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.
 */

#include <config.h>

#include "pango-impl-utils.h"
#include "pango-glyph.h"
#include "pango-engine-private.h"

#include <string.h>

/**
 * pango_shape:
 * @text:      the text to process
 * @length:    the length (in bytes) of @text
 * @analysis:  #PangoAnalysis structure from pango_itemize()
 * @glyphs:    glyph string in which to store results
 *
 * Given a segment of text and the corresponding
 * #PangoAnalysis structure returned from pango_itemize(),
 * convert the characters into glyphs. You may also pass
 * in only a substring of the item from pango_itemize().
 */
void
pango_shape (const gchar      *text,
	     gint              length,
	     const PangoAnalysis *analysis,
	     PangoGlyphString *glyphs)
{
  int i;
  int last_cluster;

  glyphs->num_glyphs = 0;

  if (G_LIKELY (analysis->shape_engine && analysis->font))
    {
      _pango_engine_shape_shape (analysis->shape_engine, analysis->font,
				 text, length, analysis, glyphs);

      if (G_UNLIKELY (glyphs->num_glyphs == 0))
	{
	  /* If a font has been correctly chosen, but no glyphs are output,
	   * there's probably something wrong with the shaper, or the font.
	   *
	   * Trying to be informative, we print out the font description,
	   * shaper name, and the text, but to not flood the terminal with
	   * zillions of the message, we set a flag to only err once per
	   * font/engine pair.
	   *
	   * To do the flag fast, we use the engine qname to qflag the font,
	   * but also the font description to flag the engine.  This is
	   * supposed to be fast to check, but also avoid writing out
	   * duplicate warnings when a new PangoFont is created.
	   */
	  GType engine_type = G_OBJECT_TYPE (analysis->shape_engine);
	  GQuark warned_quark = g_type_qname (engine_type);

	  if (!g_object_get_qdata (G_OBJECT (analysis->font), warned_quark))
	    {
	      PangoFontDescription *desc;
	      char *font_name;
	      const char *engine_name;

	      desc = pango_font_describe (analysis->font);
	      font_name = pango_font_description_to_string (desc);
	      pango_font_description_free (desc);

	      if (!g_object_get_data (G_OBJECT (analysis->shape_engine), font_name))
	        {
		  engine_name = g_type_name (engine_type);
		  if (!engine_name)
		    engine_name = "(unknown)";

		  g_warning ("shaping failure, expect ugly output. shape-engine='%s', font='%s', text='%.*s'",
			     engine_name,
			     font_name,
			     length == -1 ? (gint) strlen (text) : length, text);

		  g_object_set_data_full (G_OBJECT (analysis->shape_engine), font_name,
					  GINT_TO_POINTER (1), NULL);
	        }

	      g_free (font_name);

	      g_object_set_qdata_full (G_OBJECT (analysis->font), warned_quark,
				       GINT_TO_POINTER (1), NULL);
	    }
	}
    }
  else
    glyphs->num_glyphs = 0;

  if (!glyphs->num_glyphs)
    {
      PangoEngineShape *fallback_engine = _pango_get_fallback_shaper ();

      _pango_engine_shape_shape (fallback_engine, analysis->font,
				 text, length, analysis, glyphs);
    }

  /* make sure last_cluster is invalid */
  last_cluster = glyphs->log_clusters[0] - 1;
  for (i = 0; i < glyphs->num_glyphs; i++)
    {
     /* Set glyphs[i].attr.is_cluster_start based on log_clusters[]
      */
      if (glyphs->log_clusters[i] != last_cluster)
	{
	  glyphs->glyphs[i].attr.is_cluster_start = TRUE;
	  last_cluster = glyphs->log_clusters[i];
	}
      else
	glyphs->glyphs[i].attr.is_cluster_start = FALSE;


      /* Shift glyph if width is negative, and negate width.
       * This is useful for rotated font matrices and shouldn't
       * harm in normal cases.
       */
      if (glyphs->glyphs[i].geometry.width < 0)
	{
	  glyphs->glyphs[i].geometry.width = -glyphs->glyphs[i].geometry.width;
	  glyphs->glyphs[i].geometry.x_offset += glyphs->glyphs[i].geometry.width;
	}
    }
}